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September 2021


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It’s always interesting to see how the EPS weeklies compare with the SEAS5 seasonal forecast. The Euro seasonal was picking up on the October blocking potential from the forecast issued back in July. South based blocks can still have above normal temperatures in the Northeast like we saw last winter. So the latitude of the block is important.

Early July forecast for October

383997B7-998D-4A97-A7A1-3F2D083DB7B5.thumb.png.1e24fa82c10703d0cbdd43b2a7a2d367.png

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5 hours ago, bluewave said:

It’s always interesting to see how the EPS weeklies compare with the SEAS5 seasonal forecast. The Euro seasonal was picking up on the October blocking potential from the forecast issued back in July. South based blocks can still have above normal temperatures in the Northeast like we saw last winter. So the latitude of the block is important.

Early July forecast for October

383997B7-998D-4A97-A7A1-3F2D083DB7B5.thumb.png.1e24fa82c10703d0cbdd43b2a7a2d367.png

can we get a sunshine percentage forecast?  I am sick and tired of cloudy days "warm" temperatures or not.  Amount of sunshine is more important for those of us who like to enjoy being outdoors

 

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1 hour ago, LibertyBell said:

looks like highs in the 60s later next week?

40s for lows?

 

The Euro has highs in the 70s and lows in the 50s behind the cold front near the coast later next week. Still has a piece of the WAR hanging on. So the coldest departures remain to our west with the blocking. 
 

3EDF2A5E-9272-47A8-99B5-6D7D33D35DDC.thumb.png.bf9c8a6a3b9eb4cf3a2ae76542ba4e28.png
228CACFA-A796-44B0-A6CD-86DDCC1E4AE1.thumb.png.28f618172e7cffc5760f58b55e829372.png

 

 

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1 hour ago, bluewave said:

The Euro has highs in the 70s and lows in the 50s behind the cold front near the coast later next week. Still has a piece of the WAR hanging on. So the coldest departures remain to our west with the blocking. 
 

3EDF2A5E-9272-47A8-99B5-6D7D33D35DDC.thumb.png.bf9c8a6a3b9eb4cf3a2ae76542ba4e28.png
228CACFA-A796-44B0-A6CD-86DDCC1E4AE1.thumb.png.28f618172e7cffc5760f58b55e829372.png

 

 

Hopefully we’re finally taking steps down in the daily temps. Also hopefully the end of the humidity-early this week was putrid. 

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Tomorrow will be partly sunny and warmer. Readings will likely reach the lower and middle 80s across much of the region. However the warmth will likely be fairly short-lived.

Overnight, the guidance has taken a dramatic turn away from a warm close to September. Instead, early indications of a trough and cooler than normal readings have grown in magnitude. If the guidance holds up, it is close to a toss-up whether 2021 will become the 6th out of the last 7 years during which September has had a mean temperature of 70° or above in New York City. Considering that the close of September is still more than 10 days out, the guidance can still reverse. Prior to 2000, New York City saw such warmth on average once every five years. In short, September has become more an extension of summer than a gateway to autumn in the New York City area.

Fall 2021 will likely be wetter to much wetter than normal in the northern Middle Atlantic region. Since 1869, there have been 9 August cases where New York City picked up 20.00" or more rainfall during the summer. Two thirds of those cases (and 4/5 of those with summer mean temperatures of 73.0° or above) had 17.00" or more fall precipitation in New York City. 2011 is probably the closest match in terms of precipitation and a nearly identical summer mean temperature. Mean fall precipitation for those 9 cases was 14.86". The median was 17.35". The 1991-2020 normal value is 12.27".

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.3°C for the week centered around September 8. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged -0.43°C. Neutral ENSO conditions will likely prevail through September. Afterward, La Niña conditions could begin to develop.

The SOI was +14.50 today.

The preliminary Arctic Oscillation (AO) figure was +0.279 today.

On September 15 the MJO was in Phase 3 at an amplitude of 1.852 (RMM). The September 14-adjusted amplitude was 2.022 (RMM).

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 (1991-2020 normal). September will likely finish with a mean temperature near 70.4° (1.2° above normal).

 

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3 hours ago, bluewave said:

The Euro has highs in the 70s and lows in the 50s behind the cold front near the coast later next week. Still has a piece of the WAR hanging on. So the coldest departures remain to our west with the blocking. 
 

3EDF2A5E-9272-47A8-99B5-6D7D33D35DDC.thumb.png.bf9c8a6a3b9eb4cf3a2ae76542ba4e28.png
228CACFA-A796-44B0-A6CD-86DDCC1E4AE1.thumb.png.28f618172e7cffc5760f58b55e829372.png

 

 

that looks like a pattern where a TC if it was in the western atlantic would come right at us

 

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1 hour ago, donsutherland1 said:

Tomorrow will be partly sunny and warmer. Readings will likely reach the lower and middle 80s across much of the region. However the warmth will likely be fairly short-lived.

