donsutherland1

Morning thoughts... Today will be variably cloudy and pleasant. Temperatures will likely top out in the lower and middle and upper 70s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 74° Newark: 79° Philadelphia: 78° Tomorrow will be partly sunny and much warmer.

Tomorrow will be fair and comfortable. Another big push of warm air is likely Wednesday into Thursday. Another cooldown will follow. The Memorial Day weekend will likely be unsettled and cooler. Periods of rain are possible, though there is large uncertainty about the amount of precipitation. A light to perhaps moderate rainfall appears more likely than a heavy rainfall based on the ensembles. The first 7-10 days of June could start off warmer than normal. The MJO's passage through Phase 4 at an amplitude of 1.500 or above during the May 15-25 period coupled with ENSO Region 1+2 temperature anomalies above -1.0°C and below +1.0°C, as has been the case this year, has typically seen warmth in the East during the first 10 days of June. Cooler conditions typically prevailed when the ENSO Region 1+2 anomalies were outside that range. Neutral ENSO conditions have now developed. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.2°C for the week centered around May 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.78°C and the ENSO Region 3.4 anomaly has averaged -0.33°C. Neutral ENSO conditions will likely prevail into at least mid-summer. The SOI was -7.95 today. The preliminary Arctic Oscillation (AO) figure was +0.561 today. On May 22 the MJO was in Phase 5 at an amplitude of 1.756 (RMM). The May 21-adjusted amplitude was 1.644 (RMM). In late April, the MJO moved through Phase 8 at an extreme amplitude (+3.000 or above). Only February 25, 1988 and March 18-19, 2015 had a higher amplitude at Phase 8. Both 1988 and 2015 went on to have an exceptionally warm July-August period. July-August 1988 had a mean temperature of 79.1°, which ranked 4th highest for that two-month period. July-August 2015 had a mean temperature of 78.9°, which ranked 5th highest for that two-month period. September 2015 was also the warmest September on record. The MJO's extreme passage through Phase 8 could provide the first hint of a hot summer. Based on sensitivity analysis applied to the latest guidance, there is an implied 74% probability that New York City will have a warmer than normal May (1991-2020 normal). May will likely finish with a mean temperature near 64.3° (1.1° above normal).

Morning thoughts... The morning will feature plenty of clouds. However, it will become partly sunny this afternoon. It will be noticeably cooler than yesterday. Temperatures will likely top out in the 60s and perhaps some lower 70s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 67° Newark: 70° Philadelphia: 71° Tomorrow will be partly sunny and pleasant. Yesterday saw some record high minimum temperatures tied or broken at: Islip: 65° (old record: 63°, 2013); New York City-JFK: 68° (old record: 63°, 1980 and 2010); and, Newark: 68° (tied record set in 2013).

IMO, the statistical evidence (slight cooling in summer high temperatures at Central Park while the remainder of the region has warmed approximately one degree F) demonstrates that the summer records are inaccurate. One of three measures should be taken to preserve or restore data integrity: 1. Trees should be trimmed so that the ASOS is in compliance with customary practice 2. The ASOS should be moved to an alternative location in the Park that would be in compliance and also have limited risk of falling out of compliance anytime soon 3. Homogenization of the Central Park temperatures to bring them into line where they should be (some degree of error would exist) All three of these approaches are preferable to increasingly flawed summer data. I'd prefer the first two, but the third would be a useful resort were the first two not pursued.

