donsutherland1

Because the empirical evidence is strong. It assumes basic understanding that statistics measure things. Statistics are not abstractions unto themselves. The changes taking place are leading to warmer, drier conditions in general. The incidence of extreme heat, including this August’s record-breaking heat in parts of California and Arizona have increased the frequency of conditions that are conducive for wildfires.

You misunderstand the differences of climate (fixed point in time) and climate change (delta between two states of the climate) and the role that measurements play in providing insight into both. An analogy is useful: Average heart rate is a statistic. Average heart rate has no power over one’s health and has never caused one a heart attack or other serious heart issue. The underlying assumption, if one applies the implicit arguments concerning climate change to this measure, would be that whether one’s heart rate is rapidly slowing or becoming highly irregular would be irrelevant. In other words, there’s nothing to see. That would be dangerously naive. Large and dramatic changes could well indicate that a person is suffering a heart issue which, if not addressed, could pose a mortal threat. The same holds true for climate statistics. The change over time has meaning. And, because there is a relationship between many of the climate variables (higher temperatures-incidence of extreme heat, changes in global distribution of temperatures and the jet stream, greater warmth-greater capacity of the atmosphere to hold moisture, etc.) the overall changes taking place pose risks ranging from heat waves, drought, rising sea levels, etc. None of these changes are trivial.

If the idea that Phoenix’s climate will resemble that of Baghdad is reasonably accurate, then there could be some nights with lows at or above 100 (Phoenix’s lows are higher than those in Baghdad) and highs in the lower and middle 120s during periods of extreme heat.

New York City's Central Park finished with a monthly mean temperature of 76.9° for August. Its summer mean temperature was also 76.9°, which tied summers 1949, 1983, and 1993 for the fourth warmest summer on record. Tomorrow will be mainly cloudy with showers and some periods of rain possible. Rainfall amounts will likely come to 0.25" or less for much of the region. Temperatures will be in the middle and upper 70s. Beyond midweek, temperatures will likely return to above normal levels. Afterward, a deep trough in Canada will move toward the Great Lakes Region and provide a period of cooler weather. Most of the colder air will stay west of the Appalachians. That trough may persist until near or just after mid-September. Nevertheless, the first half of September will likely wind up somewhat warmer than normal and September, as a whole, will likely finish warmer than normal (generally 1°-3° above normal). Parts of the Northeast and also Southwest recorded their warmest summer on record. At New York City's LaGuardia Airport, the summer mean temperature was 79.5°, which surpassed the prior record of 79.2° from 2010. Phoenix had, by far, its warmest summer on record. Phoenix concluded with a summer mean temperature of 96.7°. That smashed the previous record of 95.1°, which was set in summer 2013 and tied in summer 2015. August 2020 was surpassed July's record for the warmest month on record with a mean temperature of 99.0°. To date, Phoenix has smashed its record for most days with high temperatures of 110° or above (50), 115° or above (13), and low temperatures of 90° or above (28). More on Phoenix's historic summer can be found here: The ENSO Region 1+2 anomaly was -0.6°C and the Region 3.4 anomaly was -0.7°C for the week centered around August 26. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.02°C and the ENSO Region 3.4 anomaly has averaged -0.63°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall. The SOI was +21.36. Today, the preliminary Arctic Oscillation (AO) figure was -0.535. Daily MJO data remains unavailable. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Finally, on August 30, Arctic sea ice extent was 3.995 million square kilometers (JAXA). 2020 will be the second consecutive year with a minimum figure below 4.000 million square kilometers and third time on record. The highest 25% bound is 3.768 million square kilometers. The lowest 25% bound is 3.589 million square kilometers.

