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September 2020 wx discussion


forkyfork

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52 minutes ago, snowman19 said:

Can’t disagree with that. I do think we will absolutely need the NAO to cooperate this winter. I have a feeling the AO and the PAC side are going to be hostile. You can already see signs of a firehose PAC jet again and we are already dealing with La Niña/-PDO

My over/under for snowfall for NYC this winter is 15 inches.  I dont think we'll see single digits like last season but I dont think we'll get to average either.

 

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1 hour ago, SACRUS said:

Look to go 16 days between measurable precip (as it looks now) Sep 10 - Sep 25/6.  We'll see if the rains can get up here next weekend or is it more towards the 28th/29th.

It will probably be closer to the end of the month.  Whats the record for most days between measurable precip.?

I recall long dry periods happen quite often when there is a lot of action in the tropics that doesn't make landfall- 1995 had this in August and we had widespread wildfires that month.

 

 

 

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11 minutes ago, bluewave said:

The strong IO MJO 1 in October 2011 preceded the 11-12 La Niña winter. There is some research that early IO forcing can excite the PV like we saw last winter.

Any comment  regarding the IOD being totally opposite last year ?  Long range models seem to indicate it goes more so negative as the year ends. Nothing like last year with the extreme positive values in December and continuing into Jan. 

 

 

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On 9/18/2020 at 12:10 PM, SnoSki14 said:

It's complicated and Teddy's evolution will play a role in the future pattern.

Looks like it'll cause the NAO to go negative.

To me it still looks like 80 degrees next weekend. The warm pattern that starts wednesday and goes through next weekend might come to an end a little earlier now though, with that trough swinging in during the early part of the week of the 28th. Hopefully we'll get some decent rain from that too, after this long dry stretch.

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42 minutes ago, winterwx21 said:

To me it still looks like 80 degrees next weekend. The warm pattern that starts wednesday and goes through next weekend might come to an end a little earlier now though, with that trough swinging in during the early part of the week of the 28th. Hopefully we'll get some decent rain from that too, after this long dry stretch.

One things for sure. We won't see weather this cool again til at least the 2nd week of October 

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2 hours ago, frd said:

Any comment  regarding the IOD being totally opposite last year ?  Long range models seem to indicate it goes more so negative as the year ends. Nothing like last year with the extreme positive values in December and continuing into Jan. 

 

 

The relationship that I have been looking at is the October MJO before a La Niña or Niña-like winter. October forcing over the Indian Ocean like last year was followed by less snowfall in NYC. The La Niña winters since 2000 with forcing near the Maritime Continent had better snowfall outcomes  for NYC. 

October composite for a NYC 27.6”to 61.9”seasonal snowfall

9FCDA088-7998-49CC-B408-2E442D8FA8D0.png.67c59761361bc6e23697adc2850ee9ca.png
 

October composite before a NYC 4.8”to 20.5”snowfall season

 

4C386C2F-C9C9-4AB4-BDEE-FE6F2BC7018F.png.71f7d1f6d86840b15d32b1979d0f656b.png

 

 


 

 

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1 hour ago, Stormlover74 said:

One things for sure. We won't see weather this cool again til at least the 2nd week of October 

No question about that. The cooldown for early the week of the 28th doesn't look nearly as cool as what we have right now, and the long range stuff is indicating another warmup in early October. We're gonna be in a mild to warm pattern for quite awhile after tomorrow.

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Looks like smoke is coming back into the NYC forum... Not as thick for the next couple of days but probably a bit noticeable. HRRRX attached predictions for 8PM tonight, 8AM Monday and 8AM Tuesday.  

You can see it on the visible images over the midwest...but the initial revisit of smoke aloft arrives from southeast Canada tonight, then the midwest pall during mid week after theTeddy passage. 

 

Screen Shot 2020-09-20 at 3.10.54 PM.png

Screen_Shot_2020-09-20_at_3_10.04_PM.png

Screen Shot 2020-09-20 at 3.09.00 PM.png

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57 minutes ago, SnoSki14 said:

Models pretty consistent on another big ridge forming out west. Trough axis should be to our west though so could see some heavy rains around that time. 

