Previous Updates
2025
Update 3-3-25
We continue to track a large marine heatwave denoted as NEP24A (see southern portions of Figures 1 and 2). NEP24A began around ~April 28th, 2024, hence the name which denotes that this heatwave was the first to arise - A - during 2024, although it has continued now into 2025. This heatwave reached its maximum size of ~6 million km2 on Sept 3, 2024, then decreased in size during the fall before reaching its current size (~ 3 million km2). NEP24A currently ranks as the 6th largest by area and 4th longest by duration since satellite monitoring began in 1982. NEP24A is slightly unusual compared to recent similarly large marine heatwaves in that it has lingered into the later winter/spring period in this southern part of the examined region; other similar heatwaves that have lingered into the late winter/spring were generally located to the northwest of this region within the Gulf of Alaska. Coastal sea surface temperatures within the EEZ (exclusive economic zone, denoted by blue dashed line on figures) remain close to the long term average.
The current heatwave forecast suggests NEP24A may continue for the next several months (in the south-central to eastern portion of the region). The El Niño forecast suggests that the La Niña watch status is likely to persist for several more months (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 1-22-25
We continue to track a large marine heatwave denoted as NEP24A (see southern portions of Figures 1 and 2). NEP24A began around ~April 28th, reached its maximum size of ~6 million km^2 on Sept 3, 2024, then decreased in size during the fall before reaching its current size (~ 4 million km^2). Over the past several weeks, however, this heatwave has regained size, and a new heatwave (NEP25A) has developed in the northern part of the region within the Gulf of Alaska (Fig.1). NEP24A currently ranks as the 6th largest by area and 5th longest by duration since satellite monitoring began in 1982. If the heatwave in the northern part of the region persists (NEP25A) and merges with NEP24A, the combined heatwave would encompass much of the northeast Pacific and represent a rather unique and large event for this time of the year. We will present additional analysis of NEP25A once more up-to-date OISST data is available.
The current heatwave forecast suggests that NEP24A may continue for the next several months (in the south-central to eastern portion of the region), whereas NEP25A (to the North) is more likely to dissipate. The El Niño forecast suggests that the La Niña watch status is likely to persist for several more months (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
2024
Update 12-03-24
We continue to track a large (~ 3 million km2 in area currently) marine heatwave (MHW), denoted as NEP24A (Fig. 1 and 2). This MHW began in late April (~April 28th), slowly grew to approximately 3.5 million km2 over the summer, decreased slightly in size during late July, and then expanded to its maximum size during August (~6 million km2 on Sept 3rd), occupying >50% of the west coast Exclusive Economic Zone (EEZ) during late August (Figure 4b; the red shading on the bars indicates > 50% coverage). NEP24A was the 6th largest by area and 7th longest by duration since satellite monitoring began in 1982. This heatwave emerged with the same timing from a similar region far offshore as MHWs have in the past 5 years, and so far this year it has followed the same pattern as previous heatwave events. During October and November, heatwave conditions decreased in the nearshore within the EEZ, while the main body of the heatwave has remained further offshore and is now located in the more southern part of the analyzed region (Fig 1 and 2).
The current heatwave forecast suggests that NEP24A will continue to decline in size and strength over the fall in nearshore regions, following the spatiotemporal pattern described above. whereas heatwaves to the far southwest of the region may continue. The El Niño forecast suggests that a weak La Niña is likely to emerge in October-December 2024 and persist through January-March 2025 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml), a pattern which typically leads to cooler coastal waters. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 10-23-24
We continue to track a large (~ 4 million km2 in area currently) marine heatwave (MHW), denoted as NEP24A (Fig. 1 and 2). This MHW began in late April (~April 28th), slowly grew to approximately 3.5 million km2 over the summer, decreased slightly in size during late July, and then expanded to its maximum size during August (~6 million km2), occupying >50% of the west coast Exclusive Economic Zone (EEZ) during late August (Figure 4b; the red shading on the bars indicates > 50% coverage). NEP24A emerged with the same timing as MHWs have in the previous 5 years from a similar region far offshore. So far this year, this heatwave has followed the pattern seen in previous years and heatwave events. During October, heatwave conditions have decreased in the nearshore within the EEZ, while the main body of the heatwave has remained further offshore and is now located more to the south part of the analyzed region (Fig 1 and 2).
The current heatwave forecast suggests that NEP24A will continue to decline in size and strength over the fall in nearshore regions, following a pattern similar to heatwaves in the past in this area, but may remain in the southern far offshore region. The El Niño forecast suggests that we are in an ENSO neutral state with a possible transition to a La Niña state this winter (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 9-12-24
We continue to track a large (~ 6 million km2 in area) marine heatwave which has expanded into coastal regions during the past several weeks (Fig. 1 and 2). This MHW, denoted as NEP24A, began in late April (~April 28th), slowly grew to approximately 3.5 million km2 over the summer, decreased slightly in size during late July, and then expanded to its current size during August and September, occupying >50% of the west coast Exclusive Economic Zone (EEZ) during late August (Figure 4b; the red shading on the bars indicates > 50% coverage). NEP24A emerged with the same timing as MHWs have in the previous 5 years from a similar region far offshore. So far this year, this heatwave has followed the pattern seen in previous years and heatwave events. With the now widespread intrusion of this heatwave into the coastal region, we may begin to see impacts in coastal waters of the California Current ecosystem.
