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October 2021


Stormlover74
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Morning thoughts…

Today will become partly sunny. It will be unseasonably mild. High temperatures will likely reach the lower and middle 60s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 63°

Newark: 67°

Philadelphia: 66°

Normals:

New York City: 30-Year: 59.2°; 15-Year: 59.4°

Newark: 30-Year: 60.5°; 15-Year: 61.0°

Philadelphia: 30-Year: 61.6°; 15-Year: 61.6°

Cooler air will begin pushing into the region tomorrow.

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Only the 2nd time that Newark made it to 60°every day in October.

 

Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Oct
Click column heading to sort ascending, click again to sort descending.
Rank
Year
Number of Days Max Temperature >= 60 
Missing Count
  1971 31 0
  2021 31 0
- 2017 30 0
- 1994 30 0
- 1984 30 0
- 1947 30 0
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An unseasonably warm October is concluding with an unseasonably warm Halloween Day. October will finish with a mean temperature of 62.0° (4.1° above normal) in New York City.

Numerous locations in the region saw their warmest monthly minimum temperature on record for November. Those locations included:

Atlantic City: 41° (old record: 40°, 2004)
Bangor: 35° (old record: 34°, 1968 and 1989)
Bridgeport: 43° (old record: 41°, 2004)
Harrisburg: 43° (tied record set in 1984)
Islip: 42° (old record: 40°, 1971 and 2017)
Mount Pocono, PA: 35° (old record: 34°, 1920)
New Haven: 42° (old record: 39°, 2014)
New York City-JFK: 47° (old record: 46°, 1971)
New York City-LGA: 49° (old record: 47°, 1971)
New York City-NYC: 47° (old record: 45°, 1946 and 1971)
Newark: 45° (tied record set in 1971)
Philadelphia: 46° (old record: 45°, 1882, 1927 and 1931)
Providence: 41° (old record: 39°, 1971)
Scranton: 38° (old record: 36°, 1971)
Sterling, VA: 39° (old record: 37°, 1971)
Syracuse: 36° (tied record set in 1971)
Washington, DC: 47° (old record: 46°, 1971 and 1984)
Wilmington, DE: 43° (old record: 41°, 1971)

It will turn cooler, but not exceptionally cold, during the first week of November. The duration of the cooler weather remains uncertain. There is an increasing probability that a warming trend could commence during the second week of November. Overall, November will more likely than not average somewhat below normal to near normal in much of the region.

The MJO had completed its passage through Phase 5 at a very high amplitude during the first half of October. During the 1991-2020 period, there were 6 cases with passage through Phase 5 with at least three days at an amplitude of 1.500 or above: 1998, 2000, 2004, 2010, 2017, and 2020. There was a strong signal for the second half of October to wind up warmer than normal (83%) cases in the New York City area. However, that signal broke down to a 50-50 split for the first 10 days of November.

The latest guidance suggests that a period of cooler than normal weather could develop during the first week of November. The big issue concerns the duration of the cooler weather. Recently, Atlantic teleconnections went through an unusual combination for the second half of October where the AO was +0.750 or above and the NAO was -0.750 or below for a record four consecutive days during the second half of October. There were three clusters of cases with one or more such days during the second half of October (1950-2020), two of which favored warmth in the East in November.

Cluster 1 (1961, 1973, 1975): Warm East, Cool West
Cluster 2 (1970, 2006): Warm Northeast/Cool Southeast, Warm West
Cluster 3 (2008): Cool East, Warm West

The October 1-25 North American temperature anomalies most closely resemble those for the Cluster 1 October composite anomalies. The latest CFSv2 monthly forecast favors the Cluster 2 scenario.

As a result, even as La Niña climatology would favor a cool November, more than La Niña is involved. The impact of the rare teleconnections combination suggests the possibility that the month could wind up on the warm side of normal. The evolution of the PNA could be crucial. For both Cluster 1 and 2, the PNA averaged negative during November. For Cluster 3, the PNA averaged above +1.000. For now, this is more theoretical in nature, but it is a plausible scenario.

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". Fall rainfall through October 31 4 pm is 15.29".

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 -0.7°C and the Region 3.4 anomaly was -0.8°C for the week centered around October 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.05°C and the ENSO Region 3.4 anomaly has averaged -0.52°C. La Niña conditions will likely persist through at least mid-winter.

The SOI was -1.48 today.

The preliminary Arctic Oscillation (AO) figure was -0.752 today.

