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September 2020 wx discussion

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The record breaking IO standing wave is making headlines again. Now it looks like it’s producing an early September pattern resembling MJO phase 1. So this translates into the big ridge along the West Coast and trough over the MW/GL. It will limit our early September 90° potential. 
 

BB644C1C-1ECA-4C68-B383-92550522C607.png.e035c45dc79646214cf33b067f3e537a.png
 

B893C2EF-8261-4DCA-8317-2EA2EA644C22.thumb.png.d1588434ef7f26fdf50d4c15e290f458.png

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2 hours ago, bluewave said:

The record breaking IO standing wave is making headlines again. Now it looks like it’s producing an early September pattern resembling MJO phase 1. So this translates into the big ridge along the West Coast and trough over the MW/GL. It will limit our early September 90° potential. 
 


 

 

Where did it stand at this time last year?  Trying to figure out if it’s going to toss a wrench into our upcoming winter’s pattern like it did last year.

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37 minutes ago, Eduardo said:

 

Where did it stand at this time last year?  Trying to figure out if it’s going to toss a wrench into our upcoming winter’s pattern like it did last year.

This year one is seeing an IOD- pattern. Last year one saw among the strongest IOD+ patterns.

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1 hour ago, Eduardo said:

 

Where did it stand at this time last year?  Trying to figure out if it’s going to toss a wrench into our upcoming winter’s pattern like it did last year.

It took until last October for the IO standing wave to emerge with the record +IOD. It continued until mid-December before the record SSTs north of Australia emerged. Then it was off to the races for the record MJO 4-6 which dominated from late December on. There was some research that the IO standing wave being so strong during OND was related to the intense PV which dominated last winter. So it will be interesting so see how the Indian Ocean and Pacific interact this coming fall and winter.

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Wed - Fri much warmer with shot at 90s especially in the warmer spots more likely Thu/ Fri.  Fri transition with strong cold front timing key on highs. 

Labor Day Weekend - another 48 hour cool down  Sat (9/5) and Sun (9/6) half of next (Labor) weekend before warmth builds back in Labor day  (Mon 9/7) as the Western Atlantic Ridge expands west.  Strong trough into the GL / MW with strong ridging along the coast.  Cooler air will likely continue to come on short intervals through mid month with the coolest readings west of the area.  

Way beyond the GL and MW trough looks to move out as western ridging is displaced east by strong trough into the PNW.  Western Atlantic Ridge looks nearby the EC expanding west into the NE / then SE.    Tropics active 9/7 - 9/13

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With such a deep trough into the GL / MW and strong ridging along the coast - you can see a very wet setup perhaps PA/ OH - west of the coast 9/5 - 9/13.  Extent of ridging along the coast will determine how much cool and penetrate and what duration.  Right now looks a bit back and forth bias warm with ridging encompassing the coast and WAR typically stronger than modeled this season.

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17 minutes ago, SACRUS said:

With such a deep trough into the GL / MW and strong ridging along the coast - you can see a very wet setup perhaps PA/ OH - west of the coast 9/5 - 9/13.  Extent of ridging along the coast will determine how much cool and penetrate and what duration.  Right now looks a bit back and forth bias warm with ridging encompassing the coast and WAR typically stronger than modeled this season.

I do think the WAR will be under modeled & there’s a nice corridor for the east coast to be at risk for any tropical systems.  Hopefully I’m wrong on this for other reasons.

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1 hour ago, SACRUS said:

With such a deep trough into the GL / MW and strong ridging along the coast - you can see a very wet setup perhaps PA/ OH - west of the coast 9/5 - 9/13.  Extent of ridging along the coast will determine how much cool and penetrate and what duration.  Right now looks a bit back and forth bias warm with ridging encompassing the coast and WAR typically stronger than modeled this season.

ecmwf-ens_z500a_atl_11.png

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Saw the several posts today on the longer range: I agree... looks interesting.  Adding the NAEFS D8-14...  thats' been consistent for a couple of days now... how it evolves is unknown (pieces for northern stream, or maybe cutoff something down in TN?)  What this flags for me is a southerly component and potential for increased rainfall.  Maybe most of it will be Apps west?  I'll guess maybe a little closer to normal for most of our area, than what we've experienced since Isaias. This outlook would be for September  - week two. 

 

Screen Shot 2020-08-30 at 8.48.31 AM.png

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13 hours ago, bluewave said:

The record breaking IO standing wave is making headlines again. Now it looks like it’s producing an early September pattern resembling MJO phase 1. So this translates into the big ridge along the West Coast and trough over the MW/GL. It will limit our early September 90° potential. 
 