The current heatwave forecast suggests that we are in an ENSO neutral state and will most likely transition to a La Niña state by September - November of 2024 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 8-19-24
We are tracking a fairly large (~ 2.5 million km^2 in area) marine heatwave which has expanded and moved closer to shore during the past month (Fig. 1 and 2). This MHW, denoted as NEP24A, began in late April (~April 28th), slowly grew to approximately 3.5 million km^2 over the summer, decreased slightly in size during late July, and then expanded to its current size during August (Fig. 4b). NEP24A emerged with the same timing as MHWs have in the previous 5 years and in a similar region far offshore. If the current pattern follows these past events, we can expect NEP24A to possibly grow in size during the next month and likely impact the coastal waters during the fall, particularly in the Pacific Northwest where this heatwave is already fairly close to shore (small portions of it have already intersected the shore off OR/NorCAL). In contrast, most of central California has remained average to cooler than average near the coast due to continued moderate to strong upwelling in those regions.
The current heatwave forecast suggests that the current heatwave will continue for the next several months, at least in the offshore region. The current El Niño forecast suggests that we are in an ENSO neutral state and will most likely transition to a La Niña state by the fall of 2024 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 5-28-24
Although the Pacific is still technically experiencing an El Niño, conditions along the equator show that the strength of the El Niño has been steadily decreasing since Feb. Along the US west coast, sea surface temperature anomalies have returned to values near their climatological averages over the last month (Fig. 1, 2, and 4), reflecting the weakening influence of El Niño in this region. Instead, we have seen fairly strong southward winds, which lead to upwelling and cooling of the surface waters in the coastal region. However, in late April (~April 28th), another large MHW ~2 million km2 in area developed in the far offshore region of our study area. This MHW, denoted as NEP24A, emerged with the same timing as MHWs have in the previous 5 years. If the current pattern follows these past events, we can expect NEP24A to slowly grow in size and possibly impact the coastal waters during the fall.
The current heatwave forecast suggests that there will be only minimal if any warming along the coast during the summer, with likely continued warming in the far offshore region, a pattern consistent with current observations. The current El Niño forecast suggests that we are transitioning towards an ENSO neutral state during May - June and then most likely will transition to a La Niña state by the fall of 2024 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 4-19-24
Although the Pacific is still technically experiencing an El Niño, conditions along the equator show that the strength of the El Niño has decreased (see April 2024 ENSO update: gone fishing | NOAA Climate.gov). Along the US west coast, sea surface temperature anomalies have steadily decreased and are approaching climatological averages over the last month (Fig. 1, 2, and 4), reflecting the weakening influence of El Niño in this region. However, there are still considerable areas of anomalously warm temperatures in pockets along the coast. As in previous years, it is likely that anomalously warm areas in offshore regions to the northwest may develop into a larger heatwave that continues through the summer and into fall, with possible coastal impacts.
The current heatwave forecast suggests that the warming along the coast will most likely subside, consistent with the weakening of the El Niño, although the far offshore northwest area will likely remain warmer than normal through the summer. Current El Niño forecast suggests that we will enter an ENSO neutral state sometime from May - June and then most likely transition to a La Niña state by the fall of 2024 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 3-12-24
The California Current system is currently in an El Niño state, with coastal waters that are warmer than normal for this time of year (Fig. 1 and 2). El Niño can bring a marine heatwave to the CCS, with different drivers and ecological consequences than the “typical”, large, offshore-derived, marine heatwaves usually tracked here. Rather than a single contiguous heatwave, the current sea surface temperature anomaly pattern is much more patchy in distribution, with many smaller fragments scattered throughout the coastal and offshore regions. Hence we are not currently tracking any individual large marine heatwaves (our threshold for tracking individual marine heatwaves is when they cover a contiguous area > 400,000 km2). Instead, we refer to Figure 4b, which shows that within the EEZ, these smaller patchy heatwaves summed together currently cover at least 25% of that area, and had covered > 50% during late Jan/early Feb.
The current heatwave forecast suggests that the warming along the coast has a high probability of persisting through April, with the far offshore remaining warmer than normal through the summer. We continue to be in an “El Niño advisory” status, meaning we are currently in an El Niño state, with a >70% chance that the system will return to a more neutral state sometime from April - June and a similar chance of transitioning back to a La Niña state by the fall of 2024 (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 1-08-24
The California Current system has now transitioned to an El Niño state, with coastal waters that are warmer than normal for this time of year (Fig. 1 and 2). El Niño is essentially another type of marine heatwave, with different drivers and ecological consequences than the “typical” large, offshore-derived marine heatwaves usually tracked here. Of the two previously tracked marine heatwaves, NEP23A, formed in mid-May 2023 and reached its maximum size (~7.6 million km^2) during late September 2023, decreased in area and receded from the coast during October, and fell below our tracking threshold in late November. The second large marine heatwave, NEP23B, which arose in late October in the south-central portion of the region, has essentially merged with the signature of the current coastal warming related to the ongoing El Niño.
The current heatwave forecast suggests that the warming along the coast (essentially NEP23B) has a high probability of persisting for the next few months. We continue to be in an “El Niño advisory” status, meaning we are currently in an El Niño state, with a 55% chance that this El Niño will obtain a “strong” categorization, although a 60% chance that the system will return to a more neutral state sometime from April - June (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
2023
Update 10-04-23
We continue to track marine heatwave NEP23A (Fig. 1 and 2), which formed in mid May 2023 and continues through this current update. NEP23A has decreased in area and receded from much of the coast (Fig. 1), after reaching its maximum size during late September (7.6 million km2). The rapid decrease in size was driven by the combined effects of a strong storm moving across the northern California Current region, and upwelling winds along most of the southern California Current. Relative to past large MHWs, NEP23A was comparable to the 2022 event (NEP22A) and now stands as the 4th largest by area and within the top 20 by duration.