Perfect time for a homegrown storm too but we never seem to get that on cue.

This would be a good time for something to happen 

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Temperatures rose into the middle 60s across much of the region today despite bright sunshine.

Another cool night lies ahead. Tomorrow morning, Central Park could 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°.

Low temperature estimates include:

Albany: 33°
Allentown: 37°
Boston: 47°
Bridgeport: 48°
Harrisburg: 42°
Hartford: 36°
Islip: 48°
New York City: 49°
Newark: 47°
Philadelphia: 48°
Poughkeepsie: 36°
Providence: 44°
White Plains: 43°

Warmer readings will arrive toward mid-week. Afterward, temperatures will likely remain at above normal levels for much of the remainder of September.

Phoenix has an implied 69% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of 95.1°-95.3°. The existing record is 93.9°, which was set in 2011.

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 +13.73.

Today, the preliminary Arctic Oscillation (AO) figure was +1.521.

On September 19, the MJO was in Phase 4 at an amplitude of 0.915 (RMM). The September 18-adjusted amplitude was 1.284.

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 60% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.4°.

 

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Temperature down to 47 degrees here. Meanwhile in Manhattan (the heat island) the temperature at 7PM was 59 at 8PM 56 and at 9PM it is back up to 58. On nights with very little wind, the range in temperatures can be extreme. My area is reporting temperatures now that range from the mid 40s to low 50s. I have two weather stations in my yard and both normally report very similar temperatures but on nights like this they can be quite different. One is about 5-6 ft. above the ground, as the weather bureau wants, and it says 47.1 and the other which is some 17 ft. above the ground is reporting a temperature of 49.9.

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54 minutes ago, lee59 said:

Temperature down to 47 degrees here. Meanwhile in Manhattan (the heat island) the temperature at 7PM was 59 at 8PM 56 and at 9PM it is back up to 58. On nights with very little wind, the range in temperatures can be extreme. My area is reporting temperatures now that range from the mid 40s to low 50s. I have two weather stations in my yard and both normally report very similar temperatures but on nights like this they can be quite different. One is about 5-6 ft. above the ground, as the weather bureau wants, and it says 47.1 and the other which is some 17 ft. above the ground is reporting a temperature of 49.9.

why is it so damn hard for the city to get below 50 degrees in September?  I have seen it get below 50 in AUGUST.  People need to start ripping out that godawful concrete......

 

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2 hours ago, donsutherland1 said:

Temperatures rose into the middle 60s across much of the region today despite bright sunshine.

Another cool night lies ahead. Tomorrow morning, Central Park could 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°.

Low temperature estimates include:

Albany: 33°
Allentown: 37°
Boston: 47°
Bridgeport: 48°
Harrisburg: 42°
Hartford: 36°
Islip: 48°
New York City: 49°
Newark: 47°
Philadelphia: 48°
Poughkeepsie: 36°
Providence: 44°
White Plains: 43°

Warmer readings will arrive toward mid-week. Afterward, temperatures will likely remain at above normal levels for much of the remainder of September.

Phoenix has an implied 69% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of 95.1°-95.3°. The existing record is 93.9°, which was set in 2011.

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 +13.73.

Today, the preliminary Arctic Oscillation (AO) figure was +1.521.

On September 19, the MJO was in Phase 4 at an amplitude of 0.915 (RMM). The September 18-adjusted amplitude was 1.284.

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 60% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.4°.

 

Weird how difficult it is to get a below normal September....even if we have an above normal rest of the month after Monday, there isn't much left in the month;  October will start in 10 days.

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15 minutes ago, LibertyBell said:

Weird how difficult it is to get a below normal September....even if we have an above normal rest of the month after Monday, there isn't much left in the month;  October will start in 10 days.

In many parts of the U.S., including the New York City area, September has become an extension of summer. 

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