Overnight, the guidance has taken a dramatic turn away from a warm close to September. Instead, early indications of a trough and cooler than normal readings have grown in magnitude. If the guidance holds up, it is close to a toss-up whether 2021 will become the 6th out of the last 7 years during which September has had a mean temperature of 70° or above in New York City. Considering that the close of September is still more than 10 days out, the guidance can still reverse. Prior to 2000, New York City saw such warmth on average once every five years. In short, September has become more an extension of summer than a gateway to autumn in the New York City area.

Fall 2021 will likely be wetter to much wetter than normal in the northern Middle Atlantic region. Since 1869, there have been 9 August cases where New York City picked up 20.00" or more rainfall during the summer. Two thirds of those cases (and 4/5 of those with summer mean temperatures of 73.0° or above) had 17.00" or more fall precipitation in New York City. 2011 is probably the closest match in terms of precipitation and a nearly identical summer mean temperature. Mean fall precipitation for those 9 cases was 14.86". The median was 17.35". The 1991-2020 normal value is 12.27".

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.3°C for the week centered around September 8. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged -0.43°C. Neutral ENSO conditions will likely prevail through September. Afterward, La Niña conditions could begin to develop.

The SOI was +14.50 today.

The preliminary Arctic Oscillation (AO) figure was +0.279 today.

On September 15 the MJO was in Phase 3 at an amplitude of 1.852 (RMM). The September 14-adjusted amplitude was 2.022 (RMM).

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 (1991-2020 normal). September will likely finish with a mean temperature near 70.4° (1.2° above normal).

 

what exactly caused this dramatic reversal?  Was it something unforeseen and unforecastable?

 

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2 hours ago, donsutherland1 said:

Larry almost certainly enhanced the blocking. But at this time of year, long-range modeling can change dramatically.

I think Larry is the furthest north a TC has ever made landfall and then it brought snow to Greenland which is amazing.  I think we'll all end up moving north, I have a feeling Greenland is going to turn into a resort and NYC will be underwater by then anyway.

Might not even have to wait that long, looks like people have been leaving NYC in droves even before it goes underwater

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did anyone else notice that the fireflies quit early this year?

i seem to remember a few years back they were swarming well into October due to warm moist weather.  i might've thought they'd do the same this year if you told me the weather ahead of time, but i haven't seen them in several weeks, well back into mid-August.

 

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The next 8 days are averaging 69degs.(62/77), or +1.

Month to date is  72.0[+0.5].        Should be about  71.1[+0.7] by the 26th.

After today, both GFS&Ens. struggle to reach 80 again in the next 15.

Reached 78 here yesterday.     Quick shower at 6:30pm.

82-84 today, p. cloudy, e. wind.

69*(93%RH), hazy sky.       73* at 9am.       78* at Noon.       80* at 2pm.        83* at 3pm.       84* at 3:30pm.        Reached 87* briefly, near 6pm.      80* at 10pm.

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Since September has warmed so much, LGA only has a +1.4 departure  through the 17th.  So the departures don’t tell the whole story. In our warmer climate, +1.4 is all that is needed for a top 10 warmest first 17 days of September. 
 

Time Series Summary for LAGUARDIA AIRPORT, NY
Click column heading to sort ascending, click again to sort descending.
Rank
Ending Date
Mean Avg Temperature Sep 1 to Sep 17
Missing Count
1 1961-09-17 77.4 0
2 2015-09-17 77.2 0
3 2005-09-17 77.1 0
4 1947-09-17 76.7 0
5 2016-09-17 76.0 0
6 2018-09-17 75.3 0
7 1983-09-17 74.9 0
8 1971-09-17 74.7 0
9 2021-09-17 74.4 0
10 1957-09-17 74.3 0
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Morning thoughts…

Today will be partly sunny and warm. High temperatures will likely reach the lower and middle 80s in most of the region.  Likely high temperatures around the region include:

New York City (Central Park): 82°

Newark: 87°

Philadelphia: 86°

Normals:

New York City: 30-Year: 75.5°; 15-Year: 76.4°

Newark: 30-Year: 77.0°; 15-Year: 78.0°

Philadelphia: 30-Year: 78.2°; 15-Year: 79.1°

Tomorrow will be partly sunny and cooler.

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Models really slowing down the cold front later in the week due to the UL closing off over the Great Lakes. So heavy convection potential where the front stalls out. Probably several days of closer to normal temperatures behind the front.

New run

1135CC68-EB53-4014-A50B-205B240E88D2.thumb.png.9c902a35bd31111e0f39dd3127ac628b.png
 

Old run

 

6F3B1AC5-26C8-40C4-B7EB-73841FD9EC1B.thumb.png.a61436fc3668d585daa2a938283c8e53.png

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9 hours ago, Will - Rutgers said:

did anyone else notice that the fireflies quit early this year?

i seem to remember a few years back they were swarming well into October due to warm moist weather.  i might've thought they'd do the same this year if you told me the weather ahead of time, but i haven't seen them in several weeks, well back into mid-August.

 

I saw a handful on September 14th this year, which is the latest here since I started paying close attention about 10 years ago.

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5 hours ago, bluewave said:

Models really slowing down the cold front later in the week due to the UL closing off over the Great Lakes. So heavy convection potential where the front stalls out. Probably several days of closer to normal temperatures behind the front.

12z continues the trend and soaks us

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