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that coastal waters will continue to cool and NEP2023A will remain offshore through the fall, with an increased risk of coastal warming in the spring of 2024. Furthermore, we are still in an “El Niño advisory” status, with a 95% chance that El Niño will persist through the Northern Hemisphere winter (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). Unlike the events in 2014-2015, the last time this system had a strong marine heatwave with an El Niño looming, the current heatwave appears to be receding rather than building in strength, making it more similar to the heatwaves tracked over the past 4 years. Thus, we expect to see a return to cooler coastal temperatures until the El Niño brings back warmer coastal conditions in the late winter/early spring. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible West Coast impacts.
Update 9–11-23
We are currently tracking marine heatwave (MHW) NEP23A (Fig. 1 and 2), which formed in mid May 2023 and continues through this current update. After a short decrease in size last month, with a brief recession from the coastline, NEP23A has now again increased in area (covering at least 6 million km2, Fig. 4), and has now reached the Canadian and US west coasts (Fig. 1 and 2). and has reemerged along nearly the entire US west coast (Fig. 1,2, and 5). Compared to past large MHWs, NEP23A now stands as the 4th largest by area, and within the top 20 by duration. However, NEP23A formed in the same region where the previous MHW (NEP22A) decreased in size below our area tracking threshold only a few days before this new heatwave arose. Thus, although we denote NEP23A as a “new” heatwave, it is likely an extension of the previous event because it formed in a region where much of the ocean surface temperatures were already elevated above normal, but just below our MHW thresholds.
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that NEP2023A will continue in the offshore waters through the fall, with an increased risk of coastal warming in the spring of 2024. Additionally, we are currently in an “El Niño advisory” status, with a greater than 90% chance that El Niño will persist through the Northern Hemisphere winter (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). El Niño combined with the current large offshore marine heatwave, may indicate the system is heading towards conditions similar to that encountered in 2014-2015, the last period during which we had a similar confluence of these two extremes. However, it is also possible that the heatwave may follow the previous pattern of the last 4 years, which would instead see a weakening of the heatwave and recession further offshore during Oct-Nov. If that is the case, then we expect to see a return to cooler coastal temperatures until the El Niño brings back warmer coastal conditions in the early spring. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Current conditions update 8–8-23
We are currently tracking marine heatwave (MHW) NEP23A, that formed in mid May 2023 and continues through this current update. NEP23A has been increasing in size during the past months, and has now reached the Canadian and US west coasts (Fig. 1 and 2). This large heatwave formed in the same region where the previous MHW (NEP22A) dissipated below our area tracking threshold only a few days before this new heatwave arose. Thus, although we denote NEP23A as a “new” heatwave, it is an extension of the previous event because it formed in a region where much of the ocean surface temperatures were already elevated above normal, but just below our MHW thresholds. Warming off the coast of OR and WA has reached at least 4°C above normal (normal being defined as the average temperature at a specific location for the specific time of year), with the northern coast of CA also seeing some increased warming.*Note that at the time of this update, parts of the current heatwave are warmer than the scale given in Fig.1, with temperatures reaching approximately 5°C above normal (darkest red region in Fig. 1 denotes area that is above scale).
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that NEP2023A will continue in the offshore waters through this summer, with an increased risk of coastal warming in the spring of 2024. Additionally, we are currently in an “El Niño advisory” status, with a greater than 90% chance that El Niño will persist through the Northern Hemisphere winter (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml). El Niño combined with the current large offshore marine heatwave, may indicate the system is heading towards conditions similar to that encountered in 2014-2015, the last period during which we had a similar confluence of these two extremes. However, it is also possible that the heatwave may follow the previous pattern of the last 4 years, which would instead see a weakening of the heatwave and recession further offshore during Oct-Nov. If that is the case, then we expect to see a return to cooler coastal temperatures until the El Niño brings back warmer coastal conditions in the early spring. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Update 7-20-23
We are currently tracking the large marine heatwave (LMH, defined as a contiguous area > 400,000 km2 with temperatures within the top 10% seen for that region on that specific day over the past 40 years), denoted as NEP23A, that formed in mid May 2023 and continues through this current update. NEP23A has been generally increasing in size during the past months, and slowly advancing towards the Canadian and US west coasts (Fig. 1 and 2). This large heatwave formed in the same region where the previous LMH (NEP22A) dissipated below our area tracking threshold only a few days before this new heatwave arose. Thus although we denote NEP23A as a “new” heatwave, it formed in a region where much of the ocean surface temperatures were already elevated above normal, but were just below our thresholds for heatwave tracking, making this new heatwave an extension of that previous event. The previous event, NEP22A, formed in mid Jan 2022, reached its maximum size in August 2022 (becoming the 4th largest marine heatwave by area since monitoring began in 1982) and lasted for 483 days, making it also the 2nd longest heatwave on record.
We also highlight recent coastal warming off central and southern CA (Fig. 2), which is not connected to the large offshore marine heatwave. This warming may be a combination of local forcing, and/or a noted shift in wind patterns in that region leading to lower upwelling (the supply of cold water from below along the coast due to southerly winds), a phenomena that has occurred in other years in this region. The area that is warmer than normal within this coastal region (Fig. 2; the science-quality, time-delayed data used for analysis) is still below our area tracking threshold, but we will continue to monitor this area.