The temperature rose to 90° or above in numerous locations for a second consecutive day. Areas reporting 90° temperatures included: Allentown: 90° Atlantic City: 94° (tied record set in 1964) Baltimore: 95° Bridgeport: 90° (old record: 89°, 1992) Boston: 90° Georgetown: 93° (tied record set in 1964) Harrisburg: 93° New York City-JFK: 92° (old record: 89°, 1964 and 1980) Newark: 94° Philadelphia: 92° Providence: 90° Sterling, VA: 92° (tied record set in 1964) Trenton: 90° Washington, DC: 94° Wilmington, DE: 94° (tied record set in 1925) Yesterday was the first day on record in May when Islip reached 90° or above while New York City's Central Park did not reach 90°. Today became the first day on record when Bridgeport reached 90° or above, but Central Park did not reach 90°. 90° Days for Select Cities (through May 23): Albany: 0 (2020: 13 days; 5-Year Average: 13.6 days) Allentown: 1 (2020: 24 days; 5-Year Average: 27.6 days) Baltimore: 2 (2020: 46 days; 5-Year Average: 44.6 days) Boston: 1 (2020: 14 days; 5-Year Average: 17.2 days) Bridgeport: 1 (2020: 11 days; 5-Year Average: 13.4 days) Burlington: 2 (2020: 20 days; 5-Year Average: 13.0 days) Harrisburg: 1 (2020: 35 days; 5-Year Average: 30.6 days) Hartford: 1 (2020: 39 days; 5-Year Average: 29.0 days) Islip: 1 (2020: 8 days; 5-Year Average: 9.4 days) New York City-JFK: 2 (2020: 12 days; 5-Year Average: 10.2 days) New York City-LGA: 0 (2020: 34 days; 5-Year Average: 29.4 days) New York City-NYC: 0 (2020: 20 days; 5-Year Average: 18.2 days) Newark: 3 (2020: 31 days; 5-Year Average: 31.2 days) Philadelphia: 2 (2020: 36 days; 5-Year Average: 34.6 days) Scranton: 1 (2020: 25 days; 5-Year Average: 16.4 days) Washington, DC: 3 (2020: 46 days; 5-Year Average: 50.8 days) New York City-Newark Average: 1 (2020: 22 days) ...Expected: 2 (based on regression equation tied to JFK-LGA-EWR data) To date, JFK Airport has recorded more 90° temperatures than both Central Park and LaGuardia Airport. Only 1978 and 1984 saw JFK report more 90° than both Central Park and LaGuardia Airport. Tomorrow and Tuesday will see a return of noticeably cooler air before another big push of warm air takes place. The dominant weather story into the closing week of May will be the synoptic impact of a strongly to occasionally severely negative PNA. That development will lead to a warmer to perhaps much warmer than normal second half of May. There will likely be at least one more day on which the temperature will make a run at 90° in parts of the region this week. Today, the preliminary value of the PNA was -1.121. The PNA will likely rise above -1.000 tomorrow. During the May 16-31, 1991-2020 period, the mean temperature was 65.2° in New York City and 67.0° in Philadelphia. When the PNA was -1.000 or below, the average temperature was 67.7° in New York City and 69.3° in Philadelphia. During the May 16-23 period, the likely mean temperatures will be 71.3° at New York City and Philadelphia 70.6° at Philadelphia. During the 1991-2020 period, 30% of days in New York City and 41% of days in Philadelphia had high temperatures of 80° or above. During the 1991-2020 period, 15% of days in New York City and 23% of days in Philadelphia had high temperatures of 85° or above. When the PNA was -1.000 or below during that period, 41% of days in New York City and 50% of days in Philadelphia had high temperatures of 80° or above. When the PNA was -1.000 or below during that period, 24% of days in New York City and 35% of days in Philadelphia had high temperatures of 85° or above. During the May 16-23 period, the temperature reached 80° or above on 50% of days and 85° or above on 38% of days in New York City. The temperature reached 80° or above on 75% of days and 85° or above on 38% of days in Philadelphia. In both cities, the warmth overperformed somewhat. As had been the case with April, the closing week of May could wind up warmer to much warmer than normal. In the four cases where the MJO reached Phase 1 at an amplitude of 2.000 or above in combination with a cool ENSO Region 3.4 anomaly during the May 1-10 period, as occurred this year, three wound up with warmer to much warmer than normal conditions. At New York City, the mean temperature during the closing 7 days of May was 72.7° during those three cases while it was 72.0° at Philadelphia. The 1991-2020 means were 67.9° and 69.7° respectively. Only May 25-31, 2013 (monthly ENSO Region 1+2 anomaly of -1.38°C) was cooler than normal. However, 90° heat arrived on May 29 in Philadelphia and May 30 in New York City during 2013. Nevertheless, the Memorial Day weekend will likely be unsettled and cooler. Periods of rain are possible, though there is large uncertainty about the amount of precipitation. A light to perhaps moderate rainfall appears more likely than a heavy rainfall based on the ensembles. The first 7-10 days of June could also start off warmer than normal. The MJO's passage through Phase 4 at an amplitude of 1.500 or above during the May 15-25 period coupled with ENSO Region 1+2 temperature anomalies above -1.0°C and below +1.0°C, as has been the case this year, has typically seen warmth in the East during the first 10 days of June. Cooler conditions typically prevailed when the ENSO Region 1+2 anomalies were outside that range. Neutral ENSO conditions have now developed. The ENSO Region 1+2 anomaly was -0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around May 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.75°C and the ENSO Region 3.4 anomaly has averaged -0.38°C. Neutral ENSO conditions will likely prevail into at least mid-summer. The SOI was +6.68 today. The preliminary Arctic Oscillation (AO) figure was +1.261 today. On May 21 the MJO was in Phase 4 at an amplitude of 1.644 (RMM). The May 20-adjusted amplitude was 1.863 (RMM). In late April, the MJO moved through Phase 8 at an extreme amplitude (+3.000 or above). Only February 25, 1988 and March 18-19, 2015 had a higher amplitude at Phase 8. Both 1988 and 2015 went on to have an exceptionally warm July-August period. July-August 1988 had a mean temperature of 79.1°, which ranked 4th highest for that two-month period. July-August 2015 had a mean temperature of 78.9°, which ranked 5th highest for that two-month period. September 2015 was also the warmest September on record. The MJO's extreme passage through Phase 8 could provide the first hint of a hot summer. Based on sensitivity analysis applied to the latest guidance, there is an implied 80% probability that New York City will have a warmer than normal May (1991-2020 normal). May will likely finish with a mean temperature near 64.5° (1.3° above normal).

