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September 2020 wx discussion


forkyfork
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79/66 now and partly sunny.  About 3 - 4 hours of mainly partly sunny skies before more clouds move in. We'll see how high we can get today.  Potential for 90s but clouds may get in the way along with pop up storms.  Labor Day weekend looks spectacula.  Fri warm mid / upper 80s with cooler Sat and Sun before a bit warmer and humid Monday (9/7)

WC ridge, Western Atlantic Ridge expanding west from the NE with trough into the MW/GL.  Reminiscent of late May and Mid June onshore bananza  9/8 - 9/13.  Pending on the flow SE, ESE or E - will determine day time highs but overall warmer than normal, drier with cool and rain staying well west of the area.    Tropics need to be watched in the 9/9 - 9/13 period FL / SE.  

 

Beyond there warmer finish to the month as WC ridge moves into the plains with heights along the east coast.

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31 minutes ago, Allsnow said:

Tornado watch for snj 

Surface based CAPE is confined to areas mostly south of 195 in NJ. 

We have no shear, no SBCAPE and perhaps around 1000 J/KG of MUCAPE developing around Sunset. 

Likely storm evolution is elevated in nature with low risk of severe weather IMO.

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15 minutes ago, NJwx85 said:

Surface based CAPE is confined to areas mostly south of 195 in NJ. 

We have no shear, no SBCAPE and perhaps around 1000 J/KG of MUCAPE developing around Sunset. 

Likely storm evolution is elevated in nature with low risk of severe weather IMO.

That’s why the watch is just for snj 

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Temperatures generally ranged from the middle to upper 80s in the Middle Atlantic region. Highs included:

Allentown: 83°
Baltimore: 89°
New York City-JFK: 86°
New York City-LGA: 89°
New York City-NYC: 85°
Newark: 89°
Philadelphia: 87°
Washington, DC: 91°

90° Days for Select Cities (through September 3):

Albany: 13 (2019: 12 days)
Allentown: 24 (2019: 24 days)
Baltimore: 46 (2019: 59 days)
Boston: 14 (2019: 15 days)
Burlington: 20 (2019: 8 days)
Harrisburg: 34 (2019: 33 days)
Hartford: 39 (2019: 27 days)
Islip: 8 (2019: 8 days)
New York City-JFK: 12 (2019: 7 days)
New York City-LGA: 34 (2019: 26 days)
New York City-NYC: 20 (2019: 15 days)
Newark: 31 (2019: 28 days)
Philadelphia: 36 (2019: 35 days)
Scranton: 25 (2019: 12 days)
Washington, DC: 45 (2019: 62 days)

Tomorrow will again see the temperature reach the middle and upper 80s across the region. A few hot spots could reach 90°. Cooler air will return for the weekend as a deep trough will move from Canada toward the Great Lakes Region and into the Northern Plains. The coldest air associated with this trough will likely remain mainly west of the Appalachians. That trough may persist until near or just after mid-month. Nevertheless, the first half of September will likely wind up somewhat warmer than normal.

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 +12.60.

Today, the preliminary Arctic Oscillation (AO) figure was unavailable.

On September 2, the MJO was in Phase 3 at an amplitude of 1.063 (RMM). The September 1-adjusted amplitude was 1.422.

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 September 2, Arctic sea ice extent was 3.861 million square kilometers (JAXA). Based on the August 31 figure, minimum Arctic sea ice extent will most likely finish somewhere from 3.645 million to 3.695 million square kilometers in September. The highest 25% bound is 3.742 million square kilometers. The lowest 25% bound is 3.581 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.

 

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