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Met Winter 20-21: Pattern Drivers & Evolution


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Tomorrow will be mostly cloudy with some showers, along with cooler temperatures. Following passage of the warm front, Thursday and Friday will be much warmer. Highs in the region will reach the upper 60s and lower 70s Thursday and lower to middle 70s with some upper 70s on Friday. Some showers and even thundershowers are possible, especially on Friday.

 

A sustained period of above to much above normal temperatures is now underway. In general, above normal temperatures will persist through the end of March. Any cool shots will likely be modest and brief. Some of the guidance suggests that a cold shot and at least some snow could affect northern New England near the end of March.

 

The ENSO Region 1+2 anomaly was +0.5°C and the Region 3.4 anomaly was -0.5°C for the week centered around March 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.08°C and the ENSO Region 3.4 anomaly has averaged -0.77°C. La Niña conditions will likely give way to neutral-cool ENSO conditions as the spring progresses.

 

The SOI was +5.41 today.

 

The preliminary Arctic Oscillation (AO) figure was +3.596 today.

 

The 31° temperature recorded at Central Park on March 19 was likely New York City's last freeze of 2020-21 based on a combination of the latest ensemble guidance and the diminishing frequency of April freezes.

 

April freezes have become less frequent in recent years. During the 1991-2020 base period, there were 12 cases where the last freeze occurred in April. The last time the temperature fell to freezing in April occurred in 2018.

 

Select April Statistics:

 

1951-80: Years with freezes: 17; Mean days with lows of 32° or below: 1.1
1961-90: Years with freezes: 17; Mean days with lows of 32° or below: 1.3
1971-00: Years with freezes: 16; Mean days with lows of 32° or below: 1.2
1981-10: Years with freezes: 12; Mean days with lows of 32° or below: 1.0
1991-20: Years with freezes: 12; Mean days with lows of 32° or below: 1.0

 

Least years with freezes: 10, 1984-2013

 

Most years with freezes: 26, 1874-1903, 1880-1909, 1895-1924, 1896-1925, and 1897-1926

 

Lowest number of average days with temperatures of 32° or below: 0.8, 1983-2012, 1984-2013, 1985-2014, and 1986-2015

 

Highest number of average days with temperatures of 32° or below: 3.7, 1871-1900 and 1872-1901

 

Least days in April with temperatures of 32°: 0, Most Recent: 2020

 

Most days in April with temperatures of 32°: 11, Most Recent: 1874   

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 95% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 44.6° (2.1° above normal).

 

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Temperatures topped out in the 50s across the region today as rain moved in. Up north, parts of Quebec saw record high temperatures earlier today. Records included: Quebec City: 59° (old record: 48°, 2000); Rivière-du-Loup: 56° (old record: 46°, 2000); and, Trois-Rivières: 54° (old record: 47°, 2000).

 

Through 8 pm EDT, rainfall totals included:

 

Allentown: 0.80"
Atlantic City: 1.78" (old record: 0.98", 1952)
Baltimore: 1.55" (old record: 1.22", 1989)
Harrisburg: 0.58"
Islip: 0.15"
New York City-JFK: 0.33"
New York City-LGA: 0.76"
New York City-NYC: 0.87"
Newark: 1.01"
Philadelphia: 1.53" (old record: 1.24”, 1989)
Washington, DC: 1.69" (old record: 1.45", 1905)
Wilmington, DE: 1.77" (old record: 1.32", 1989)

 

Rain will move away from the region later tonight. Before then, much of the northern Middle Atlantic and southern New England areas will have seen 0.50"-1.50" rain with locally higher amounts in excess of 2.00".

 

Tomorrow and Friday will be much warmer days. Friday will likely be the warmest day so far this year. Highs in the region will reach the upper 60s and lower 70s tomorrow and lower to middle 70s with some upper 70s on Friday. Some showers and even thundershowers are possible, especially on Friday.

 

In terms of records, daily record high temperatures could be challenged or broken tomorrow across upstate New York, parts of northern New England, and Quebec. Daily records are possible in the Middle Atlantic and southern New England areas on Friday.

 

A sustained period of above to much above normal temperatures remains underway. In general, above normal temperatures will persist through the end of March. Any cool shots will likely be modest and brief. Some of the guidance suggests that a cold shot and at least some snow could affect northern New England near the end of March.

 

April could start out on the cool side. However, historic experience following a warm to very warm March suggests a probability that is skewed toward a warmer than normal April.

 

The ENSO Region 1+2 anomaly was +0.5°C and the Region 3.4 anomaly was -0.5°C for the week centered around March 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.08°C and the ENSO Region 3.4 anomaly has averaged -0.77°C. La Niña conditions will likely give way to neutral-cool ENSO conditions as the spring progresses.

 

The SOI was +7.80 today.

 

The preliminary Arctic Oscillation (AO) figure was +4.278 today. Since 1950, only 1978, 1986, and 2020 saw the AO reach or exceed +4.000 during the March 20-31 period.

The 31° temperature recorded at Central Park on March 19 was likely New York City's last freeze of 2020-21 based on a combination of the latest ensemble guidance and the diminishing frequency of April freezes.