On October 29 the MJO was in Phase 1 at an amplitude of 0.983 (RMM). The October 28-adjusted amplitude was 0.879 (RMM).

 

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On 10/31/2021 at 6:27 PM, donsutherland1 said:

An unseasonably warm October is concluding with an unseasonably warm Halloween Day. October will finish with a mean temperature of 62.0° (4.1° above normal) in New York City.

Numerous locations in the region saw their warmest monthly minimum temperature on record for November. Those locations included:

Atlantic City: 41° (old record: 40°, 2004)
Bangor: 35° (old record: 34°, 1968 and 1989)
Bridgeport: 43° (old record: 41°, 2004)
Harrisburg: 43° (tied record set in 1984)
Islip: 42° (old record: 40°, 1971 and 2017)
Mount Pocono, PA: 35° (old record: 34°, 1920)
New Haven: 42° (old record: 39°, 2014)
New York City-JFK: 47° (old record: 46°, 1971)
New York City-LGA: 49° (old record: 47°, 1971)
New York City-NYC: 47° (old record: 45°, 1946 and 1971)
Newark: 45° (tied record set in 1971)
Philadelphia: 46° (old record: 45°, 1882, 1927 and 1931)
Providence: 41° (old record: 39°, 1971)
Scranton: 38° (old record: 36°, 1971)
Sterling, VA: 39° (old record: 37°, 1971)
Syracuse: 36° (tied record set in 1971)
Washington, DC: 47° (old record: 46°, 1971 and 1984)
Wilmington, DE: 43° (old record: 41°, 1971)

It will turn cooler, but not exceptionally cold, during the first week of November. The duration of the cooler weather remains uncertain. There is an increasing probability that a warming trend could commence during the second week of November. Overall, November will more likely than not average somewhat below normal to near normal in much of the region.

The MJO had completed its passage through Phase 5 at a very high amplitude during the first half of October. During the 1991-2020 period, there were 6 cases with passage through Phase 5 with at least three days at an amplitude of 1.500 or above: 1998, 2000, 2004, 2010, 2017, and 2020. There was a strong signal for the second half of October to wind up warmer than normal (83%) cases in the New York City area. However, that signal broke down to a 50-50 split for the first 10 days of November.

The latest guidance suggests that a period of cooler than normal weather could develop during the first week of November. The big issue concerns the duration of the cooler weather. Recently, Atlantic teleconnections went through an unusual combination for the second half of October where the AO was +0.750 or above and the NAO was -0.750 or below for a record four consecutive days during the second half of October. There were three clusters of cases with one or more such days during the second half of October (1950-2020), two of which favored warmth in the East in November.

Cluster 1 (1961, 1973, 1975): Warm East, Cool West
Cluster 2 (1970, 2006): Warm Northeast/Cool Southeast, Warm West
Cluster 3 (2008): Cool East, Warm West

The October 1-25 North American temperature anomalies most closely resemble those for the Cluster 1 October composite anomalies. The latest CFSv2 monthly forecast favors the Cluster 2 scenario.

As a result, even as La Niña climatology would favor a cool November, more than La Niña is involved. The impact of the rare teleconnections combination suggests the possibility that the month could wind up on the warm side of normal. The evolution of the PNA could be crucial. For both Cluster 1 and 2, the PNA averaged negative during November. For Cluster 3, the PNA averaged above +1.000. For now, this is more theoretical in nature, but it is a plausible scenario.

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". Fall rainfall through October 31 4 pm is 15.29".

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 -0.7°C and the Region 3.4 anomaly was -0.8°C for the week centered around October 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.05°C and the ENSO Region 3.4 anomaly has averaged -0.52°C. La Niña conditions will likely persist through at least mid-winter.

The SOI was -1.48 today.

The preliminary Arctic Oscillation (AO) figure was -0.752 today.

On October 29 the MJO was in Phase 1 at an amplitude of 0.983 (RMM). The October 28-adjusted amplitude was 0.879 (RMM).

 

Thanks for the list, Don!  I believe this will be Mt Poconos latest first freeze on record? And Allentown didn't get below 40 in October?

 

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10 minutes ago, donsutherland1 said:

Yes. It should be MPO’s latest first freeze. Allentown’s low was 36. That’s why it didn’t appear on the list.

wow they actually got almost as cold as MPO, must have been one of those inversion layers that makes the valleys colder.

Will all these locations get their first freeze this week?

I'm guessing the coastal regions and the city will have to wait for around Thanksgiving to have our first freeze?

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