donsutherland1

Morning thoughts... The coldest air so far this season remains in place. Today will be partly sunny and still very cool for the season. The temperature will likely top out in the lower and middle 60s across the region. Likely high temperatures around the region include: New York City (Central Park): 64° Newark: 65° Philadelphia: 66° Toward the middle of this week, a warmer pattern will develop. In terms of verification, here's how last evening's estimates worked out: Albany: 35°; Actual: 34° Allentown: 39°; Actual: 36° Boston: 46°; Actual: 44° Bridgeport: 47°; Actual: 49° Harrisburg: 42°; Actual: 43° Hartford: 38°; Actual: 36° Islip: 48°; Actual: 48° New York City: 48°; Actual: 50° Newark: 47°; Actual: 48° Philadelphia: 47°; Actual: 47° Poughkeepsie: 37°; Actual: 36° Providence: 44°; Actual: 46° White Plains: 42°; Actual: 45° Average Error: 1.5°

Temperatures reached only the lower and middle 60s across the region today despite bright sunshine. Tomorrow morning, Central Park will likely have a minimum temperature below 50°. The last time the temperature fell into the 40s in New York City during September was September 24, 2013 when the temperature fell to 47°. Select low temperature estimates include: Albany: 35° Allentown: 39° Boston: 46° Bridgeport: 47° Harrisburg: 42° Hartford: 38° Islip: 48° New York City: 48° Newark: 47° Philadelphia: 47° Poughkeepsie: 37° Providence: 44° White Plains: 42° Generally below normal readings could persist until near the middle of next week. Afterward, temperatures will moderate with temperatures returning to above normal levels for much of the remainder of the month. Today, Denver hit 90°. That was the 74th time this year that the temperature reached or exceeded 90° at Denver. The prior record was 73 days, which was set in 2012. The 30-year moving average of 90° days has also been increasing. Since 2000, Denver has added an average of 9.5 such days to its annual figure. Since 1950, the annual average has increased by just over 90% to an average of 44.6 days. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.75°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +10.28. Today, the preliminary Arctic Oscillation (AO) figure was +1.003. On September 18, the MJO was in Phase 4 at an amplitude of 1.290 (RMM). The September 17-adjusted amplitude was 1.587. 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°. 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 54% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.2°.

Denver isn’t far from the Sonoran Desert. Heat can easily push through the Rockies and into the Northern Plains. There are no large water bodies to moderate the heat.

I suspect that the issue is a function of the reality that people, in general, are very poor at risk perception. Biases skew perceptions. What happened at Chernobyl and Three Mile Island looms large in perceptions of risk. In reality, when carbon pollution from fossil fuels is considered, there’s little debate. Fossil fuels are the more hazardous energy source.

Under mostly sunny skies, the temperature rose into the lower 60s at Robert Moses State Park this afternoon. A few Monarch butterflies were in flight, but the peak migration is still a little in the future, as much of the goldenrod has yet to bloom. Five photos from today:

Today, Denver hit 90°. That was the 74th time this year that the temperature reached or exceeded 90° at Denver. The prior record was 73 days, which was set in 2012. The five highest number of 90° days during a year are: 1. 74, 2020 2. 73, 2012 3. 61, 2000 4. 60, 1994 5. 59, 2018 The 30-year moving average of 90° days has also been increasing. Since 2000, Denver has added an average of 9.5 such days to its annual figure. Since 1950, the annual average has increased by just over 90%. Select statistics for the 30-year period ending in the specified years: 1950 23.3 days 1960 29.8 days 1970 29.8 days 1980 34.5 days 1990 33.8 days 2000 35.1 days 2010 37.8 days 2020 44.6 days Since recordkeeping began in 1872, Denver has had 16 years during which there were 50 or more 90° readings. 11 (69%) have occurred during 2000 or later and 6 (38%) have occurred during 2010 or later. The exceptional heat of summer 2020 and early September 2020 made this outcome possible. Denver's average high temperature during summer 2020 was 91.2°, which is the second highest figure on record. Such summers are likely to become more common in the years ahead with the average high temperature during summer likely to increase by nearly 1°F under the RCP 4.5 scenario by 2030 (and 2.9° from the 1981-2020 base figure).