The tree issue was much smaller back in 1993 than it is today. JFK has reached a high of 90° so far.

Changes in Summer (June-August) Average High Temperatures (1971-00 vs. 1991-20 Means): Bridgeport: +0.9° Islip: +1.3° New Brunswick: +1.4° New York City-JFK: +1.0° New York City-LGA: +1.6° Newark: +0.8° Poughkeepsie: +1.1° White Plains: +1.0° Average: +1.1° Median: +1.1° Standard Deviation: +0.3° Trimmed Mean (excluding the highest and lowest changes): +1.1° Second Trimmed Mean (excluding the two highest and lowest changes): +1.1° New York City-Central Park: -0.1° (more than 3 sigma below the regional change excluding Central Park) Note: The tree obstructions at Central Park were noted beginning in 1992

These are the occurrences: July 1, 1963: JFK: 102; NYC: 98 July 4, 1966: JFK: 101; NYC: 98 July 23, 1972: JFK: 100; NYC: 94 July 16, 1983: JFK: 100; NYC: 96 August 20, 1983: JFK: 100; NYC: 96 July 4, 2010: JFK: 101; NYC: 96 July 18, 2013: JFK: 100; NYC: 98

Morning thoughts... Today will be partly sunny and hot. Temperatures will likely reach the upper 80s to lower 90s in most of the region. A few areas could experience an afternoon or evening thundershower. Likely high temperatures around the region include: New York City (Central Park): 91° Newark: 95° Philadelphia: 93° Tomorrow will be noticeably cooler.

I am not aware of any.