 

April freezes have become less frequent in recent years. During the 1991-2020 base period, there were 12 cases where the last freeze occurred in April. The last time the temperature fell to freezing in April occurred in 2018.

 

Select April Statistics:

 

1951-80: Years with freezes: 17; Mean days with lows of 32° or below: 1.1
1961-90: Years with freezes: 17; Mean days with lows of 32° or below: 1.3
1971-00: Years with freezes: 16; Mean days with lows of 32° or below: 1.2
1981-10: Years with freezes: 12; Mean days with lows of 32° or below: 1.0
1991-20: Years with freezes: 12; Mean days with lows of 32° or below: 1.0

 

Least years with freezes: 10, 1984-2013

 

Most years with freezes: 26, 1874-1903, 1880-1909, 1895-1924, 1896-1925, and 1897-1926

 

Lowest number of average days with temperatures of 32° or below: 0.8, 1983-2012, 1984-2013, 1985-2014, and 1986-2015

 

Highest number of average days with temperatures of 32° or below: 3.7, 1871-1900 and 1872-1901

 

Least days in April with temperatures of 32°: 0, Most Recent: 2020

 

Most days in April with temperatures of 32°: 11, Most Recent: 1874 

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 44.9° (2.4° above normal).

 

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There goes GFS with a super block developing around Apr 01. Other models starting to come on board. Cutoff low literally moves backwards:

gfs_z500a_nhem_fh270-330.gif.50482b067c7066c8717378add3b84854.gif

CMC and Euro don't go out far enough, but they do show the development of the same block around Apr 1. Has some MJO support. If it's correct, we'd have a cool early April. Even flakes would be a possibility, GFS showed some backend flakes in Southern and coastal areas on April 2nd.

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34 minutes ago, Oglem said:

There goes GFS with a super block developing around Apr 01. Other models starting to come on board. Cutoff low literally moves backwards:

gfs_z500a_nhem_fh270-330.gif.50482b067c7066c8717378add3b84854.gif

CMC and Euro don't go out far enough, but they do show the development of the same block around Apr 1. Has some MJO support. If it's correct, we'd have a cool early April. Even flakes would be a possibility, GFS showed some backend flakes in Southern and coastal areas on April 2nd.

Supported by the NAO and AO 

20210325_113526.jpg

20210325_113538.jpg

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Hello there... (Disclaimer: 372 hr op run, very unlikely) 

image.png.a7bb1832adca23c3e2e5f443712df162.png

This shows what that kind of blocking is capable of. Upper level lows are literally moving backwards on GFS. We prob don't see snow because it still takes everything to go just right for april snow, even with blocking, but we'll see what happens, after all the block has only been trending stronger the last few days, has not been backing down. 

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Clouds and fog broke in parts of the region today sending temperatures into the middle and upper 60s. Other parts of the region remained locked in clouds and fog with temperatures being held to near 60°.

 

Where there was sunshine on Long Island, as well as parts of northern New England and Quebec, daily record high temperatures were set. Records included:

 

Burlington: 73° (old record: 68°, 1987 and 1996)
Islip: 67° (old record: 66°, 1987)
Montreal: 69° (old record: 62°, 1996)
Quebec City: 54° (old record: 50°, 2010)
Rivière-du-Loup, QC: 56° (old record: 45°, 2010)
Sherbrooke, QC: 71° (old record: 51°, 2009)
Trois-Rivières, QC: 58° (old record: 52°, 2010)
Westhampton, NY: 66° (old record: 59°, 2017)

 

Tomorrow will likely be the warmest day so far this year. Daily high temperature records could be approached or broken. Highs in the region will reach the lower to middle 70s with some upper 70s in places. Some showers and even thundershowers are possible.

 

A sustained period of above to much above normal temperatures remains underway. In general, above normal temperatures will persist through the end of March. Any cool shots will likely be modest and brief. Some of the guidance suggests that a cold shot and at least some snow could affect northern New England near the end of March.

 

April could start out on the cool side. However, historic experience following a warm to very warm March suggests a probability that is skewed toward a warmer than normal April.

The ENSO Region 1+2 anomaly was +0.5°C and the Region 3.4 anomaly was -0.5°C for the week centered around March 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.08°C and the ENSO Region 3.4 anomaly has averaged -0.77°C. La Niña conditions will likely give way to neutral-cool ENSO conditions as the spring progresses.

 

The SOI was +8.28 today.

 

The preliminary Arctic Oscillation (AO) figure was +4.042 today.

 

On March 23 the MJO was in Phase 2 at an amplitude of 1.484 (RMM). The March 22-adjusted amplitude was 1.277 (RMM).

 

The 31° temperature recorded at Central Park on March 19 was likely New York City's last freeze of 2020-21 based on a combination of the latest ensemble guidance and the diminishing frequency of April freezes. However, some of the recent guidance shows a fairly strong cold shot in early April, so there remains some possibility that the City's last freeze might not have occurred.

 

April freezes have become less frequent in recent years. During the 1991-2020 base period, there were 12 cases where the last freeze occurred in April. The last time the temperature fell to freezing in April occurred in 2018.

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 44.9° (2.4° above normal).

 

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