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that NEP2023A will continue in the offshore waters through this summer. Additionally, we are currently in an “El Nino advisory” status, with a greater than 90% chance that El Niño will continue through the Northern Hemisphere winter. (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml) El Niño combined with the current large offshore marine heatwave, may indicate the system is heading towards conditions similar to that encountered in 2014-2015, the last period during which we had a similar confluence of these two extremes. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Update 6-20-23
We are currently tracking the large marine heatwave (LMH, defined as a contiguous area > 400,000 km2 with temperatures within the top 10% seen for that region on that specific day over the past 40 years), denoted as NEP23A, that formed in mid May 2023 and continues through this current update. This large heatwave formed in the same region where the previous LMH (NEP22A) dissipated below our area tracking threshold only a few days before this new heatwave arose. Thus although we denote NEP23A as a “new” heatwave, it formed in a region where much of the ocean surface temperatures were already elevated above normal, but were just below our thresholds for heatwave tracking, making this new heatwave an extension of that previous event. The previous event, NEP22A, formed in mid Jan 2022, reached its maximum size in August 2022 (becoming the 4th largest marine heatwave by area since monitoring began in 1982) and lasted for 483 days, making it also the 2nd longest heatwave on record.
We also highlight recent coastal warming off central and southern CA (Fig. 1), which is not connected to the large offshore marine heatwave. This warming may be a combination of local forcing, and/or a noted shift in wind patterns in that region leading to lower upwelling (the supply of cold water from below along the coast due to southerly winds), a phenomena that has occurred in other years in this region. The area that is warmer than normal within this coastal region (Fig. 2; the science-quality, time-delayed data used for analysis) is still below our area tracking threshold, but we will continue to monitor this area.
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that NEP2023A will continue in the offshore waters through this summer. Additionally, we note that the liklihood of El Niño developing this summer and fall has increased over the past months (see https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml) and we are currently in an “El Niño watch” status. El Niño combined with the current large offshore marine heatwave, may indicate the system is heading towards conditions similar to that encountered in 2014-2015, the last period during which we had a similar confluence of these two extremes. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Update 3-20-23
We continue to track large marine heatwave (LMH) NEP22A that formed in late January 2022 and has continued through at least March 2023. After contracting during fall 2022 (Fig. 4b) from its maximum extent in Aug (Fig. 3b), this heatwave again increased in size during late Dec/January 2023 to approximately 4 million km2. After January, this heatwave steadily decreased until about mid Feb, after which, this feature has now shown slow expansion to its current state. Unlike heatwaves of the past several years, which tend to fully disperse and fall below our tracking threshold typically during Jan-Mar, NEP22A instead has remained above these thresholds, lasting over 400 days, making it the 2rd longest and 4th largest marine heatwave in this region since 1982, when satellite monitoring data became available.
A brief summary of 2022 heatwave history: NEP22A developed on Jan 18th, 2022, when it first exceeded our LMH size threshold (>400,000 km2 in area for an individual event). By mid-February 2022, NEP22A had already reached an area of ~3 million km2 (*Note: actual sizes may be larger than reported here as we are only considering the region bounded in Figure 2 for all presented analyses). Similar to previous years, this heatwave arose in the general offshore region where the previous year’s heatwave (NEP21A) terminated, and within 30 days of the end of that previous event. Thus, it is likely that the region may have had some residual warm waters which preconditioned the region for this new heatwave development.
NEP22A remained mostly outside of the US EEZ (blue dashed line in Fig. 2) until Mid-May 2022, when there were major reversals in the typical southern pattern of winds which drive upwelling along the coast (view these winds here), most notably during May 5-19, May 22-28, and June 3-11. During these periods, NEP22A reached large portions of the central US west coast EEZ (regions 3 and 4 in Fig. 5), and up to 50% of some regions were in heatwave status during parts of May and June. After only a brief period of upwelling in late July, this heatwave or its offshoots resided fairly close to shore for most of August-October 2022 and encompassed much of the coastline, although small patches of cool water remained in various locations and times due to local upwelling (Figure 4).
The current heatwave forecast (https://psl.noaa.gov/marine-heatwaves/) suggests that NEP2022A will continue in the offshore waters through this summer. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
2022
Update 9-12-22
We continue to track the large marine heatwave NEP22A that formed in late January 2022. During late August 2022, a secondary large heatwave (NEP22B) re-merged with NEP22A (Fig. 1 and Fig 2), which now encompasses an area of roughly 7.6 million km^2, making this the 4th largest marine heatwave in this region since monitoring began in 1982. After only a brief period of upwelling in late July, these heatwaves have resided fairly close to shore for most of August and encompassed much of the coastline, although small patches of cool water remain in various locations and times due to local upwelling.
Tracking the history of these heatwaves this year, NEP22A developed on Jan 18th, 2022 when it first exceeded our size threshold (>400,000 km^2 in area). By mid-February 2022, NEP22A had already reached an area of ~3 million km^2 (*Note: actual sizes may be larger than reported here as we are only considering the region bounded in Figure 2 for all presented analyses). Similar to previous years, this heatwave arose in the general offshore region where the previous year’s heatwave (NEP21A) terminated, and within 30 days of the end of that previous event. Thus, it is likely that the region may have had some residual warm waters which preconditioned the region for this new heatwave development.