The temperature rose into the upper 80s and lower 90s across much of the region today. 90° or above temperatures were reported at: Atlantic City: 94° (old record: 91°, 1992) Baltimore: 93° Georgetown, DE: 93° (old record: 92°, 1996) Hartford: 90° Islip: 90° New York City-JFK: 94° (tied record set in 1992) Newark: 96° Philadelphia: 92° Washington, DC: 91° Wilmington, DE: 92° The high temperature at Central Park was 89°. Today was the first day on record in May where Central Park had a temperature below 90° while Islip had a high temperature of 90° or above. It was also the first day on record where Central Park had a high temperature below 90° and both Islip and JFK Airport saw 90° or above high temperatures. Prior to today, there were two cases in May where JFK Airport had a high temperature of 90° or above while Central Park did not reach 90°: May 13, 1956: JFK: 90°; NYC: 89° May 21, 1962: JFK: 90°; NYC: 87° Bridgeport reached 87°. That broke the daily record of 85°, which was set in 1991 and tied in 1992. Tomorrow will feature more unseasonable warmth. Temperatures will generally reach the upper 80s and lower 90s across much of the region. Exceptions would be coastal areas prone to sea breezes. The dominant weather story into the closing week of May will be the synoptic impact of a strongly to occasionally severely negative PNA. That development will lead to a warmer to perhaps much warmer than normal second half of May. There will likely be additional days on which the temperature will make a run at 90° in parts of the region. Today, the preliminary value of the PNA was -1.519. The PNA is forecast to remain at or below -1.000 until around May 24. During the May 16-31, 1991-2020 period, the mean temperature was 65.2° in New York City and 67.0° in Philadelphia. When the PNA was -1.000 or below, the average temperature was 67.7° in New York City and 69.3° in Philadelphia. During the 1991-2020 period, 30% of days in New York City and 41% of days in Philadelphia had high temperatures of 80° or above. During the 1991-2020 period, 15% of days in New York City and 23% of days in Philadelphia had high temperatures of 85° or above. When the PNA was -1.000 or below during that period, 41% of days in New York City and 50% of days in Philadelphia had high temperatures of 80° or above. When the PNA was -1.000 or below during that period, 24% of days in New York City and 35% of days in Philadelphia had high temperatures of 85° or above. As had been the case with April, the closing week of May could wind up warmer to much warmer than normal. In the four cases where the MJO reached Phase 1 at an amplitude of 2.000 or above in combination with a cool ENSO Region 3.4 anomaly during the May 1-10 period, as occurred this year, three wound up with warmer to much warmer than normal conditions. At New York City, the mean temperature during the closing 7 days of May was 72.7° during those three cases while it was 72.0° at Philadelphia. The 1991-2020 means were 67.9° and 69.7° respectively. Only May 25-31, 2013 (monthly ENSO Region 1+2 anomaly of -1.38°C) was cooler than normal. However, 90° heat arrived on May 29 in Philadelphia and May 30 in New York City during 2013. The first 7-10 days of June could also start off warmer than normal. The MJO's passage through Phase 4 at an amplitude of 1.500 or above during the May 15-25 period coupled with ENSO Region 1+2 temperature anomalies above -1.0°C and below +1.0°C, as has been the case this year, has typically seen warmth in the East during the first 10 days of June. Cooler conditions typically prevailed when the ENSO Region 1+2 anomalies were outside that range. Neutral ENSO conditions have now developed. The ENSO Region 1+2 anomaly was -0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around May 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.75°C and the ENSO Region 3.4 anomaly has averaged -0.38°C. Neutral ENSO conditions will likely prevail into at least mid-summer. The SOI was +1.63 today. The preliminary Arctic Oscillation (AO) figure was +1.092 today. On May 20 the MJO was in Phase 4 at an amplitude of 1.863 (RMM). The May 19-adjusted amplitude was 1.915 (RMM). In late April, the MJO moved through Phase 8 at an extreme amplitude (+3.000 or above). Only February 25, 1988 and March 18-19, 2015 had a higher amplitude at Phase 8. Both 1988 and 2015 went on to have an exceptionally warm July-August period. July-August 1988 had a mean temperature of 79.1°, which ranked 4th highest for that two-month period. July-August 2015 had a mean temperature of 78.9°, which ranked 5th highest for that two-month period. September 2015 was also the warmest September on record. The MJO's extreme passage through Phase 8 could provide the first hint of a hot summer. Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal May (1991-2020 normal). May will likely finish with a mean temperature near 64.6° (1.4° above normal).

