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September 2020 wx discussion


forkyfork
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Temperatures rose in the 70s across the region today. Tomorrow will likely be somewhat warmer with more sunshine than today.

In the Rockies, Denver reached 91° today. That surpassed the previous daily record of 89°, which was set in 1992. It was also Denver's 75th 90° or warmer day. The previous annual record was 73 days in 2012.

Temperatures will likely remain at generally above normal levels for the remainder of September. A cool shot is possible to open October.

Phoenix has an implied 91% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of 95.3°-95.5°. That would exceed the previous June-August record of 95.1°, which was set in 2013 and tied in 2015. The existing record is 93.9°, which was set in 2011.

The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.8°C for the week centered around September 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.93°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions have developed and will likely prevail through the remainder of autumn.

The SOI was +14.26.

Today, the preliminary Arctic Oscillation (AO) figure was +0.211.

On September 23, the MJO was in Phase 5 at an amplitude of 1.368 (RMM). The September 22-adjusted amplitude was 1.168.

Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Based on sensitivity analysis applied to the latest guidance, there is an implied 70% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.4°.

 

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A -4sd ao in December during a la nina or near la nina year usually means heavy snowstorm sooner or later...there are exceptions but very few...

12/13/1966 the ao goes below a -4sd...the same time NYC is getting snow and rain but NYC got 7" of snow on 12/24...

12/19/1995 the ao goes below a -4sd...the same time the city is getting an 8" snowstorm...

12/29/2000 the ao goes below a -4sd...NYC got a foot of snow the next day...

12/18/2010 the ao goes below a -5sd...NYC got 20" of snow on 12/26-27...

1950 which is another la nina year had a -4sd ao on the 27th...at the same time NYC was getting 3" of snow and the coldest temp of the winter...9 degrees...not great but it was the best part of that winter...

the two el nino Decembers I found  with a -4sd are...

12/20/1963...ao was below -4sd on the 20th...NYC got 7" of snow on the 23rd...

12/21/2009...ao was almost -6sd...NYC got 11" of snow on the 19th-20th..

four more years I found with an ao -4sd in December...1961 was almost a -4sd...

12/26/1961...almost -4sd...6" of snow on 12/23-24...

12/31/1962...below -4sd...no heavy snow that winter...Just record cold...13 degree max in NYC 12/31/62...

12/27/1968...below -4sd...light snow soon followed...it took till Feb to get a heavy snowstorm...

12/29/1976...below -5sd...light snow that day but the winter had record cold...

12/27/1978...below -4sd...it took till Febfuary to get heavy snow...

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57 minutes ago, uncle W said:

A -4sd ao in December during a la nina or near la nina year usually means heavy snowstorm sooner or later...there are exceptions but very few...

12/13/1966 the ao goes below a -4sd...the same time NYC is getting snow and rain but NYC got 7" of snow on 12/24...

12/19/1995 the ao goes below a -4sd...the same time the city is getting an 8" snowstorm...

12/29/2000 the ao goes below a -4sd...NYC got a foot of snow the next day...

12/18/2010 the ao goes below a -5sd...NYC got 20" of snow on 12/26-27...

1950 which is another la nina year had a -4sd ao on the 27th...at the same time NYC was getting 3" of snow and the coldest temp of the winter...9 degrees...not great but it was the best part of that winter...

the two el nino Decembers I found  with a -4sd are...

12/20/1963...ao was below -4sd on the 20th...NYC got 7" of snow on the 23rd...

12/21/2009...ao was almost -6sd...NYC got 11" of snow on the 19th-20th..

The AO is going lower but our temps are going higher. This is confusing.

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On 9/23/2020 at 11:10 AM, lee59 said:

That is very possible and climate change is one reason why. All I am saying is the best way we can prevent them now, is thru forest management and somehow getting people to be more careful. Just like folks moving to coastal areas and therefore hurricane damage and deaths go up from years ago. Now so many more folks are living in the areas out west that were once not being occupied and therefore much more damage and death, unfortunately. Don't get me wrong, we still have to keep doing what we can to stop polluting our waters, land and atmosphere. I am an optimist on that, I think our energy pollutants of today will become mostly obsolete in the not so distant future as batteries, solar, wind etc. become more widespread.

One thing that's really weird is that both the west and the northeast have been very dry this year.....it isn't just CA and OR that are in severe drought, so is RI......some interesting numbers.....

Medford has gone 100 days without measurable rain in Oregon.

Las Vegas has gone 156 days without measurable rain

Both of the above are records.

Hartford has only had 21 inches of rain so far this year, their 3rd driest on record.

Concord, NH has only had 18 inches of rain so far this year, their 8th driest on record.

 

Meanwhile the Southeast has been consistently flooded out right from the start of the year.

 

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The last 6 days of September are averaging 73degs.     Making it 69degs., or +3.5.

Month to date is  -0.7[68.4].         September should end at 68.5, or near Normal.