NEP22A remained mostly outside of the US EEZ (blue dashed line in Fig. 2) until mid May, 2022, when there were major reversals in the normal upwelling wind patterns here, most notably during May 5-19, May 22-28, and June 3-11. During these periods, the large offshore heatwave reached large portions of the central US west coast (regions 3 and 4 from Figure 5; up to 50% of these regions were in heatwave status during parts of May and June). These conditions are similar, but of a larger and longer scale, to what happened in 2021 when an “upwelling relaxation” event allowed the offshore heatwave to impact the coast during a week in mid-June 2021. During late June and July, NEP22A also split into two, still fairly large, but slightly separated fragments, one to the northwest (NEP22A) and one to the southeast (NEP22B). Since that time, these features have re-merged and re-split several times, likely dependent on the large-scale wind patterns bisecting this area from west to east as driven by the large-scale atmospheric pressure fields.
Besides these two large heatwaves, we have also been tracking substantial warming off the coast of southern California, within the Southern California Bight (SCB). Conditions within the SCB and to the south along the coast remain warmer than normal, and have exceeded the heatwave threshold for most of the summer. At several times since the beginning of August, warming in the SCB has been contiguous with NEP22B, although the warming began much earlier than the large-scale intrusions of either MHW into the coastal region. During the “blob” of 2014-2015, it was the eventual merging of the offshore developed heatwave to the nearshore southern California heatwave (a separate heatwave of its own), which led to the outstanding and unprecedented single giant heatwave of those years. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Update for 8-23-22
In early August 2022, a secondary large marine heatwave (NEP22B) formed after splitting from NEP22A, the primary heatwave we have been tracking since January 2022. NEP22B entered the coastal region and has remained within the US west coast EEZ since that time (Fig. 1 and Fig 2). Both NEP22B and NEP22A (discussed below), are quite large in area and contain very high sea surface temperature anomalies, up to 8°C above the normal temperatures for this time of year in some places. The recent entrance of NEP22A into the nearshore coastal region coincided with several large-scale wind relaxation events, which tend to cause either reduced coastal upwelling, or downwelling, depending on the length and strength of the relaxation. This follows a pattern, occurring as early as May 2022,of coastal intrusions by offshore heatwaves following wind relaxation events. Although MHW features now encompass much of the coastline, small patches of cool water remain in various locations due to local upwelling.
Tracking the history of these heatwaves this year, NEP22A (Fig. 2, now in the northwest of the study region), developed on Jan 18th, 2022 (Fig. 4b) when it first exceeded our size threshold (>400,000 km^2 in area). By mid-February 2022, NEP22A had already reached an area of ~3 million km^2 (*Note: actual sizes may be larger than reported here as we are only considering the region bounded in Figure 2 for all presented analyses). Similar to previous years, this heatwave arose in the general offshore region where the previous year’s heatwave (NEP21A) terminated, and within 30 days of the end of that previous event. Thus, it is likely that the region may have had some residual warm waters which preconditioned the region for this new heatwave development.
NEP22A remained mostly outside of the US EEZ (blue dashed line in Fig. 2) until mid May, 2022, when there were major reversals in the normal upwelling wind patterns (see), most notably during May 5-19, May 22-28, and June 3-11. During these periods, the large offshore heatwave reached large portions of the central US west coast (regions 3 and 4 from Figure 5; up to 50% of these regions were in heatwave status during parts of May and June). These conditions are similar, but of a larger and longer scale, to what happened in 2021 when an “upwelling relaxation” event allowed the offshore heatwave to impact the coast during a week in mid-June 2021. During late June and July, NEP22A also split into two, still fairly large, but slightly separated fragments, one to the northwest (NEP22A) and one to the southeast (NEP22B). Since that time, these features have re-merged and re-split several times, likely dependent on the large-scale wind patterns bisecting this area from west to east as driven by the large-scale atmospheric pressure fields.
Besides these two large heatwaves, we have also been tracking substantial warming off the coast of southern California, within the Southern California Bight (SCB). Conditions within the SCB and to the south along the coast remain warmer than normal, at times exceeding the heatwave threshold. At several times since the beginning of August, warming in the SCB has been contiguous with NEP22B, although the warming began much earlier than the large-scale intrusions of either MHW into the coastal region. During the “blob” of 2014-2015, it was the eventual merging of the offshore developed heatwave to the nearshore southern California heatwave (a separate heatwave of its own), which led to the outstanding and unprecedented single giant heatwave of those years. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Update for 7-25-22
We are continuing to track a large marine heatwave, NEP22A (Fig. 2), which developed on Jan 18th, 2022 (Fig. 4b) when it first exceeded our size threshold (>400,000 km^2 in area). By mid February 2022, NEP22A had already reached an area of ~3 million km^2 (*Note: actual sizes may be larger than reported here as we are only considering the region bounded in Figure 2 for all presented analyses). Similar to previous years, this heatwave arose in the general offshore region where the previous year’s heatwave (NEP21A) terminated, and within 30 days of the end of that previous event. Thus it is likely that the region may have had some residual warm waters which preconditioned the region for this new heatwave development.
NEP22A remained mostly outside of the US EEZ (blue dashed line in Fig. 2) until mid May, 2022, when there were major reversals in the normal upwelling wind patterns (see), most notably during May 5-19, May 22-28, and June 3-11. During these periods, the large offshore heatwave reached large portions of the central US west coast (regions 3 and 4 from Figure 5; up to 50% of these regions were in heatwave status during parts of May and June). These conditions are similar, but of a larger and longer scale, to what happened in 2021 when an “upwelling relaxation” event allowed the offshore heatwave to impact the coast during a week in mid-June 2021. During late June and July, NEP22A also split into two, still fairly large, but slightly separated fragments, one to the north and one to the south. Since that time, these features have re-merged and re-split several times, likely dependent on the large-scale wind patterns bisecting this area from west to east as driven by the large-scale atmospheric pressure fields. The most current raw SST anomaly (Figure 1) suggests that the northern and more offshore fragment has increased in intensity, whereas there are still considerable amounts of anomalously warm waters just offshore of the central and northern California coast.
