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October 2014


Rtd208

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I'm worried about the -4 AO in the first week of October. I hope it doesn't lead to early snowfall like 1979. :/

Only problem with a mid October snowfall is many of the trees are still full of leaves and the power companies and towns have still not learned their lessons from the 2011 pre-halloween snowfall and Sandy - so alot of trees are still way to close to power lines and transformers .

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I also noticed that the Euro cooled down quite a bit compared to its previous runs in the medium range. It actually looks like what the GFS was showing days ago when the Euro was trying to pump up a ridge.

yeh , after checking the ensembles . I like the trough stronger in the east with all that blocking .

post-7472-0-45097700-1412516338_thumb.pn

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10 Lowest AO readings for October:

 

1. -5.098, 10/18/2002

2. -4.911, 10/17/2002

3. -4.850, 10/19/2002

4. -4.434, 10/16/2002

5. -4.350, 10/20/2002

6. -3.718, 10/15/2002

7. -3.516, 10/21/2002

8. -3.471, 10/8/1979

9. -3.415, 10/22/2009

10. -3.297, 10/15/2003

 

Good stats there, Don.  With the exception of #8, all of those other winters went on to be exciting ones.

 

Question: Does the length of a major -AO period in October make much difference at all?  I see that the ensembles are seeing a steep drop, generally followed by a quick rebound towards neutral.  I see that the 2002 episode had a bit of staying power, but what about the others?  For example, did 2003 feature a predominantly -AO even if it didn't remain far enough in the tank occupy several top-ten places?

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Can you post a link ? Is it tropical or non - tropical ?

 

It's not tropical. I don't know if the word "big" is appropriate for this either. Noteworthy, perhaps.  It has its origins inland NC at Hour 216 and travels north inland over SE PA at 999 MB at the end of the run. The Ensemble Mean doesn't have it. Someone with more knowledge might chime in to describe why this develops. Trough?  Phasing? Anyway its the tail end of a run, I wouldn't give much thought to it right now.      

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It's not tropical. I don't know if the word "big" is appropriate for this either. Noteworthy, perhaps.  It has its origins inland NC at Hour 216 and travels north inland over SE PA at 999 MB at the end of the run. The Ensemble Mean doesn't have it. Someone with more knowledge might chime in to describe why this develops. Trough?  Phasing? Anyway its the tail end of a run, I wouldn't give much thought to it right now.      

I agree - just something to see if it keeps appearing on the Euro on future runs - and if it starts to show up on other models - what is the best site for viewing the Euro without paying for it ?

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I agree - just something to see if it keeps appearing on the Euro on future runs - and if it starts to show up on other models - what is the best site for viewing the Euro without paying for it ?

 

You can see basic maps on Meteocentre.com. I know French, so I can understand it, but I believe there's an English conversion button. The models are located under the "Previsions" Tab. It's actually a good site for someone like myself who has a nominal interest in this stuff. Although, for 10 bucks a month, this site's model center is a good deal for a little more detailed model info.

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The NAM would indicate a legitimate chance at regional severe weather tomorrow into Wednesday. Even if overdone on moisture return, dynamics and some instability suggest the potential for strong winds in squalls. Low level shear juxtaposed w/ that instability from later Tue into early Wed could support isolated tornadoes.

We will have to see if it's out to lunch. Analogs suggest regional severe weather potential and locally enhanced chances of strong winds.

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The NAM would indicate a legitimate chance at regional severe weather tomorrow into Wednesday. Even if overdone on moisture return, dynamics and some instability suggest the potential for strong winds in squalls. Low level shear juxtaposed w/ that instability from later Tue into early Wed could support isolated tornadoes.

We will have to see if it's out to lunch. Analogs suggest regional severe weather potential and locally enhanced chances of strong winds.

 

12z Rgem has something similar, but it's way out of it's range.

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I'm surprised there isn't more talk about early Wednesday morning. It looks like a rather classic high shear/low CAPE setup. A decent S to SSE fetch in the low levels works on moisture transport. There is good support with the models for a 50-60kt LLJ.

 

About 1/2 of the analogs (12z NAM-based) featured at least 1 severe report in the NYC metro area with about 1/3 of them featuring 1 or more tornadoes.

 

One of the better matches was 10/28/1995 when a tornado hit Staten Island.

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The 18z NAM Bufkit for LGA and JFK has an eml before a 57kt LLJ moves through tomorrow. CAPE approaching 1000> J/kg. EHI numbers between 2-3. One issue is that the best forcing seems to be with the 500mb vort max moving over PA and Upstate NY. That might limit coverage of convection in the NYC metro area.

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