Phoenix concluded, by far, its hottest summer on record. During June-August 2020, Phoenix had a mean temperature of 96.7°. That smashed the old record of 95.1°, which was set in 2013 and tied in 2015. Table 1: Summer 2020 Average Temperatures Since 2009, every summer has ranked among the 20 warmest summers on record. In addition, 2015, 2016, 2019 and 2020 have ranked among the 10 warmest summers. Table 2: 20 Warmest Summers Monthly Mean Temperatures: June: 92.0° (21st warmest June on record) July: 98.9° (warmest July on record; old record: 98.3°, 2009) August: 99.1° (warmest August on record; old record: 98.3°, 2011) July 2020 set a new monthly mean temperature. August 2020 surpassed that record. Just 3 (15%) of the 20 warmest months were recorded prior to 2000. 17 (85%) of the warmest months occurred 2000 or later and 10 (50%) of the warmest months occurred 2010 or later. There were three cases where both July and August ranked among the 20 warmest months: 2007, 2019 and 2020. Table 3: 20 Warmest Months Table 4: Record High Minimum Temperatures Table 5: Record High Maximum Temperatures Select Monthly Heat Thresholds: Highs 110° or above: 22 days, August 2020 (old record: 19 days, July 2020; prior old record: 18 days, June 1974) Highs 115° or above: 7 days, August 2020 (tied record set in June 1974) Lows: 90° or above: 16 days, July 2020 (old record: 11 days, July 2006); August 2020 had 12 such days. Select Summer Heat Thresholds: Highs 110° or above: 48 days (old record: 31 days, 2007 and 2011) Highs 115° or above: 13 days (old record: 7 days, 1974) Lows: 90° or above: 28 days (old record: 15 days, 2003 and 2013) Climate Change: Anthropogenic climate change is driving a warming of Phoenix's summers. The warming has accelerated in recent decades. The observed global warming since the 1950s is unequivocal with anthropogenic greenhouse gas emissions being the dominant driver of that warming (IPCC Climate Change Synthesis Report 2014). The warming is a global phenomenon with 98% of the world having experienced its warmest 51 years during the current 2,000 years (Neukom, et al. 2019). Recent research suggests that Phoenix's climate will resemble that of Baghdad by 2050 (Bastin, et al. 2019). During the summer, Baghdad typically receives no rainfall. Baghdad's average high temperatures (Weather Atlas 2002-2020) during the summer months are: June: 105.8° July: 111.2° August: 109.4° Summer Average High Temperature: 108.8° Until summer 2020, the highest mean summer maximum temperature was 107.0°, which was set in 1978 and tied in 1989. The highest monthly summer maximum temperature was 109.8°, which was set in July 1989 and tied in July 2020. August 2020 surpassed that record with an average high temperature of 110.7°. As recently as 2000, Phoenix's average low temperature during the summer was 79.8°. Since 1999, Phoenix has had no summer with an average low temperature below 80.0°. Prior to 2020, the highest average monthly minimum temperature was 87.5°, which was set in August 2011. July 2020 had an average minimum temperature of 88.0°. Based on the above research findings, summer 2020 provides a glimpse of what a typical Phoenix summer will be like by 2050. Table 6: Average Summer Temperatures (30-Year Moving Average) Climate change is also resulting in an increase in the frequency of days on which the low temperature stays at or above 90° and the high temperature reaches 100° or above, 110° or above, and 115° or above. Table 7: Average Annual Days at Set Thresholds (30-Year Moving Average) According to the Fourth National Climate Assessment, Phoenix saw 60 to nearly 100 100° days per year at the 5th and 95th percentiles. Under the RCP 4.5 scenario, those figures are projected to increase to 110-141 days per year during the 2070-2099 period. During the 1950-1999 period, 9 (18%) of years saw the number of 100° days fall within the projected RCP 4.5 interval (U.S. Global Change Research Program, 2017). From 2000-2019, 11 (55%) of years fell within that interval. 2020 is all but certain to become the 12th case since 2000 to meet that higher interval. Moreover, through August 31, the 30-year moving average is just above 110 days per year. During the summer, 48 days saw high temperatures 110° or above. The previous summer record was 31 days, which was set in 2007 and tied in 2011. During 2020, there have been 50 such days vs. the prior record of 33 days, which was set in 2011. There were also 28 days on which the minimum temperature was 90° or above, which eclipsed the previous record of 15, which was set in 2003 and tied in 2013. In addition, the number of very hot (high temperature of 110° or above) and super hot (high temperature of 115° or above) days has been increasing as a share of the increasing number of 100° days. For the 30-year period ending in 1980, 12.6% of 100° days had high temperatures of 110° or above and 1.0% saw temperatures reach 115° or above. For the 30-year period ending in 2000, those figures increased to 15.7% and 1.7% respectively. For the period ending in 2020 (through August 31), those figures increased further to 18.8% and 2.0% respectively. Overall, the frequency and intensity of compound summertime hot extremes (events that combine daytime and nighttime heat where such temperatures are above their 90th percentile for their calendar) has been increasing especially in geographic locations that include the U.S. Southwest (Wang 2020). The increase in forcing associated with anthropogenic greenhouse gases is the dominant driver of this outcome. (Wang 2020). During summer 2020, 15 record high minimum temperatures were tied or broken in Phoenix and 14 record high maximum temperatures were tied or broken. On 7 days, both record high minimum and maximum temperatures were tied or broken. Summary: Summer 2020 saw Phoenix record its highest summer temperature on record. It also saw Phoenix experience its two hottest months on record. In addition, Phoenix easily surpassed records for the most days on which the temperature reached 110° or above and on which minimum temperature was 90° or higher. Anthropogenic climate change, which has turned hot patterns hotter and increased pattern persistence, is largely responsible for this exceptional warmth. Based on the latest research, the extreme heat of summer 2020 will likely become the "new normal" by 2050. Updates: September 1-7: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5650331 Summer High Temperatures: Climate Model Projections and Actual Outcomes: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5661632 Phoenix Records a 90° Mean Temperature for September: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5664607 Phoenix Experiences its Hottest Week in October: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5668129 Phoenix Sets New Annual Record for 100° Days: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5672012 A Very Warm October Concludes in Phoenix: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5684211 Phoenix Experiences its Warmest 5-Day November Period on Record: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5687553 Phoenix Experiences Latest 90° Days on Record: https://www.americanwx.com/bb/topic/53697-phoenix-records-its-hottest-summer-on-record/?do=findComment&comment=5698629