Besides the large offshore heatwave, we have also been tracking substantial warming off the coast of southern California, within the Southern California Bight (the SCB). Conditions within the SCB and to the south along the coast remain warmer than normal, at times exceeding the heatwave threshold. During the “blob” of 2014-2015, it was the eventual joining of the offshore developed heatwave to the nearshore southern California heatwave (a separate heatwave of its own), which led to the outstanding and unprecedented single giant heatwave of those years. We will continue to monitor and report on the status of these heatwaves as they develop.
Update for 6-14-22
We are continuing to track a large marine heatwave, NEP22A (Fig. 2), which developed on Jan 18th, 2022 (Fig. 4b) when it first exceeded our size threshold (>400,000 km^2 in area). By mid February 2022, NEP22A had already reached an area of ~3 million km^2, which is close to its current size, within our analyzed region of the eastern North Pacific. Similar to previous years, this heatwave arose in the general offshore region where the previous year’s heatwave (NEP21A) terminated, and within 30 days of the end of that previous event. Thus it is likely that the region may have had some residual warm waters which preconditioned the region for this new heatwave development.
The most recent raw SST anomaly plot (Fig. 1) suggests NEP22A has reached the US west coast. During May 5-19, May 22-28, and most recently June 3-11, there were major reversals in the typical southerly pattern of upwelling winds along the coast , which likely allowed the formerly offshore heatwave to reach the coast (for a view of these winds, (see). These conditions are similar, but of a larger and longer scale, to what happened in 2021 when an “upwelling relaxation” event allowed the offshore heatwave to impact the coast during a week in mid-June 2021. NEP21A did not return to the coast, as upwelling winds remained fairly strong and consistent for the rest of the summer. Whether strong upwelling will re-commence and reduce the impacts of this 2022 heatwave on the coast are unknown at this time.
What is also different this year compared to previous years is that the heatwave this year developed nearly two months earlier than the last three years’ events, thus setting the stage for a potentially even larger event this year. Conditions could easily be modified by less-predictable atmospheric changes, which are beyond the scope of the analysis here. Besides the large offshore heatwave, we have also been tracking substantial warming off the coast of southern California, within the Southern California Bight. During the “blob” of 2014-2015, it was the eventual joining of the offshore developed heatwave to the nearshore southern California heatwave (a separate heatwave of its own), which led to the outstanding and unprecedented single giant heatwave of those years. We will continue to monitor and report on the status of these heatwaves as they develop.
2021
Blob Narrative Update 6/4/21
Marine heatwave NEP20b, which began in May 2020 and reached a maximum size of ~9.1 million km2 in late September 2020, steadily decreased in size during the winter and spring, continued a displacement further offshore, and fell below the area threshold (400,000 km^2) for classification as a large marine heatwave on April 4th, 2021 (Fig 4b). At its maximum size, NEP20b was the 2nd largest MHW (by a slight margin) seen in this region since satellite monitoring and analysis began in 1982 (Fig. 4). It is also now one of the longest lasting MHWs on record, having lasted 309 days. An animation of marine heatwave development during 2020 can be viewed here.
In late April 2021, another large heatwave (NEP21A) began to form (Fig. 2), in the same region near where NEP20b declined. As of June 4th, this new heatwave (NEP21A) had reached an area of approximately 2,400,000 km^2 (Fig 2, 4b), nearly tripling in area over the past three weeks, and advancing ~100km closer to the US west coast (now at approximately 800km offshore). Given its distance from shore, the majority of the US west coast EEZ (blue dashed outline, Fig. 2, 5) currently has no waters in heatwave status (with the exception of a small region of warm water within the southern California bight), however, the most recent SST anomaly plots, at the time of the writing of this update, indicate that 2021A is continuing to expand (Fig.1). We continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impactsBlob Narrative Update 5/21/21
Marine heatwave NEP20b, which began in May 2020 and reached a maximum size of ~9.1 million km2 in late September 2020, steadily decreased in size during the winter and spring, continued moving further offshore, and fell below the area threshold (400,000 km^2) for classification as a large marine heatwave on April 4th, 2021 (Fig 4b). At its maximum size, NEP20b was the 2nd largest MHW (by a very slight margin) seen in this region since satellite monitoring and analysis began in 1982 (Fig. 4). It is also now one of the longest lasting heatwaves on record, having lasted 309 days. An animation of marine heatwave development during 2020 can be viewed here.
Marine heatwave NEP20b, which began in May 2020 and reached a maximum size of ~9.1 million km2 in late September 2020, steadily decreased in size during the winter and spring, continued moving further offshore, and fell below the area threshold (400,000 km^2) for classification as a large marine heatwave on April 4th, 2021 (Fig 4b). At its maximum size, NEP20b was the 2nd largest MHW (by a very slight margin) seen in this region since satellite monitoring and analysis began in 1982 (Fig. 4). It is also now one of the longest lasting heatwaves on record, having lasted 309 days.
Blob Narrative Update 4/14/21
Heatwave NEP20b, which began in May 2020, and reached a maximum size of ~9.1 million km^2 in late September 2020, has steadily decreased in area during the winter and spring (now at ~800,000 km^2 in area) and continued moving further offshore (Fig. 2). Given its distance from shore, the majority of the US west coast EEZ (blue dashed outline in figures) currently has no waters in heatwave status (Fig. 5). At its maximum size, NEP20b was the 2nd largest MHW (by a very slight margin) seen in this region since satellite monitoring and analysis began in 1982 (Fig. 4). It is also now one of the longest lasting heatwaves, at 304 days, as of March 29, 2021.