Courtesy of a paper noted by @snowman19 here’s a link to a paper that might be of interest: https://www.nature.com/articles/s41612-018-0039-3

Morning thoughts... The coldest air so far this season now covers the region. Today will be partly sunny and very cool for the season. The temperature will likely struggle toward the middle 60s across the region. Likely high temperatures around the region include: New York City (Central Park): 64° Newark: 65° Philadelphia: 65° A warmup will likely commence toward the middle of next week. In terms of verification, here's how last evening's estimates worked out: Albany: 36°; Actual: 33° Allentown: 41°; Actual: 39° Boston: 48°; Actual: 46° Bridgeport: 49°; Actual: 47° Harrisburg: 47°; Actual: 43° Hartford: 42°; Actual: 37° Islip: 48°; Actual: 49° New York City: 50°; Actual: 50° Newark: 49°; Actual: 48° Philadelphia: 50°; Actual: 48° Poughkeepsie: 40°; Actual: 36° Providence: 46°; Actual: 45° White Plains: 44°; Actual: 42° Average Error: 2.2°

While Phoenix was recording its hottest month on record in August, after having set the mark in July, the United Kingdom experienced a severe heat wave in August. Here’s a link to a post written by two UK Met Office authors: https://www.carbonbrief.org/met-office-the-uks-august-2020-heatwave Excerpt: During August 2020, temperatures exceeding 34C were recorded somewhere in the UK for six consecutive days. 34C has been recorded in the UK during seven out of the last 10 years, compared to seven out of the previous 50 years from 1961 to 2010. This suggests that temperatures of 34C or higher occurring at some point during the summer are becoming a more common occurrence.

Let’s hope this is an exception. The Euro seasonal outlook is ugly.

1988-89 and 2000-01 are examples. The former had below normal snowfall. The latter was snowier than normal.

The coming weekend will be unseasonably chilly. Even Central Park could see the temperature drop below 50° this weekend for the first time in September since September 24, 2013 when the temperature fell to 47°. Tomorrow morning's low temperatures will likely be near the following values: Albany: 36° Allentown: 41° Boston: 48° Bridgeport: 49° Harrisburg: 47° Hartford: 42° Islip: 48° New York City: 50° Newark: 49° Philadelphia: 50° Poughkeepsie: 40° Providence: 46° White Plains: 44° Generally below normal readings could persist until near the middle of next week. Afterward, temperatures will moderate. There is an increasing possibility that September could wind up on the cool side of normal, which would be an uncommon event in recent cases preceding La Niña winters. Such an outcome is not assured. The highest rainfall from Hurricane Sally was 29.99" at Orange Beach, AL. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.75°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +17.89. Today, the preliminary Arctic Oscillation (AO) figure was +0.407. On September 17, the MJO was in Phase 4 at an amplitude of 1.592 (RMM). The September 16-adjusted amplitude was 1.624. 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°. 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 49% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.1°. Finally, on September 17, Arctic sea ice extent (JAXA) was 3.735 million square kilometers. It is likely that the summer minimum figure has been reached. That figure was 3.555 million square kilometers (JAXA), which was the second lowest minimum extent on record. 2020 is the second consecutive year with a minimum extent figure below 4.000 million square kilometers and the third such year on record.

It still varies quite a bit.

Here is another paper: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JD015065

Morning thoughts... A strong cold front is moving across the area. Clouds will gradually give way to partly sunny skies. Temperatures will rise mainly into the upper 60s to around 70° across the region. Likely high temperatures around the region include: New York City (Central Park): 69° Newark: 70° Philadelphia: 70° This weekend will see the coolest readings so far this season.

On JAXA, Arctic sea ice extent rose to 3.735 million square kilometers. The 2020 minimum figure was 3.555 million square kilometers. That figure will very likely be the final minimum extent for 2020.

Here’s one paper that shows increasing water vapor: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JD024917 I’m not sure if NASA makes the underlying data for its cloud fraction maps public.