BB644C1C-1ECA-4C68-B383-92550522C607.png.e035c45dc79646214cf33b067f3e537a.png
 

B893C2EF-8261-4DCA-8317-2EA2EA644C22.thumb.png.d1588434ef7f26fdf50d4c15e290f458.png

do you also see very limited east coast TC landfall potential?  at the very least, it's not as favorable as it was earlier in the summer....it looks to me to be a pattern where systems will pass to our south and hit Fla or enter the Gulf or recurve out to sea.  Perhaps later in September (after the 20th) and into October will enter another hazardous period.

 

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14 hours ago, LibertyBell said:

do you also see very limited east coast TC landfall potential?  at the very least, it's not as favorable as it was earlier in the summer....it looks to me to be a pattern where systems will pass to our south and hit Fla or enter the Gulf or recurve out to sea.  Perhaps later in September (after the 20th) and into October will enter another hazardous period.

 

It looks like we will have a trough in the Great Lakes and Midwest at least into early September. There should also be plenty of high pressure to our north and east with onshore flow here. But we will just have to wait and see how  many of the AEWs coming off Africa can actually develop into named systems.

36947F9E-0A95-468C-AEEF-9033371F9682.thumb.png.0b7f59d02cca80d999e72c033672857d.png

 

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The first 10 days of September are averaging 76.5degs., or 5degs. AN.

Feel free to subtract 5 degrees from this GFS average, and just call the first 10 days Normal.

Sept. 08---14 seems real wet.

September/October appear trendless.    We start off at 5820m on the 500mb heights and maybe the upcoming week looks AN.      The only other deviating week would be: Week 3 of October, which is BN.       The 5820m at that time is down to Cuba.

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Warm up Wed (9/2) - Friday (9/4)  with off chance of 90s in the warmer spots especially Thu and Fri before the front.  Labor Day weekend looking like a gem with highs near 80 Sat (9/5) and Sunday (9/6)  and warming up Mon (Labor Day 9/7)  into the mid 80s.    

Beyond Labor day 9/8 - 9/14  WC ridge with trugh into Gl / MW and the Western Atlantic ridge expanding wet along the east coast.  Back and forth intrusions of cooler day or two followed by return humid/warm flow.  Looks like a block of fronts and lows west of the area into PA/ OH could see large rain amounts in the period.  Should see WC ridging breakdown a bit and push into the plains later the second half of Sep and subsequent EC heights and warm period.

 

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September Preview:

In the New York City area, September has increasingly become an extension of summer. Prior to 2000, a monthly mean temperature of 70° or above was relatively uncommon. Prior to 1950, Central Park saw such warmth about once every 5.4 years. From 1950-1999 (during which New York City has had a mature urban footprint), such warmth was recorded approximately once every 4.5 years.

Since 2000, 70° Septembers have occurred about once every 2.0 years. There have been 10 such Septembers during the 2000-2019 period, which is just below the figure of 11 recorded during 1950-1999. Since 2010, New York City has had 7 cases where September had a mean temperature of 70° or above, including the last four years.

During the last 30 years, September has had a mean temperature of 69.0°, which is the warmest 30-year period on record for September. During the last 10 years, September has had a mean temperature of 70.5°, which is the warmest 10-year period on record for that month. Records go back to 1869. The 1981-2010 normal temperature for September is 68.0°.

New York City's 30-Year Moving Averages for September:

30-Year Period ending:
1990: 68.1°
2000: 68.1°
2010: 68.4°
2019: 69.0°

September 2020:

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°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September. The first half of September will likely see a deep trough located over the Great Lakes to Central Canada. However, the Western Atlantic Ridge could blunt the amount of cool air that reaches the New York City area. Afterward, that trough could dissipate. Overall, September will likely wind up with a mean temperature near 70° or about 2° above normal in New York City.

 

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On 8/30/2020 at 10:26 AM, donsutherland1 said:

This year one is seeing an IOD- pattern. Last year one saw among the strongest IOD+ patterns.

 

On 8/30/2020 at 10:56 AM, bluewave said:

It took until last October for the IO standing wave to emerge with the record +IOD. It continued until mid-December before the record SSTs north of Australia emerged. Then it was off to the races for the record MJO 4-6 which dominated from late December on. There was some research that the IO standing wave being so strong during OND was related to the intense PV which dominated last winter. So it will be interesting so see how the Indian Ocean and Pacific interact this coming fall and winter.

