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A much colder air mass began moving into the region today. A few locations saw some snow flurries during the late afternoon.

An unseasonably cold weekend lies ahead. There is a small chance that a weak system could bring a period of light snow or flurries to parts of the region late Sunday into Monday. The areas with the highest probability of seeing snowfall are those that are northwest of Newark, New York City, and Bridgeport.

First measurable snowfall statistics for select cities:

Allentown: Normal: December 6; 2020-21: December 9
Bridgeport: Normal: December 3; 2020-21: December 16
Islip: Normal: December 10; 2020-21: December 16
New York City: Normal: December 13; 2020-21: December 16
Newark: Normal: December 9; 2020-21: December 9
Philadelphia: Normal: December 19; 2020-21: December 16

As the ongoing blocking weakens over the next week, temperatures will likely turn milder for at least a time starting during the first week of December. The probability of a relatively mild EPO+/AO+ pattern through at least the first half of December has increased in recent days.

Fall 2021 is well on course to being 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". Fall rainfall through November 26 4 pm is 16.41".

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

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 November 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.67°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +30.98 today.

The preliminary Arctic Oscillation (AO) figure was -0.906 today.

On November 24 the MJO was in Phase 4 at an amplitude of 1.303 (RMM). The November 23-adjusted amplitude was 0.937 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 46.2° (1.8° below normal).

 

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10 hours ago, bluewave said:

That’s not what the raw data says. The minimums and maximum departures have been running lower than the surrounding ASOS sites. NYC has also been running colder than many of the micronet sites. The first freeze in NYC was much closer to the recent average date than areas away from the heat Island. POU had one of their latest first freezes on record. While NYC wasn’t even close to its latest first freeze. 
 

NYC had the lowest temperature on the coldest morning this week for surrounding urban sites

11-24 low temperatures 

EWR…32

NYC…30

LGA….33

Corona….32

Queensbridge….32

East 40th Manhattan….33

Mapped UHI shows Central Park ( or any large park) isn't a great representation of the day to day experience in NYC. Being in an open field instead of directly under a canopy of trees would help some at least.  Manhattan in general looks the coolest on average, at least in the daytime.  Particularly Midtown and Lower Manhattan, thanks to extensive shade from high rises. 

"Using satellite data from the US Geological Survey’s Landsat 8 satellite, the New York City Council’s Data Operations Unit put together a map of how temperature varies across the city..."

https://council.nyc.gov/data/heat/

1365226469_NYCUHI.png.fbe6ca4c73277b54b94f8fa7379ec8ea.png

Matched up with parks highlighted.  Largest NYC parks: Pelham Bay (1st), Greenbelt, SI (2nd), Van Cortlandt (3rd) are the coolest places, as expected.

190794900_NYCUHIPARKS.png.fe1b55b5ebf2e2b4e6295efe2e683c3e.png

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The last 4 days of November are averaging  39(34/44), or -3.

Month to date is  47.6[-1.0].    November should end at  46.5[-1.5].

Reached 50 here yesterday, but that was at Midnite---47 during the daytime.

Today:  40-43, wind nw.-breezy, m. sunny.      First 10 days of December are looking like  37/50 = 43, or +3, att.

36*(55%RH) here at 6am.      37* at 9pm.        38* at Noon.        Reached 40* near 3pm.

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Morning thoughts…

Today will be partly sunny and unseasonably cold. High temperatures will likely reach the lower and middle 40s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 41°

Newark: 44°

Philadelphia: 44°

Normals:

New York City: 30-Year: 50.0°; 15-Year: 50.3°

Newark: 30-Year: 50.7°; 15-Year: 51.1°

Philadelphia: 30-Year: 51.7°; 15-Year: 52.1°

There remains a possibility that parts of the region could see snow showers or even a light snowfall tomorrow. The areas with the highest chance of measurable snow are to the north and west of Newark, New York City, and Bridgeport.

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19 hours ago, bluewave said:

That’s not what the raw data says. The minimums and maximum departures have been running lower than the surrounding ASOS sites. NYC has also been running colder than many of the micronet sites. The first freeze in NYC was much closer to the recent average date than areas away from the heat Island. POU had one of their latest first freezes on record. While NYC wasn’t even close to its latest first freeze. 
 

NYC had the lowest temperature on the coldest morning this week for surrounding urban sites

11-24 low temperatures 

EWR…32

NYC…30

LGA….33

Corona….32

Queensbridge….32

East 40th Manhattan….33

What happened at TEB? 28F. Closer to CPK. Foliage?

And JFK 30F? Warm water mixed with Foliage?

 

You know what the real outlier has been in temperature readings? EWR. A sea of warmth. How many 70 degree readings this year? Many when no one else in the region crossed the threshold.

You know what is another warm outlier? LaGarbage. Their overnight mins are out of whack with the entire region. 

I know why at LGA…I dont know what is going on at EWR. 

But the narrative of LGA and EWR being Gospel and NYC being a throwaway really has gotten out of hand. Especially if we are talking about overnight lows…in late November…with few leaves on the trees and variances of a 28-33 in the immediate area.

 

 

 

 

 

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15 minutes ago, jfklganyc said:

What happened at TEB? 28F. Closer to CPK. Foliage?

And JFK 30F? Warm water mixed with Foliage?