A healthier diet and other lifestyle changes, independent of anything to do with climate change, would likely reduce comorbidities among the American population, expanding with life spans and the quality of life.

September Preview: In the New York City area, September has increasingly become an extension of summer. Prior to 2000, a monthly mean temperature of 70° or above was relatively uncommon. Prior to 1950, Central Park saw such warmth about once every 5.4 years. From 1950-1999 (during which New York City has had a mature urban footprint), such warmth was recorded approximately once every 4.5 years. Since 2000, 70° Septembers have occurred about once every 2.0 years. There have been 10 such Septembers during the 2000-2019 period, which is just below the figure of 11 recorded during 1950-1999. Since 2010, New York City has had 7 cases where September had a mean temperature of 70° or above, including the last four years. During the last 30 years, September has had a mean temperature of 69.0°, which is the warmest 30-year period on record for September. During the last 10 years, September has had a mean temperature of 70.5°, which is the warmest 10-year period on record for that month. Records go back to 1869. The 1981-2010 normal temperature for September is 68.0°. New York City's 30-Year Moving Averages for September: 30-Year Period ending: 1990: 68.1° 2000: 68.1° 2010: 68.4° 2019: 69.0° September 2020: Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. The first half of September will likely see a deep trough located over the Great Lakes to Central Canada. However, the Western Atlantic Ridge could blunt the amount of cool air that reaches the New York City area. Afterward, that trough could dissipate. Overall, September will likely wind up with a mean temperature near 70° or about 2° above normal in New York City.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.8 2.0 1.7 0.0 1.0 0.3 0.2 2.7 3.2

