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September 2019 General Discussions & Observations Thread


Rtd208
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Newly-released GISS temperature data revealed that summer 2019 was the warmest summer on record globally with a mean temperature anomaly of +0.92°C. The old record was +0.89°C, which was set in 2016. 9 of the 10 warmest summers occurred since 2000 and 5 of the last 10 warmest summers occurred since 2015.

Weekly ENSO data suggest increased prospects of a neutral-cool wintertime ENSO.

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 -5.76 today.

Today, the preliminary Arctic Oscillation (AO) figure was +1.041.

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.

Overall, September remains on a path that will very likely lead to an above normal monthly temperature. A mean figure of 70.0° or above remains possible for New York City.

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°. The latest EPS weekly data shows widespread warmth across the CONUS during October.

On September 15, the MJO was in Phase 8 at an amplitude of 0.906 (RMM). The September 14-adjusted amplitude was 0.707.

Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is approximately 75%.

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3 minutes ago, SnoSki14 said:

Thank you Don for always providing a ton of data analysis for our weather. 

I just wish it wasn't so bleak. Unfortunately all signs point to another very warm fall and possibly winter.

I think our luck has run out. From this moment on its nothing but extreme heat and well AN temps with BN snows. 

Pretty blatant troll post. Do you have anything to back this up?

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5 minutes ago, SnoSki14 said:

Thank you Don for always providing a ton of data analysis for our weather. 

I just wish it wasn't so bleak. Unfortunately all signs point to another very warm fall and possibly winter.

I think our luck has run out. From this moment on its nothing but extreme heat and well AN temps with BN snows. 

All of our winters have been AN temps for the past 50 years. We've had some epic snowstorms. 

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The next 8 days are averaging 71degs., or about 5degs. AN.

Month to date is  +0.3[70.8].         Should be about +1.9[70.9] by the 25th.

No rain for next two weeks.     From hurricane rains to nothing.    Models have a long way to go.

64.2* here at 6am.

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7 hours ago, SnoSki14 said:

Thank you Don for always providing a ton of data analysis for our weather. 

I just wish it wasn't so bleak. Unfortunately all signs point to another very warm fall and possibly winter.

I think our luck has run out. From this moment on its nothing but extreme heat and well AN temps with BN snows. 

A warm fall overall appears to be locked in, but the winter outcome is still uncertain. Some recent developments, if things move in the direction suggested, might lead to a warmer than normal winter, but the time-bound uncertainty is too great to have much confidence right now.

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DC picks up another 2 days of 90 degrees or higher. So they pull ahead of Newark by 32 days which is the highest for the 2010’s. Just goes to show how many times the front has stalled just to the south of our area since the late spring.

90 degree days at DCA and EWR

..........DCA....EWR....difference

2019....57..25....+32

2018....45...36.....+9

2017....43...22....+21

 2016....58...40....+18

2015....52....35....+17

2014...24....15.....+9

2013...35.....25.....+10

2012...53.....33......+20

2011....50.....31.....+19

2010....67.....54......+13

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9 hours ago, SnoSki14 said:

Thank you Don for always providing a ton of data analysis for our weather. 

I just wish it wasn't so bleak. Unfortunately all signs point to another very warm fall and possibly winter.

I think our luck has run out. From this moment on its nothing but extreme heat and well AN temps with BN snows. 

Too early.   I do think the fall and early winter is warm partly due to the +AMO but we'll have to see if the PAC  jet is fast etc and some other indicators before we can lock anything in.

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2 hours ago, Brian5671 said:

Too early.   I do think the fall and early winter is warm partly due to the +AMO but we'll have to see if the PAC  jet is fast etc and some other indicators before we can lock anything in.

One thing I can agree with are warm falls. Above normal water temps and lack of sea ice causing a seasonal lag in the arctic for starters. After that  the arctic will continue to get cold for the foreseeable future with the complete lack of solar insolation. So cold air will be available. It’s just a matter of the local pattern, can we access that cold air or not. I think we are safe as far as snow chances for a while. My thought is more of a boom or bust type of scenario. With some winters still providing epic periods and blockbuster storms. 

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