The high temperature at Central Park was 89°. Today was the first day on record in May where Central Park had a temperature below 90° while Islip had a high temperature of 90° or above. It was also the first day on record where Central Park had a high temperature below 90° and both Islip and JFK Airport saw 90° or above high temperatures. Prior to today, there were two cases in May where JFK Airport had a high temperature of 90° or above while Central Park did not reach 90°: May 13, 1956: JFK: 90°; NYC: 89° May 21, 1962: JFK: 90°; NYC: 87°

Despite high- and mid-level clouds that dimmed the sun, the temperature rose into the upper 80s in the New York City area and lower 90s in adjacent New Jersey. Peonies remain in bloom at the New York Botanical Garden. Irises have exploded into bloom.

1906 9 days 1908 12 days

Morning thoughts... Today will be partly sunny and hot. Temperatures will likely reach the upper 80s to lower 90s in most of the region. A few areas could experience an afternoon or evening thundershower. Likely high temperatures around the region include: New York City (Central Park): 90° Newark: 93° Philadelphia: 91° Tomorrow will be another partly sunny and very warm day.

It was probably a combination of the increased urbanization around LGA--now New York City's premier heat island--and the more recent increase in vegation in Central Park. As a result, the relationship between the two locations weakened as far as 90° days was concerned. Annual 90° Days (30-Year Average): 1951-80: LGA: 14.8; NYC: 18.3 1961-90: LGA: 13.7; NYC: 18.3 1971-00: LGA: 15.1; NYC: 18.1 1981-10: LGA: 18.7; NYC: 17.4 1991-20: LGA: 21.8; NYC: 17.4 The 30-year average for annual 90° days at LGA surpassed NYC for the first time during the 1978-2007 period. Annual 90° Days (1950-2020 broken into two parts): 1950-1984: LGA: 14.7; NYC: 18.0 (coefficient of determination: 0.686) 1985-2020: LGA: 21.0; NYC: 17.5 (coefficient of determination: 0.619)

MPO has not yet hit 90.

It’s a little above that.