Morning thoughts... Temperatures started out mainly in the 50s outside the major cities and lower 60s in such cities as New York, Newark, and Philadelphia. August will end on a cool note under variably cloudy skies. There will be more clouds around than yesterday. Temperatures will reach the middle and upper 70s in the region. Likely high temperatures around the region include: New York City (Central Park): 76° Newark: 77° Philadelphia: 78° Temperatures will likely return to above normal levels near or just after mid-week. Afterward, a deep trough in Canada will move toward the Great Lakes Region and provide a period of cooler weather. That trough may persist until near mid-September. 2020 is the record 7th consecutive year that Central Park has had no August temperatures below 60°. The previous record was 3 consecutive years during 1931-33, 1995-97, and 2001-03. The last time the mercury fell below 60° was August 15, 2013 when the temperature fell to 59°. LaGuardia Airport will conclude its warmest summer on record with a mean temperature near 79.5°. The existing record is 79.2°, which was set in 2010.

Arctic sea ice extent fell to 3.995 million square kilometers on JAXA. That makes 2020 the second consecutive year that will have a minimum extent below 4.000 million square kilometers and the third such year on record.

I suspect the problem with the “Green New Deal” has less to do with its climate provisions than with the non-climate provisions. Hopefully, sooner rather than later, science will take precedence over other interests when it comes to addressing the challenge of climate change.

The averages were boosted more by near record and record periods of abnormally high minimum temperatures.

It is. The IPCC is considering increasing the confidence figure for anthropogenic factors being the dominant cause of the ongoing warming to 99%-100% from 95%. The evidence is all but unequivocal now. I agree concerning future generations. That they will bear the highest costs from inaction, they will likely point to that inaction as being among the greatest failures in human history. They won’t be wrong. Moreover, I suspect that when Generation Z attains political leadership, they will make drastic changes (e.g., net carbon neutrality in a decade or less) to address the problem if little has been done. Inaction is squandering the time available for a transition.

Today was a picture perfect late August Day. Bright sunshine, deep blue skies, puffy cumulus clouds, low humidity and an active breeze made for an exceptional day as temperatures topped out in the upper 70s and lower 80s across the region. Tomorrow will see more in the way of clouds than today, but it should still be partly sunny. August will end on a cool note as the temperature remains below 80° in a large part of the region. Beyond midweek, temperatures will likely return to above normal levels. Afterward, a deep trough in Canada will move toward the Great Lakes Region and provide a period of cooler weather. That trough may persist until near mid-September. Nevertheless, the first half of September will likely wind up somewhat warmer than normal and September, as a whole, will likely finish at least somewhat warmer than normal. Phoenix has an implied near 100% probability of having its warmest summer on record. Phoenix will likely finish with a summer mean temperature near 96.8°. The existing record is 95.1°, which was set in summer 2013 and tied in summer 2015. July 2020 was Phoenix's warmest month on record with a mean temperature of 98.9°. August 2020 will likely exceed that figure. There is currently an implied 87% probability that August will exceed July's monthly record. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.8°C for the week centered around August 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.17°C and the ENSO Region 3.4 anomaly has averaged -0.55°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall. The SOI was +22.70. Today, the preliminary Arctic Oscillation (AO) figure was -1.410. On August 29, daily MJO data was unavailable. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal August. August will likely finish with a mean temperature near 76.9°. Summer 2020 will likely finish with a mean temperature near 76.9°, which would tie 2020 as Central Park's 4th warmest summer with 1949, 1983, and 1993. At LaGuardia Airport, summer 2020 will likely finish with a mean temperature of 79.5°. That would surpass the existing summer record of 79.2°, which was set in 2010. Finally, on August 28, Arctic sea ice extent was 4.059 million square kilometers (JAXA). There is an implied 98% probability that Arctic sea ice extent will reach a minimum figure below 4.000 million square kilometers for the second consecutive year and third time on record. The highest 25% bound is 3.806 million square kilometers. The lowest 25% bound is 3.604 million square kilometers.

Under partly sunny skies, the temperature rose into the upper 70s to near 80° this afternoon. Three photos from the New York Botanical Garden from this afternoon:

This year one is seeing an IOD- pattern. Last year one saw among the strongest IOD+ patterns.