Today saw temperatures top out in the middle and upper 70s. However, this warmth will be short-lived. The coldest air mass so far this season will begin to overspread the region tomorrow. The coming weekend will be unseasonably chilly. Even Central Park could see the temperature drop below 50° for the first time in September since September 24, 2013 when the temperature fell to 47°. Generally below normal readings could persist into at least the last week of September. There is an increasing possibility that September could wind up on the cool side of normal, which would be an uncommon event in recent cases preceding La Niña winters. Elsewhere, Phoenix reached 109° today, which tied the daily record set in 1962. Today was also the 120th time this year that Phoenix reached 100° or above. 2020 is just the 7th year on record with 120 or more 100° readings. The last such year was 2018 with 128 days. The 30-year moving average is now 110.5 days. The 30-year moving average in 2010 was 109.6 days. Records go back to August 1895. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.75°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +17.89. Today, the preliminary Arctic Oscillation (AO) figure was +0.292. On September 16, the MJO was in Phase 4 at an amplitude of 1.620 (RMM). The September 15-adjusted amplitude was 1.428. 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°. 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 48% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.1°. Finally,on September 16, Arctic sea ice extent (JAXA) was 3.630 million square kilometers. To date, the summer minimum figure is 3.555 million square kilometers (JAXA). Based on 2010-2019 data, the highest 25% bound was 3.742 million square kilometers. The lowest 25% bound was 3.581 million square kilometers. The lowest 10% bound is 3.465 million square kilometers. 2020 is the second consecutive year with a minimum extent figure below 4.000 million square kilometers and the third such year on record. 2020 also has, by far, the second lowest extent on record. In contrast, according to NSIDC historical data, the 1920 minimum extent was approximately 8.826 million square kilometers and the 1970 minimum extent was 8.757 million square kilometers.

Here’s the attribution report on the Siberian heat: https://www.worldweatherattribution.org/wp-content/uploads/WWA-Prolonged-heat-Siberia-2020.pdf

There was additional rainfall. However, it seems that unlike a few years ago, WPC no longer provides precipitation amounts for ongoing events.

I agree. The NHC is very clear what a tropical cyclone is: " A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center." This is a very active season on account of developing La Nina conditions, wet conditions in Africa, and abnormally warm Atlantic waters. Prior to the season, NOAA, Colorado State, and Penn State forecasters all called near-record to possible record tropical activity.

Morning thoughts... Clouds have overspread much of the region from southeastern New York State southward. However, there remain breaks in the clouds back in a large part of Pennsylvania. As a result, today will be variably cloudy. It will also be warmer than yesterday. Temperatures will likely reach the middle and upper 70s across the region. Likely high temperatures around the region include: New York City (Central Park): 76° Newark: 78° Philadelphia: 77° An even colder air mass than the the most recent cold shot will likely begin overspreading the region tomorrow. The coming weekend will see the coolest readings so far this season. Farther south, the heavy rains from Sally are now moving out of the greater Atlanta area after dropping 3.57" rain from yesterday into early this morning. Sally's rains have moved into Greenville and will later be advancing into Charlotte and Fayetteville.

It is. This year’s record low ice in the central Arctic region, as part of a long-term trend of declining ice, is an example.

This is another significant paper. It confirms exactly what one would expect from the prior research showing a slowing and more wavy jet stream. It provides a unifying explanation for such events as last summer’s historic heat in Europe and Alaska, this year’s heat in Siberia, the record summer in parts of the Southwest, not to mention slowing forward motion of some recent hurricanes.

Temperatures rose into the lower and middle 70s today. Tomorrow will likely be several degrees warmer. Parts of the Southwest experienced record-tying and record-breaking heat. High temperatures included: Needles, CA: 112° (old record: 111°, 1924 and 2000) Phoenix: 109° (tied record set in 1928) Yuma, AZ: 111° (tied record set in 1922 and 2013) More record heat covered parts of Europe today. High temperatures in France included: Belin Beliet: 93° Chateauvillain: 98° Chablis: 94° Cogolin: 93° Durban-Corbières: 95° Montignac: 93° An even cooler air mass than the most recent one could arrive late in the week. Generally below normal readings could persist into at least the last week of September. There is an increasing possibility that September could wind up on the cool side of normal, which would be an uncommon event in recent cases preceding La Niña winters. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.75°C. La Niña conditions have developed and will likely prevail through the remainder of autumn. The SOI was +14.09. Today, the preliminary Arctic Oscillation (AO) figure was -0.096. On September 15, the MJO was in Phase 4 at an amplitude of 1.428 (RMM). The September 14-adjusted amplitude was 1.033. 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°. 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 48% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.3°. Finally,on September 15, Arctic sea ice extent (JAXA) was 3.606 million square kilometers. To date, the summer minimum figure is 3.555 million square kilometers (JAXA). Based on 2010-2019 data, the highest 25% bound was 3.742 million square kilometers. The lowest 25% bound was 3.581 million square kilometers. The lowest 10% bound is 3.465 million square kilometers. 2020 is the second consecutive year with a minimum extent figure below 4.000 million square kilometers and the third such year on record. 2020 also has, by far, the second lowest extent on record. In contrast, according to NSIDC historical data, the 1920 minimum extent was approximately 8.826 million square kilometers and the 1970 minimum extent was 8.757 million square kilometers.