Temperatures in the northern Middle Atlantic and southern New England areas rose into the 70s and 80s today. Some 90° temperatures were reported. Burlington reached 90° for the second consecutive day and second time this month. Only 10 years saw May record 2 or more 90° temperatures and 9 years saw 2 or more consecutive such temperatures in May. The last time there were 2 or more 90° readings in May and 2 or more consecutive such temperatures was 2020. Syracuse reached 93°. 90° Days for Select Cities (through May 21): Albany: 0 (2020: 13 days; 5-Year Average: 13.6 days) Allentown: 0 (2020: 24 days; 5-Year Average: 27.6 days) Baltimore: 0 (2020: 46 days; 5-Year Average: 44.6 days) Boston: 0 (2020: 14 days; 5-Year Average: 17.2 days) Bridgeport: 0 (2020: 11 days; 5-Year Average: 13.4 days) Burlington: 2 (2020: 20 days; 5-Year Average: 13.0 days) Harrisburg: 0 (2020: 35 days; 5-Year Average: 30.6 days) Hartford: 0 (2020: 39 days; 5-Year Average: 29.0 days) Islip: 0 (2020: 8 days; 5-Year Average: 9.4 days) New York City-JFK: 0 (2020: 12 days; 5-Year Average: 10.2 days) New York City-LGA: 0 (2020: 34 days; 5-Year Average: 29.4 days) New York City-NYC: 0 (2020: 20 days; 5-Year Average: 18.2 days) Newark: 1 (2020: 31 days; 5-Year Average: 31.2 days) Philadelphia: 0 (2020: 36 days; 5-Year Average: 34.6 days) Scranton: 1 (2020: 25 days; 5-Year Average: 16.4 days) Washington, DC: 1 (2020: 46 days; 5-Year Average: 50.8 days) New York City-Newark Average: 0 (2020: 22 days) ...Expected: 0 (based on regression equation tied to JFK-LGA-EWR data) In Quebec, daily record high temperatures were set in Montreal: 89° (old record: 87°, 1977) and Trois-Rivières: 84° (old record: 79°, 2012) Much warmer weather is likely for the weekend. Temperatures will generally reach the upper 80s and lower 90s across much of the region. Exceptions would be coastal areas prone to sea breezes. The dominant weather story into at least the closing week of May will be the synoptic impact of a strongly to occasionally severely negative PNA. That development will lead to a warmer to perhaps much warmer than normal second half of May. There will likely be additional days on which the temperature will make a run at 90° in parts of the region. Today, the preliminary value of the PNA was -1.457. The PNA is forecast to remain at or below -1.000 until around May 24. During the May 16-31, 1991-2020 period, the mean temperature was 65.2° in New York City and 67.0° in Philadelphia. When the PNA was -1.000 or below, the average temperature was 67.7° in New York City and 69.3° in Philadelphia. During the 1991-2020 period, 30% of days in New York City and 41% of days in Philadelphia had high temperatures of 80° or above. During the 1991-2020 period, 15% of days in New York City and 23% of days in Philadelphia had high temperatures of 85° or above. When the PNA was -1.000 or below during that period, 41% of days in New York City and 50% of days in Philadelphia had high temperatures of 80° or above. When the PNA was -1.000 or below during that period, 24% of days in New York City and 35% of days in Philadelphia had high temperatures of 85° or above. As had been the case with April, the closing week of May could wind up warmer to much warmer than normal. In the four cases where the MJO reached Phase 1 at an amplitude of 2.000 or above in combination with a cool ENSO Region 3.4 anomaly during the May 1-10 period, as occurred this year, three wound up with warmer to much warmer than normal conditions. At New York City, the mean temperature during the closing 7 days of May was 72.7° during those three cases while it was 72.0° at Philadelphia. The 1991-2020 means were 67.9° and 69.7° respectively. Only May 25-31, 2013 (monthly ENSO Region 1+2 anomaly of -1.38°C) was cooler than normal. However, 90° heat arrived on May 29 in Philadelphia and May 30 in New York City during 2013. The first 7-10 days of June could also start off warmer than normal. The MJO's passage through Phase 4 at an amplitude of 1.500 or above during the May 15-25 period coupled with ENSO Region 1+2 temperature anomalies above -1.0°C and below +1.0°C, as has been the case this year, has typically seen warmth in the East during the first 10 days of June. Cooler conditions typically prevailed when the ENSO Region 1+2 anomalies were outside that range. Neutral ENSO conditions have now developed. The ENSO Region 1+2 anomaly was -0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around May 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.75°C and the ENSO Region 3.4 anomaly has averaged -0.38°C. Neutral ENSO conditions will likely prevail into at least mid-summer. The SOI was +0.86 today. The preliminary Arctic Oscillation (AO) figure was -0.024 today. On May 19 the MJO was in Phase 4 at an amplitude of 1.914 (RMM). The May 18-adjusted amplitude was 1.703 (RMM). In late April, the MJO moved through Phase 8 at an extreme amplitude (+3.000 or above). Only February 25, 1988 and March 18-19, 2015 had a higher amplitude at Phase 8. Both 1988 and 2015 went on to have an exceptionally warm July-August period. July-August 1988 had a mean temperature of 79.1°, which ranked 4th highest for that two-month period. July-August 2015 had a mean temperature of 78.9°, which ranked 5th highest for that two-month period. September 2015 was also the warmest September on record. The MJO's extreme passage through Phase 8 could provide the first hint of a hot summer. Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal May (1991-2020 normal). May will likely finish with a mean temperature near 64.7° (1.5° above normal).

The increased fraction of flooded area likely included some important and costly infrastructure.

Morning thoughts... Today will be partly to mostly sunny and warm. Temperatures will likely reach the upper 70s to lower 80s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 79° Newark: 83° Philadelphia: 84° A much warmer weekend lies ahead.