Morning thoughts... Today will feature abundant sunshine with temperatures in the middle and upper 70s to perhaps around 80° in the region. Likely high temperatures around the region include: New York City (Central Park): 78; Newark: 80; and, Philadelphia: 80. August will likely end on a cool note with readings several degrees cooler than those of today. Temperatures will likely return to above normal levels near or just after mid-week. Afterward, a deep trough in Canada will move toward the Great Lakes Region and provide a period of cooler weather. That trough may persist until near mid-September. LaGuardia Airport remains on course to record its warmest summer on record. Arctic sea ice extent will likely fall below 4 million square kilometers over the next day or two for the second consecutive year and third time on record.

Tomorrow will feature abundant sunshine with temperatures in the middle and upper 70s to perhaps around 80° in the region. August will likely end on a cool note before temperatures again return to above normal levels during the first week of September. The current predominantly warmer than normal pattern will likely persist through much of September, providing a warm start to fall throughout the region. Occasional short-lived cool shots remain possible. However, uncertainty about the possibility of more sustained cool shots has increased in recent days. Phoenix has an implied near 100% probability of having its warmest summer on record. Phoenix will likely finish with a summer mean temperature near 96.8°. The existing record is 95.1°, which was set in summer 2013 and tied in summer 2015. July 2020 was Phoenix's warmest month on record with a mean temperature of 98.9°. August 2020 could approach or exceed that figure. There is currently an implied 68% probability that August will exceed July's monthly record. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.8°C for the week centered around August 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.17°C and the ENSO Region 3.4 anomaly has averaged -0.55°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall. The SOI was +18.63. Today, the preliminary Arctic Oscillation (AO) figure was -1.838. On August 28, daily MJO data was unavailable. Last year, the MJO went through a very strong passage through Phase 1 during the closing days of May. About four weeks later, a warmer than normal pattern locked in and predominated through early autumn. This year, the MJO was in Phase 1 for 3 consecutive days with an amplitude of 1.500 or above during the June 1-3 period. Last year, the SOI fell to -42.04 on June 22 when the MJO was in Phase 6. This year, the SOI plunged below -46.68 on June 5, its lowest level in more than three years. The dramatic plunge in the SOI could be the proverbial spark that kicks off a sequence of events leading to the development of a sustained warmer than normal period. The cases that saw both the MJO and SOI thresholds satisfied generally saw 10-20 days where the temperature reached or exceeded 90° in New York City during the July 1-August 31 period. New York City has had 18 days on which the temperature reached 90° or above during July-August 2020. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal August. August will likely finish with a mean temperature near 76.8°. Summer 2020 will likely finish with a mean temperature near 76.9°, which would tie 2020 as Central Park's 4th warmest summer with 1949, 1983, and 1993. At LaGuardia Airport, summer 2020 will likely finish with a mean temperature of 79.5°. That would surpass the existing summer record of 79.2°, which was set in 2010. Finally, on August 28, Arctic sea ice extent was 4.119 million square kilometers (JAXA). There is an implied 95% probability that Arctic sea ice extent will reach a minimum figure below 4.000 million square kilometers for the second consecutive year and third time on record. The highest 25% bound is 3.843 million square kilometers. The lowest 25% bound is 3.624 million square kilometers.

Clouds broke for sunshine this afternoon, the temperature rose above 80°, and a brisk breeze blew across the waters of the Long Island Sound.

Afternoon thoughts... As of 2 pm, rainfall totals were as follows: Atlantic City: 0.23” Islip: 0.23” New York City: 0.01” Newark: None Philadelphia: 0.10” White Plains: 0.10” An area of showers and thundershowers was moving mainly eastward across southeastern Pennsylvania with a few widely scattered showers elsewhere in Pennsylvania. Overall prospects for rainfall in the New York City area have decreased. In general, New York City, Newark, and nearby suburbs will see 0.25” rain or less. Exceptions would be areas where thundershowers develop. Parts of Long Island could still pick up 0.50” or more. Western parts of the region could see the clouds begin to break early this evening.

Thank you for the tip. I appreciate it.