 

You know what the real outlier has been in temperature readings? EWR. A sea of warmth. How many 70 degree readings this year? Many when no one else in the region crossed the threshold.

You know what is another warm outlier? LaGarbage. Their overnight mins are out of whack with the entire region. 

I know why at LGA…I dont know what is going on at EWR. 

But the narrative of LGA and EWR being Gospel and NYC being a throwaway really has gotten out of hand. Especially if we are talking about overnight lows…in late November…with few leaves on the trees and variances of a 28-33 in the immediate area.

 

 

 

 

 

The stations that I posted are closest to the core of the heat island.  Places like JFK and TEB are more on the periphery. My comparison was about the low temperatures within the central areas of the heat island. Not a comparison of low temperatures between the heat island and more suburban or rural areas.

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4 hours ago, jfklganyc said:

What happened at TEB? 28F. Closer to CPK. Foliage?

And JFK 30F? Warm water mixed with Foliage?

 

You know what the real outlier has been in temperature readings? EWR. A sea of warmth. How many 70 degree readings this year? Many when no one else in the region crossed the threshold.

You know what is another warm outlier? LaGarbage. Their overnight mins are out of whack with the entire region. 

I know why at LGA…I dont know what is going on at EWR. 

But the narrative of LGA and EWR being Gospel and NYC being a throwaway really has gotten out of hand. Especially if we are talking about overnight lows…in late November…with few leaves on the trees and variances of a 28-33 in the immediate area.

 

 

 

 

 

both temps at taken at the airport that is why they are higher then anywhere else..

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14 hours ago, dWave said:

Mapped UHI shows Central Park ( or any large park) isn't a great representation of the day to day experience in NYC. Being in an open field instead of directly under a canopy of trees would help some at least.  Manhattan in general looks the coolest on average, at least in the daytime.  Particularly Midtown and Lower Manhattan, thanks to extensive shade from high rises. 

"Using satellite data from the US Geological Survey’s Landsat 8 satellite, the New York City Council’s Data Operations Unit put together a map of how temperature varies across the city..."

https://council.nyc.gov/data/heat/

1365226469_NYCUHI.png.fbe6ca4c73277b54b94f8fa7379ec8ea.png

Matched up with parks highlighted.  Largest NYC parks: Pelham Bay (1st), Greenbelt, SI (2nd), Van Cortlandt (3rd) are the coolest places, as expected.

190794900_NYCUHIPARKS.png.fe1b55b5ebf2e2b4e6295efe2e683c3e.png

Broad Channel looks coolest

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Tomorrow will be another unseasonably cool day. There is a small chance that a weak system could bring a period of snow showers or light snow or flurries to parts of the region tomorrow. The areas with the highest probability of seeing measurable snow are those that are to the northwest of Newark, New York City, and Bridgeport.

First measurable snowfall statistics for select cities:

Allentown: Normal: December 6; 2020-21: December 9
Bridgeport: Normal: December 3; 2020-21: December 16
Islip: Normal: December 10; 2020-21: December 16
New York City: Normal: December 13; 2020-21: December 16
Newark: Normal: December 9; 2020-21: December 9
Philadelphia: Normal: December 19; 2020-21: December 16

As the ongoing blocking weakens over the next week, temperatures will likely turn milder for at least a time starting during the first week of December. The probability of a relatively mild EPO+/AO+ pattern through at least the first half of December has increased in recent days.

Fall 2021 is well on course to being 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". Fall rainfall through November 26 4 pm is 16.41".

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

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 November 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.67°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +20.87 today.

The preliminary Arctic Oscillation (AO) figure was -1.336 today.

On November 25 the MJO was in Phase 4 at an amplitude of 1.171 (RMM). The November 24-adjusted amplitude was 1.308 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 46.2° (1.8° below normal).

 

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20 hours ago, dWave said:

Mapped UHI shows Central Park ( or any large park) isn't a great representation of the day to day experience in NYC. Being in an open field instead of directly under a canopy of trees would help some at least.  Manhattan in general looks the coolest on average, at least in the daytime.  Particularly Midtown and Lower Manhattan, thanks to extensive shade from high rises. 

An open field in Central Park would be a great place to measure temperatures in NYC. Before the new ASOS was installed in the mid 90s, the old sensor was in the open. That’s why the NYC high temperatures were more in line with LGA and EWR up through the 1980s. They let the trees grow over the ASOS and put it in deep shade.  That’s why there is a continuity break in the NYC observations from the days when the sensor wasn’t in the shade. So the highs became cooler relative to EWR and LGA since the 1990s. Central Park was warmer at times than EWR and LGA like during the July 1977 heatwave. So the lower 90 degree counts at the park since the 90s is just an artifact of the ASOS being in deep shade. If they would allow the ASOS to be moved to one of the open fields in Central Park, then you would immediately see an increasing 90 day count closer to EWR and LGA like the old days. 

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The last 3 days of November are averaging  39degs.(34/44), or -3.

Month to date is  47.2[-1.3].       November will end at  46.4[-1.6].

Reached 40 here yesterday.

Today:  42-45, wind w., wet snow ending early, clearing late.      First 10 days of December  35/51 = 43, or +3.

36*(72%RH) here at 6am., wet snow, street wet, cars some white showing.{was 34 a few hours ago}.      39* at 9am.     40* at 10am.          42* at Noon.        45* at 3pm.       47* at 4pm.      42* at 9pm.

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