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September 2019 General Discussions & Observations Thread


Rtd208
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52 minutes ago, NYCweatherNOW said:

The latest computer models lowered the heat probabilities for late September and early October for our area getting any 90’s. It’ll be above average nonetheless. Enjoy the most perfect weather for the next few days at least. Currently 72 at 10am with low 52 humidity going up to 82 degrees or so.

only a fool would believe in october we would have 90's in nyc...

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5 minutes ago, bluewave said:

Obviously, the MJO 1 has a much different 500 mb pattern now than in the winter. But this could  be one of the stronger phase 1’s we have seen in late September or early October. Maybe related to the very positive IOD. We also don’t usually see such a strong -NAO and SE Ridge together this time of year. So it looks like quite a battle setting up between the two. It’s possible  the highest warm departures find a way to miss to our south and west. But it wouldn’t take much for that SE Ridge to push some of the stronger heat our way.

Do you think any of these events can be clues of the upcoming Fall season and early winter?

Raindance posted in the Nino thread, that a deep -SOI now can lead to possibly cold Decembers.  

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46 minutes ago, frd said:

Do you think any of these events can be clues of the upcoming Fall season and early winter?

Raindance posted in the Nino thread, that a deep -SOI now can lead to possibly cold Decembers.  

It’s tough to say which one of these many competing factors will win out for the winter.

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Under brilliant sunshine, temperatures rose generally into the middle 80s across the Middle Atlantic region. Baltimore, Richmond, and Sterling reached 90°. Another very warm day lies ahead for tomorrow.

Courtesy of low sea ice, abnormal warmth prevails in northern Alaska. There is an implied 84% probability that Utqiagvik will record its warmest September on record. It is possible that Utqiagvik could register its first 40° mean temperature for September. The existing monthly record of 37.7° has stood since 1998.

The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -0.3°C for the week centered around September 11. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.65°C and the ENSO Region 3.4 anomaly has averaged -0.03°C. There remains uncertainty about the ENSO evolution later this fall. Despite the guidance, the strong cooling in Region 1+2 indicates that the prospects for a neutral-cool ENSO during the winter have increased. Such a scenario may be somewhat more likely than not. That outcome could have significant winter season implications.

Since 1991 when weekly ENSO region data was available, six years have seen September record 2 or more weeks with -1.0°C or cooler weekly anomalies in Region 1+2: 1996, 1999, 2002, 2007, 2010, and 2017. 5/6 (83%) of those cases went on to feature warm December-February temperature anomalies in the Middle Atlantic and southern New England regions. 2002 had one such week ahead of what would evolve into an El Niño winter.

The SOI was -19.49 today.

On September 19, the SOI fell to -35.30. Often an SOI figure at or below -30.00 during the second half of September has been followed by a warmer than normal October. 2002, which saw severe October blocking during which the Arctic Oscillation fell to as low as -5.098 on October 18, was an exception.

Today, the preliminary Arctic Oscillation (AO) figure was +0.481.

Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall.

Among those five cases, 2015 made a transition from predominantly negative AO values to predominantly positive ones during the fall. The combination of the AO's recent increase to the strongest positive values since April and some of the extended range guidance leave open a scenario where the AO is currently in the early stages of evolving to a predominantly positive regime. Such an outcome would also favor a warmer than normal fall and possible warm start to winter in the Middle Atlantic and southern New England regions. For now, this is merely a hypothetical discussion of one potential path toward winter. Many other variables are involved. The only idea that carries weight at this time is that the possible evolution reaffirms the longstanding signal for a warm fall.

The latest EPS weeklies favor persistent ridging and warm anomalies in the East during October. The latest CFSv2 forecast for October also shows warm anomalies across much of the CONUS.

Therefore, a warmer than normal September and fall appear likely. The potential for autumn 2019 to rank among the 30 warmest cases on record remains on the table. For New York City, that would translate into a September-November mean temperature of 58.8°.

On September 20, the MJO was in Phase 8 at an amplitude of 1.377 (RMM). The September 19-adjusted amplitude was 1.610.

Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is approximately 86% and the probability of a monthly mean temperature of 70.0° or above is 53%.

 

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4 hours ago, tdp146 said:

What a beautiful day on the beach. Swell from Humberto is dropping now, but great rides early today and honestly just beautiful to sit on the sand and watch it roll in for hours. 

Amazingly Humberto caused more beach erosion and washovers then Dorian. This is due to swell periods being significantly higher (16 vs 12 seconds) which contain much more energy. Yesterday at Jones Beach I surfed some of the biggest waves since Bill. Easily some 12 foot sets. Today was smaller in the 8 foot range on the bigger sets. Most interesting to me was the refraction occurring off the Hudson Canyon yesterday which led to waves moving in from the west!!!!! 

And, please please rain!

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2 hours ago, LongBeachSurfFreak said:

Amazingly Humberto caused more beach erosion and washovers then Dorian. This is due to swell periods being significantly higher (16 vs 12 seconds) which contain much more energy. Yesterday at Jones Beach I surfed some of the biggest waves since Bill. Easily some 12 foot sets. Today was smaller in the 8 foot range on the bigger sets. Most interesting to me was the refraction occurring off the Hudson Canyon yesterday which led to waves moving in from the west!!!!! 

And, please please rain!

Refraction off the Hudson canyon. You gotta explain. 

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Next 8 days are averaging 72degs., which is about 8degs. AN now.

Month to date is  +0.1[69.8].        Should be +2.3[70.4] by the 30th.

66.9* here at 6am.      68.0* by 8am.  70.3* by 10am.    72.6* by Noon.

EURO says we (Central Park) will average a high of 82* over the next 10 days, or +10 to +12.     GFS too high to mention.

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