NEP20b directly followed NEP20a (which in turn directly followed NEP19, a very large marine heatwave that lasted from mid 2019 to Feb 2020), and was mainly centered in the northwest of the study region with temperatures exceeding 2 standard deviations above normal. NEP20a reached a maximum size of ~4 million km^2 on April 26, 2020, making it the 9th largest MHW over the past 38 years (Fig. 4). After April, however, NEP20a lost strength and eventually split into smaller fragments. NEP20b arose from one of these fragments in early June, growing steadily and re-encompassing the area once occupied by NEP20a by early August, 2020. NEP20b then receded to further offshore during Nov and Dec. This recession is similar to that seen with NEP19 during October and November, 2019; however, the 2020 recession of the heatwave is approximately 1 month later than in 2019. An animation of marine heatwave development during 2020 can be viewed here
Blob Narrative Update 2/10/21
Heatwave NEP20b, which reached a maximum size of ~9.1 million km^2 in late September 2020, has steadily decreased in area over the past two months (now at ~700,000 km^2 in area) and moved further offshore (Fig. 1). Given its distance from shore, the majority of the US west coast EEZ (blue dashed outline in figures) currently has no waters in heatwave status (Fig. 5). At its maximum size, NEP20b was the 2nd largest MHW (by a very slight margin) seen in this region since satellite monitoring and analysis began in 1982 (Fig. 4).
NEP20b directly followed NEP20a, which was mainly centered in the northwest of the study region and had temperatures exceeding 2.0 SD above normal. NEP20a reached a maximum size of ~4 million km^2 on April 26, 2020, making it the 9th largest MHW over the past 38 years (Fig. 5). After April, however, NEP20a lost strength and eventually split into smaller fragments. NEP20b arose from one of these fragments in early June, growing steadily and re-encompassing the area once occupied by NEP20a (which in turn, followed NEP19, see above) by early August, 2020. As discussed below, NEP20b then receded to further offshore during Nov and Dec. This recession is similar to that seen with NEP19 during October and November, 2019; however, this year’s recession of the heatwave is approximately 1 month later than in 2019. An animation of marine heatwave development during 2020 can be viewed here.
The smaller yet intensely warm area we had been tracking within the Southern California Bight has now completely dissipated, with waters off southern California returning to near normal temperatures for this time of year (Fig. 1) and leaving mostly cool or climatological water temperatures in this region. We continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
2020
Blob Narrative Update 9/20/20
We continue tracking heatwave NEP20b, which has gained size over the past two weeks to become the largest heatwave by area (~9.8 million km2) since monitoring began in 1982 (Fig. 1). This feature split apart into a far offshore component and a nearshore component around Aug. 9, 2020; however, these two parts reconnected in late August, and then extending further south, bringing it to its current size. This heatwave follows NEP20a, which was mainly centered to the northwest with temperatures exceeding 2.0 SD above normal around Apr 26, 2020. NEP20a reached a maximum size of ~4 million km2, making it the 9th largest MHW over the past 38 years (Fig. 5). Since April, however, NEP20a lost strength, and eventually split into smaller fragments. NEP20b arose from one of these fragments in early June, growing steadily and re-encompassing the area once occupied by NEP20a (which in turn followed on NEP19, see below) by around August 1, 2020. NEP20b appears to be held at bay by relatively strong coastal upwelling, as seen by the negative SST anomalies (blue in Fig. 1) in these regions. An animation of marine heatwave development during 2020 can be viewed here: https://youtu.be/EjH1miyY1I8
The smaller yet intensely warm area we we continue track within the southern California Bight has varied in size and strength over the past few months, but has generally grown in size (Fig. 1). Although this area has been anomalously warm for several months, it remains under our size-based threshold for declaration of an independent MHW. If this region were to connect with NEP20b to the north, as occurred during the 2014 event, the area of this feature would further increase the size of NEP20b. We continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
The Northeast Pacific Marine Heatwave of 2019, also known as NEP19, decreased below our heat wave classification thresholds and ended in terms of its surface expression on January 17, 2020. NEP19 lasted 239 days and covered approximately 8.5 million km2 at its peak (Fig. 4, 5; archived images can be found here), officially becoming the second largest and longest event recorded in the northern Pacific Ocean since 1982, when satellite-based remote sensing of sea surface temperatures began in a consistent fashion.
Blob Narrative Update 9/9/20
We continue tracking heatwave NEP20b, which has gained size over the past three weeks to become the 3rd largest heatwave by area (~6.5 million km2) since monitoring began in 1982 (Fig. 1). This feature split apart into a far offshore component and a nearshore component around Aug. 9th; however, these two parts reconnected in late August, bringing it to its current size. This heatwave follows NEP20a, which was mainly centered to the northwest with temperatures exceeding 2.0 SD above normal around Apr 26th. NEP20a reached a maximum size of ~4 million km2, making it the 9th largest MHW over the past 38 years (Fig. 5). Since April, however, NEP20a lost strength, and eventually split into smaller fragments. NEP20b arose from one of these fragments in early June, growing steadily and re-encompassing the area once occupied by NEP20a (which in turn followed on NEP19, see below) by around August 1, 2020. NEP20b appears to be held at bay by relatively strong coastal upwelling, as seen by the negative SST anomalies (blue in Fig. 1) in these regions. An animation of marine heatwave development during 2020 can be viewed here: https://youtu.be/EjH1miyY1I8
The smaller yet intensely warm area we we continue track within the southern California Bight has varied in size and strength over the last few weeks, but has generally grown over the past two months (Fig. 1). Although this area was anomalously warm for several months, it remains under our size-based threshold for declaration of an independent MHW. If this region were to connect with NEP20b to the north, as occurred during the 2014 event, the area of this feature could eventually rival that of the largest heatwave on record. We continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
The Northeast Pacific Marine Heatwave of 2019, also known as NEP19, decreased below our heat wave classification thresholds and ended in terms of its surface expression on January 17, 2020. NEP19 lasted 239 days and covered approximately 8.5 million km2 at its peak (Fig. 4, 5; archived images can be found here), officially becoming the second largest and longest event recorded in the northern Pacific Ocean since 1982, when satellite-based remote sensing of sea surface temperatures began in a consistent fashion.
