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October 2019 General Discussions & Observations Thread

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Models now trending away from the late October cool down despite a building PNA and -NAO/AO. 

Big cold dump out west struggles to make it here as weak SE ridge builds.

Wouldn't be a terrible pattern for the winter though. 

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2 hours ago, SnoSki14 said:

Models now trending away from the late October cool down despite a building PNA and -NAO/AO. 

Big cold dump out west struggles to make it here as weak SE ridge builds.

Wouldn't be a terrible pattern for the winter though. 

The models have been struggling post super typhoon recurve. Now the new WPAC developments are compounding the errors.
 

 

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2 hours ago, SnoSki14 said:

Models now trending away from the late October cool down despite a building PNA and -NAO/AO. 

Big cold dump out west struggles to make it here as weak SE ridge builds.

Wouldn't be a terrible pattern for the winter though. 

The kind of sustained blocking necessary to lock in a prolonged cold pattern is lacking. Transient blocks won’t cut it, unfortunately. November still appears likely to be warmer than normal. December could be, as well.

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         (accidentally saved under wrong topic earlier today) 

The next 8 days are averaging 57degs., or about 3degs. AN.

Month to date is +2.1[61.0].       Should be +2.4[59.7] by the 27th.

46.5* here at 6am.         60.0* by 3pm    Made it to 61+ before 4pm.

Next 7 days now look to be +5, up from +3 this AM.

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27 minutes ago, donsutherland1 said:

The kind of sustained blocking necessary to lock in a prolonged cold pattern is lacking. Transient blocks won’t cut it, unfortunately. November still appears likely to be warmer than normal. December could be, as well.

transient blocks could bring some snow if its cold enough...

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18z Nams still show rain late day tomorrow.  No other model supports it.  Upton has rain likley 3pm on but I don’t see it unless NAM scores a coup 

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32 minutes ago, uncle W said:

transient blocks could bring some snow if its cold enough...

Yes. I think we will get some shots at snow in December even if the month is warm overall.

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21 minutes ago, Brian5671 said:

18z Nams still show rain late day tomorrow.  No other model supports it.  Upton has rain likley 3pm on but I don’t see it unless NAM scores a coup 

Almost every model has some light rain in the afternoon, but not nearly as heavy as what the NAM indicates. 

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6 minutes ago, purduewx80 said:

Almost every model has some light rain in the afternoon, but not nearly as heavy as what the NAM indicates. 

Yeah, I was just looking at 18z RGEM and it gets some rain up to the north of NYC. Tomorrow afternoon/evening will likely be rainy, even if it's only light rain.

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1 hour ago, uncle W said:

transient blocks could bring some snow if its cold enough...

We just need some help from the Pacific. The -PNA/SE Ridge combo  has been running the table this year.  
 

2019 pattern to date

15C9618E-C6C1-4EA1-AFAC-2F47E4A9573C.gif.4b83b1a1837ad05e2c161adec21f8eda.gif

 

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Milder conditions will gradually return in coming days. Post-Tropical Storm Nestor will likely track rapidly to the east northeast off the Middle Atlantic coast and out to sea. Its rain should pass south of the New York City Metro area later tomorrow and tomorrow night. There is a small chance that a few showers could reach the area. Parts of the Middle Atlantic region including Washington and Baltimore could see a period of rain from Nestor.

The last week of October will likely start mild but end with a cool shot. The cool conditions increasingly appear likely to persist through the first week of November as the Arctic Oscillation goes negative for at least a time.

The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was +0.4°C for the week centered around October 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.88°C and the ENSO Region 3.4 anomaly has averaged +0.12°C. A neutral ENSO is currently the base case for Winter 2019-20.

Since 1981, approximately one out of every seven December cases involved a neutral ENSO. In general, a neutral ENSO in which Region 1+2 had a cold anomaly and Region 3.4 had a warm anomaly (as has been the case in the 6 week moving average) saw a warmer than normal December. Such neutral ENSO cases accounted for about 27% of all neutral ENSO December cases during the 1981-2018 period. This data does not consider blocking, as it is too soon to be confident about that factor in December. However, the greatest warmth coincide with a negative PDO while the coldest outcome coincided with a strongly positive PDO (+1.00 or above for December). Therefore, the first part of winter could start off milder than normal in the Middle Atlantic and southern New England regions.

The SOI was +10.63 today.

Today, the preliminary Arctic Oscillation (AO) figure was -0.989.

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 through November in New York City was 58.9° (59.6° adjusted). All cases featured a warmer than normal fall. There remains a potential for autumn 2019 to rank among the 30 warmest cases on record. For New York City, that would translate into a September-November mean temperature of at least 58.8°.

In August, the AO averaged -0.722 and in September the AO rose to +0.306. The possible transition to predominantly positive values from September into October has been a relatively uncommon occurrence. Since 1950, only 1963 and 2011 saw a transition of an August value of -0.500 or below to positive values in September and a positive average in October. Both cases featured a warmer than normal November in the Middle Atlantic and southern New England areas. Despite what might be a somewhat cooler than normal start to November, a warmer than normal outcome for the month as a whole remains likely.

On October 18, the MJO was in Phase 2 at an amplitude of 1.362 (RMM). The October 17-adjusted amplitude was 1.117.

In the two prior cases when the MJO moved into Phase 1 in late September or early October and then remained in Phase 1 for 12 or more consecutive days as occurred this year, the average decline in the 14-day average temperature for the 2-3 weeks that followed the MJO's moving out of Phase 1 was gradual. The current long-duration Phase 1 episode suggests that the second half of October could be warmer than normal. For New York City, an October mean temperature of 58.5°-59.5° (1.6° to 2.6° above normal) would be implied by those earlier long-duration Phase 1 cases. Based on the sensitivity analysis, the estimated October mean temperature is currently near 59.0°.

Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal October is approximately 78%.

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