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September 2020 wx discussion

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2010's was the warmest decade...the 1950's was the driest...

September decade averages...

Decade...ave temp...rainfall...ave max...ave min...

1870's......65.3......3.41"............................

1880's......66.2......4.18"......86.5......46.1

1890's......67.7......3.38"......89.6......47.0

1900's......68.1......3.84"......86.8......48.4

1910's......66.8......3.09"......89.5......45.6

1920's......67.8......3.54"......91.1......47.2

1930's......68.7......5.15"......90.0......47.9

1940's......68.8......3.70"......91.2......45.5

1950's......68.3......2.36"......89.9......45.6

1960's......67.7......3.85"......90.2......47.2

1970's......68.3......4.73"......90.1......47.1

1980's......68.6......3.58"......90.3......47.5

1990's......68.0......4.18"......88.7......47.6

2000's......68.6......4.91"......86.5......49.7

2010's......70.5......3.67"......92.2......52.7

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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.

 

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8 minutes ago, donsutherland1 said:

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.

 

Has there ever been a La Nina winter where the month of September winds up being below normal? If so, what was that winter like?

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5 minutes ago, TriPol said:

Has there ever been a La Nina winter where the month of September winds up being below normal? If so, what was that winter like?

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

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1 minute ago, donsutherland1 said:

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

I remember a Norlun in Suffolk some time in mid December 1988. 

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1 hour ago, donsutherland1 said:

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

the warmer la nina septembers led to more snow on average for the next winter than the colder ones......

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1 hour ago, uncle W said:

the warmer la nina septembers led to more snow on average for the next winter than the colder ones......

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

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The next 8 days are averaging 67degs.      Make it 62degs., or -5.0.

52*!(44%RH) here at 6:00am, m. clear.   51* at 6:30am        56* by 11am.

No precipitation till the 29th +/- a day, or any model.      EURO now ups the T's for the next 10 days, while the GFS backs them down.

Tropics quieting down:    26N 93W,  25N 59W-still getting stronger, but I am just a strawman, 13N 37W-going nowhere?

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9 hours ago, donsutherland1 said:

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

HM tweeted a study on the effects of the major wildfires going on out west....it dramatically affects stratospheric conditions for the winter: 

 

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The low of 50° in NYC was the coldest September temperature since 2013. Early Sunday could be a degree or two cooler. 
 

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Sep
Click column heading to sort ascending, click again to sort descending.
Year
Lowest Min Temperature 
Missing Count
2020 50 11
2019 52 0
2018 54 0
2017 54 0
2016 54 0
2015 56 0
2014 52 0
2013 47 0
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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°

 

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49 for the low this morning, currently 58.

51 degrees with a strong breeze at 4 AM felt like 25 degrees to my summer acclimated self. Too early for this.

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14 minutes ago, jfklganyc said:

47F this am.

 

I’ll be the one to say it… It’s too early for this shit… Especially with this pandemic going on.

Of all years we needed warm weather and a pleasant fall

Would you prefer 90 in October?

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We know from recent experience that these cool downs don’t last very long around here. Both the Euro and GFS generate more near 100° heat in portions of the Plains next week. This would just add to the record extremes that have occurred this month. So more 80s later this month for our area look like a good bet. Wouldn’t take much to make a run on 90° if the winds can go SW with enough sun.

 

24EE1B8D-871D-4219-8AAE-6D9401F80C08.thumb.png.0232236fa86656f2101d6242e7b63c26.png

 

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23 minutes ago, jfklganyc said:

If it means keeping outdoor spaces open, case counts down, and my kids going to school...hell yes!

Agree 100%. The more fresh air we can keep in buildings the better. Schools right now need to exchange air at least 4 times an hour and that is much harder to do when you have to heat it from freezing. Also, even though indoor dining is open, I still won't do it right now. Had a few coronavirus scares personally both in the spring and this fall. I teach at the university level and have been trying to do some in-person teaching. I love winter and all that, but let's hope we can keep windows open as late as possible.

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Down to 43 last night and up to a chilly but sunny 60 now.  Cool next 3 days as well highlighted here. Warm up by Wed (9/23) and overall warmer near or above normal looks likely to take us to the end of the month.  We'll see how much of the stronger warmth can get into the east timing -wise that looks between Friday (9/25) and Mon (9/28).

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Updated last few days 

 

9/17

EWR: 77
LGA: 77
ACY: 77
TEB: 76
ISP: 76
PHL: 76
New Brnswck: 76
NYC: 75
BLM: 74
JFK: 74
TTN: 74

------------------------------------------------------------------------------------------------------------------------

9/18

EWR: 73
JFK: 72
PHL: 72
LGA: 71
TEB: 71
BLM: 71
New brnswck: 71
ACY: 71
NYC: 70
TTN: 70
ISP: 69
 

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