Despite ample sunshine, the northern Middle Atlantic and southern New England regions were cooler than yesterday. Nevertheless, a few locations reached 90° in the Northeast this afternoon. Those locations included: Burlington: 92° (old record: 91°, 1975); Scranton: 90°; and, Washington, DC: 93°. 90° temperatures at Burlington have become more common during the month of May in recent years. Some statistics for May 1981-2020: 1981-2010: Mean Monthly High: 85.2°; 0.3 90° days each May 1991-2020: Mean Monthly High: 86.3°; 0.4 90° days each May 2010-2020: Mean Monthly High: 88.5°; 0.8 90° days each May Tomorrow will be fair and pleasant in the northern Middle Atlantic and southern New England areas with temperatures holding mainly in the 70s. Lower 80s are possible in central and southern New Jersey southward. Much warmer weather is likely for the weekend. The dominant weather story into at least the closing week of May will be the synoptic impact of a strongly to occasionally severely negative PNA. That development will lead to a warmer to perhaps much warmer than normal second half of May. There will likely be additional days on which the temperature will make a run at 90° in parts of the region. Today, the preliminary value of the PNA was -1.584. The PNA is forecast to remain at or below -1.000 until around May 24. During the May 16-31, 1991-2020 period, the mean temperature was 65.2° in New York City and 67.0° in Philadelphia. When the PNA was -1.000 or below, the average temperature was 67.7° in New York City and 69.3° in Philadelphia. During the 1991-2020 period, 30% of days in New York City and 41% of days in Philadelphia had high temperatures of 80° or above. During the 1991-2020 period, 15% of days in New York City and 23% of days in Philadelphia had high temperatures of 85° or above. When the PNA was -1.000 or below during that period, 41% of days in New York City and 50% of days in Philadelphia had high temperatures of 80° or above. When the PNA was -1.000 or below during that period, 24% of days in New York City and 35% of days in Philadelphia had high temperatures of 85° or above. As had been the case with April, the closing week of May could wind up warmer to much warmer than normal. In the four cases where the MJO reached Phase 1 at an amplitude of 2.000 or above in combination with a cool ENSO Region 3.4 anomaly during the May 1-10 period, as occurred this year, three wound up with warmer to much warmer than normal conditions. At New York City, the mean temperature during the closing 7 days of May was 72.7° during those three cases while it was 72.0° at Philadelphia. The 1991-2020 means were 67.9° and 69.7° respectively. Only May 25-31, 2013 (monthly ENSO Region 1+2 anomaly of -1.38°C) was cooler than normal. However, 90° heat arrived on May 29 in Philadelphia and May 30 in New York City during 2013. Neutral ENSO conditions have now developed. The ENSO Region 1+2 anomaly was -0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around May 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.75°C and the ENSO Region 3.4 anomaly has averaged -0.38°C. Neutral ENSO conditions will likely prevail into at least mid-summer. The SOI was +8.14 today. The preliminary Arctic Oscillation (AO) figure was -0.587 today. On May 18 the MJO was in Phase 3 at an amplitude of 1.702 (RMM). The May 17-adjusted amplitude was 1.749 (RMM). In late April, the MJO moved through Phase 8 at an extreme amplitude (+3.000 or above). Only February 25, 1988 and March 18-19, 2015 had a higher amplitude at Phase 8. Both 1988 and 2015 went on to have an exceptionally warm July-August period. July-August 1988 had a mean temperature of 79.1°, which ranked 4th highest for that two-month period. July-August 2015 had a mean temperature of 78.9°, which ranked 5th highest for that two-month period. September 2015 was also the warmest September on record. The MJO's extreme passage through Phase 8 could provide the first hint of a hot summer. Based on sensitivity analysis applied to the latest guidance, there is an implied 80% probability that New York City will have a warmer than normal May (1991-2020 normal). May will likely finish with a mean temperature near 64.6° (1.4° above normal).

It reached a daily record 92 today.

Morning thoughts... Today will be partly to mostly sunny and very warm. Temperatures will likely reach the middle and upper 70s in most of the region. Temperatures will likely reach the lower 80s from central New Jersey southward. Likely high temperatures around the region include: New York City (Central Park): 76° Newark: 78° Philadelphia: 83° Tomorrow will be partly cloudy and mild.

Nothing that I can recall anytime recently. Unfortunately, model data isn’t archived—at least publicly—so one can’t look for such dramatic swings.