With the long range +5 to +8 ( or more) GFS bias, we should be due some lows in the the 40's during the first 10 days of October.

64*(86%RH) here at 6am, heavy haze.    63* at 7am.       T again went nowhere around here, topping out at 74*, now 69*(90%RH)at 8pm.

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17 hours ago, bluewave said:

Looks to max out from 4 to 5 sd around Alaska and also Greenland. 
 

6ADAD814-9A85-4DC5-A5BC-0B7F6F72403A.thumb.png.1aad38dfaa3db832cd0ed0ea8abe254f.png

 

 

Speaking of Greenland, did you see that the WMO finally recognized that -93.3 temp at Klinck, Greenland from 12/22/91 as the coldest ever recorded in the Northern Hemisphere?  Personally I feel that Summit Camp is colder, but they've only kept records for a few years there at the top of the ice cap on Greenland.  It's colder than the coldest parts of Siberia though, but doesn't get anywhere near as warm in the summer.

 

 

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18 minutes ago, LibertyBell said:

Speaking of Greenland, did you see that the WMO finally recognized that -93.3 temp at Klinck, Greenland from 12/22/91 as the coldest ever recorded in the Northern Hemisphere?  Personally I feel that Summit Camp is colder, but they've only kept records for a few years there at the top of the ice cap on Greenland.  It's colder than the coldest parts of Siberia though, but doesn't get anywhere near as warm in the summer.

 

 

Yeah, I saw that. The early 90s were colder times combined with the strong +AO and PV. We actually surpassed those records last JFM. A new paper mentions that the IO standing wave may have contributed. Similar to another paper that I posted last winter. So we need to look to the Indian Ocean for hints on the AO. So some of the long range +AO forecasts for last winter worked out very well. But it verified much stronger than they indicated.

https://www.essoar.org/pdfjs/10.1002/essoar.10503356.1

P

 

Positive SST anomalies in the Indian Ocean have

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8 minutes ago, bluewave said:

Yeah, I saw that. The early 90s were colder times combined with the strong +AO and PV. We actually surpassed those records last JFM. A new paper mentions that the IO standing wave may have contributed. Similar to another paper that I posted last winter. So we need to look to the Indian Ocean for hints on the AO. So some of the long range +AO forecasts for last winter worked out very well. But it verified much stronger than they indicated.

https://www.essoar.org/pdfjs/10.1002/essoar.10503356.1

P

 

Positive SST anomalies in the Indian Ocean have

Chris, I remember there was a streak in 1990 and 1991 where 22 out of 24 months were above normal.  That was just an appetizer for our current climate.....

 

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1 minute ago, LibertyBell said:

Chris, I remember there was a streak in 1990 and 1991 where 22 out of 24 months were above normal.  That was just an appetizer for our current climate.....

 

Montana was one of the few spots not to see as many above normal months.

 

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58/58 here foggy/misty and clouds above the fog.  Looks mostly clouds through early afternoon before we can see some sun around 1PM.  With enough sun it should poke into the upper 70s perhaps low 80s.  Warm again tomorrow and partly to mostly cloudy but little if any rain. 

Sun - Tue with enough sunshine and 850 MB temops >15C will see max temps in mid perhaps an upper 80 in the warm spots but clouds look plentiful with night time lows in the 60s perhaps a 70 spread in between in LGA/JFK / upper 60s NYC/EWR. 

Front comes through at some point Tue (9/29) and Wed (9/30).  Cooler 10/1 - 10/6 but again not likely as cold as this past period 19th - 23rd.  Brunt of cold is west of the region into the Plains, GL and OV down into the Mississippi valley.  A piece of the deeper cool does look to come through Oct 4 - 6th in a moderated fashion.  West cast ridge looks to break down even if for a period by Oct 7th with warmer times in store.  Way beyond does ridge relocate or rebuild in the west?

9/25 - 9/30 : Much warmer than normal mainly drier.  Max temps Sun (9/26) - Tue (9/29).

10/1 - 10/6:   Cooler to much cooler (10/4 - 10/6).  Still think the coldest stays west of the area. Rain chances 10/1-10/2 with reinforced front/ trough moving through.

 

 

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Morning thoughts...

Today will be partly sunny and warm. The temperature will likely top out mainly in the upper 70s with a few lower 80s across the region. Likely high temperatures around the region include:

New York City (Central Park): 78°
Newark: 80°
Philadelphia: 78°

The temperature will likely remain above normal through the remainder of the month.

Yesterday was Las Vegas' 157th consecutive day with no measurable precipitation. That is the longest such stretch on record for that city.

 

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27 minutes ago, Brian5671 said:

Best still west of us as the front gets hung up, but I'll take what I can get it's bone dry here after 2 weeks of sun and low humidity

 

The New England crew is probably happy that this is a rainfall departure and not snowfall.

DF1B2E03-1D23-4304-995A-891DD7FBE390.thumb.png.454425e59d517c9159b16b476150ea78.png

 

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