Are either of you able or willing to speculate what significance (if any) an opposite IOD state at this time might hold for this coming fall and winter?

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once again the nam/euro gave us way too much rain from a weak low. the 1" amounts for tuesday have vanished

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33 minutes ago, forkyfork said:

once again the nam/euro gave us way too much rain from a weak low. the 1" amounts for tuesday have vanished

I fully expect them to give us plenty of fantasy snow this winter as well. 

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I wonder what the 500MB height record is for Newfoundland in September? All the models are going near 600 DM In about 10 days. 

E7255F88-246E-42F8-99F1-00686F5B44DD.thumb.png.f51fcc9faa520eda15ba846cb0c3b483.png

6BB26725-4BD0-4133-81C5-818D1F642A7D.thumb.png.810708aa70138ff2a64b39b33415c506.png

 

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1 hour ago, bluewave said:

I wonder what the 500MB height record is for Newfoundland in September? All the models are going near 600 DM In about 10 days. 

I like to know that as well,  and once determined,  I would find it interesting to see what, if any , correlation there is to a later Fall and early winter NAO signal or tendency because of this potential event, with the disclaimer, there may be zero relationship.   

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9 hours ago, Eduardo said:

 

Are either of you able or willing to speculate what significance (if any) an opposite IOD state at this time might hold for this coming fall and winter?

The IOD state at this time of year doesn’t seem to have much influence. During the winter, and IOD- has often seen an increased tendency for the MJO to reside in the Maritime Continent phases (Phases 4 and 5).

 

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August ended at +1.7[76.9].

The first 8 days of September are averaging 77degs., or 5degs. AN.      Or if you prefer, just Normal.

Holiday Weekend OK except for Labor Day itself.   lol.

Sept. 8 ---14 still looks real wet.

68*(94%RH), overcast, streets wet.         80*(72%RH) by 3:30pm with more sun than predicted the last 90mins.

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Modeling via the ensembles continues to suggest next week (7-14), will provide us near normal qpf, maybe above normal interior a below eastern LI?   Several events and somewhat depends on position of a possible quasi-stationary front the eastern seaboard.  This as per several graphics posted from various members the past two days. One thing that from my perspective will be less evident than in summer... heavy convection, due to shorter-cooler days.  So, I think we're going to need a boundary to help us out, aside from the upslope interior mountain ridges. If it ends up the flow is southerly, rather than southeasterly, then we have more opportunity for LI/CT to see some decent showers from the lift of the southerly flow over the landmass.  Lots of unknowns.

Regarding the SPC depicted D3 marginal severe for our area this Thursday... holding off as a topic at this time.  It is late in the season, and the EC does not have enough CAPE-KI, in my opinion,  til evening.  The winds aloft - modeled and discussed by SPC will be in place,  but the CAPE-KI are slower to arrive in our forum than the 06z/1 GFS models. 

Otherwise...seems like periods of showers-drizzle the next two days (today-Wednesday). 657A/1

 

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Morning thoughts...

Overnight, showers brought 0.12" rain to New York City and Newark. Those showers are now departing from the region. The remainder of today will be partly to mostly cloudy. There could still be another shower. Temperatures will be in the 70s across much of the area except near or just above 80° in southern New Jersey southward. Likely high temperatures around the region include:

New York City (Central Park): 76°
Newark: 79°
Philadelphia: 81°

Temperatures will likely return to above normal levels near or just after mid-week. Afterward, a deep trough in Canada will move toward the Great Lakes Region and provide a period of somewhat cooler weather. That trough may persist until near mid-September.

Phoenix, which just experienced its hottest summer, by far, could see a new period of excessive heat develop late this week.

 

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11 hours ago, donsutherland1 said:

The IOD state at this time of year doesn’t seem to have much influence. During the winter, and IOD- has often seen an increased tendency for the MJO to reside in the Maritime Continent phases (Phases 4 and 5).

 

Yes we learned this hard lesson last year.  Is there any evidence that the converse produces a better result for us (i.e., a tendency for the MJO to hang around in the colder phases)?

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8 minutes ago, Eduardo said:

Yes we learned this hard lesson last year.  Is there any evidence that the converse produces a better result for us (i.e., a tendency for the MJO to hang around in the colder phases)?

When the IOD is positive, the MJO is often in more favorable phases. However, long-term changes in sea surface temperatures are promoting an increased tendency for the MJO to reside in the Maritime Continent.

Here's a paper @bluewave posted on this topic: https://www.nature.com/articles/s41586-019-1764-4

 

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