Blob Narrative Update 6/23/20
After the decline of NEP19 in January 2020 (see below), a fairly large pool of anomalously warm water remained in that same location. Temperatures in this offshore pool of water again surpassed our marine heatwave threshold on Feb19, and have remained above threshold through this current posting (Fig. 1,2,5). This new heatwave, NEP20, reached a size of ~4 million km^2 with intensities in excess of 2 STDEVs above normal (Fig. 5.) around Apr 26th. That maximum size places it within the top 10 largest MHWs that have occurred over the past 38 years. Since April, however, this heatwave has lost some strength, eventually splitting into a few smaller pieces. Although the main core to the NW remains a fairly strong heatwave, in general terms, its far offshore location suggests this heatwave will have few impacts on our coastal ecosystems.
However, the leftover remnants of NEP20 (discussed above) have formed as smaller, secondary warm-water features off the coasts of southern California and northern California / Oregon. Though extremely warm, neither feature has yet reached our size-based threshold for declaration of independent MHWs. We continue to monitor the area, duration, and coastal proximity of surface water temperatures for these features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Additionally, there was a smaller, secondary feature which formed off the coast of southern CA. This fairly warm feature, however, only reached a size of ~150,000 km2, and thus has not quite reached our size-based threshold for declaration of a MHW. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these two features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
Currently, there is another fairly large patch of anomalously warm water located off the coast of northern California and Oregon. This patch of warm water is actually a leftover remnant of the southeastern-most extent of the earlier heatwave centered to the NW region (discussed above) from before that feature was broken up into several smaller patches.
The Northeast Pacific Marine Heatwave of 2019, also known as NEP19, decreased below our heat wave classification thresholds and ended in terms of its surface expression on January 17, 2020. NEP19 lasted 239 days and covered approximately 8.5 million km2 at its peak (Fig. 4, 5; archived images can be found here), officially becoming the second largest and longest event recorded in the northern Pacific Ocean since 1982, when satellite-based remote sensing of sea surface temperatures began in a consistent fashion.
Blob Narrative Update 4/29/20
After the decline of NEP19 in January 2020 (see below), a fairly large pool of anomalously warm water has remained in the far offshore region of our analysis domain. Temperatures in this offshore pool of water surpassed our marine heatwave threshold briefly, from February 21-March 7, 2020, and again from March 14, 2020 continuing through the current posting (Fig. 1,2,5). This new heatwave, NEP20, has now reached a size of ~4 million km^2 with intensities in excess of 2 STDEVs above normal (Fig. 5.). Its current size now places it within the top 10 largest MHWs that have occurred over the past 38 years. Additionally, there is now a smaller, secondary feature which has formed off the coast of southern CA. This fairly warm feature, however, has only reached a size of ~150,000 km2, and thus has not quite reached our size-based threshold for declaration of a MHW. We will continue to monitor the area, duration, and coastal proximity of surface water temperatures for these two features in the northeast Pacific and communicate with other researchers and policy-makers to understand the array of possible west coast impacts.
The Northeast Pacific Marine Heatwave of 2019, also known as NEP19, decreased below our heat wave classification thresholds and ended in terms of its surface expression on January 17, 2020. NEP19 lasted 239 days and covered approximately 8.5 million km2 at its peak (Fig. 4, 5; archived images can be found here), officially becoming the second largest and longest event recorded in the northern Pacific Ocean since 1982, when satellite-based remote sensing of sea surface temperatures began in a consistent fashion.
2019
Blob Narrative Update 11/5/19
We continue to track the marine heatwave known as the Northeast Pacific Marine Heatwave of 2019, or NEP19. In early October, we observed the heatwave split into two distinct features. Our latest images (Fig. 1,2) show the marine heatwave has reformed into a single, yet smaller, feature (as compared to its maximum size in August 2019) and has moved farther offshore. We see surface temperatures have cooled across much of the nearshore areas for the entire US west coast; southern OR and northern CA are currently experiencing colder than average temperatures (Fig. 1).
Even with this decrease in size and intensity, the current marine heatwave, which formed in May 2019, is still among the most significant events seen in the northern Pacific Ocean during the last 40 years (Fig. 4,5), with continued sea surface temperatures as much as 3°C above average. Like the blob, NEP19 formed as changes in atmospheric conditions dampened the winds that otherwise mix and cool the ocean’s surface. Unlike the blob of 2014-15, which remained near the coast during the fall and winter during 2014, the current MHW has retreated to a location much further offshore.
Conditions will become increasingly dynamic as fall and winter storms begin forming in the Northeast Pacific. We continue to monitor the area, duration, and coastal proximity of this marine heatwave and coordinate with other researchers and policy-makers to understand the array of possible west coast impacts.