Wilmington DE picked up 1.03” rain in the past hour, but that area of intense rainfall is heading east-northeastward and will stay well south of Newark.

Morning thoughts... At 8:55 am, a batch of showers and thundershowers had moved into southwestern Connecticut. The area of rain was pushing northeastward. Additional showers and thundershowers are likely as the remnants of Laura approach the area. Laura will likely exit off the Delmarva Peninsula tonight. The New York City area and adjacent suburbs could pick up 0.25"-0.75" rain. A few locations on Long Island could see some locally higher amounts as Laura begins to tap into Atlantic moisture. August will end with cooler than normal temperatures, but the mercury will rebound early next week. A flash flood watch will go into effect in Phoenix this afternoon and run through tomorrow. The extreme heat that has dominated much of July and August there will relax. A warmup is likely next week there.

Laura will likely exit off the Delmarva Peninsula late tomorrow night. The system has the potential to bring an area of 1"-3" rain with locally higher amounts across parts of Virginia and the Delmarva Peninsula, along with another area with pockets of moderate to perhaps heavy rain along a frontal boundary to its north. The New York City area and adjacent suburbs could pick up 0.25"-0.75" rain. August will likely end on a cool note before temperatures again return to above normal levels during the first week of September. The current predominantly warmer than normal pattern will likely persist through much of September, providing a warm start to fall throughout the region. Occasional short-lived cool shots remain possible. Parts of the West continued to experience near record and record high temperatures. Select high temperatures included: Death Valley: 115°, Kingman, AZ: 105° Lake Havasu City, AZ: 113° Las Vegas: 106° Needles, CA: 115° Palm Springs, CA: 116° Phoenix: 112° Tucson: 107° (tied record set in 1998) Yuma, AZ: 113° Phoenix has an implied near 100% probability of having its warmest summer on record. Phoenix will likely finish with a summer mean temperature near 96.8°. The existing record is 95.1°, which was set in summer 2013 and tied in summer 2015. July 2020 was Phoenix's warmest month on record with a mean temperature of 98.9°. August 2020 could approach or exceed that figure. There is currently an implied 60% probability that August will exceed July's monthly record. The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.8°C for the week centered around August 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.17°C and the ENSO Region 3.4 anomaly has averaged -0.55°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall. The SOI was +9.65. Today, the preliminary Arctic Oscillation (AO) figure was -1.512. On August 27, daily MJO data was unavailable. Last year, the MJO went through a very strong passage through Phase 1 during the closing days of May. About four weeks later, a warmer than normal pattern locked in and predominated through early autumn. This year, the MJO was in Phase 1 for 3 consecutive days with an amplitude of 1.500 or above during the June 1-3 period. Last year, the SOI fell to -42.04 on June 22 when the MJO was in Phase 6. This year, the SOI plunged below -46.68 on June 5, its lowest level in more than three years. The dramatic plunge in the SOI could be the proverbial spark that kicks off a sequence of events leading to the development of a sustained warmer than normal period. The cases that saw both the MJO and SOI thresholds satisfied generally saw 10-20 days where the temperature reached or exceeded 90° in New York City during the July 1-August 31 period. New York City has had 18 days on which the temperature reached 90° or above during July-August 2020. Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal August. August will likely finish with a mean temperature near 76.9°. Summer 2020 will likely finish with a mean temperature near 76.9°, which would tie 2020 as Central Park's 4th warmest summer with 1949, 1983, and 1993. At LaGuardia Airport, summer 2020 will likely finish with a mean temperature of 79.4°. That would surpass the existing summer record of 79.2°, which was set in 2010. Finally, on August 27, Arctic sea ice extent was 4.157 million square kilometers (JAXA). There is an implied 93% probability that Arctic sea ice extent will reach a minimum figure below 4.000 million square kilometers for the second consecutive year and third time on record. The highest 25% bound is 3.857 million square kilometers. The lowest 25% bound is 3.618 million square kilometers.

This afternoon, the temperature rose into the middle 80s in New York City under mainly sunny skies. Four photos from The New York Botanical Garden: