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Oct.-Nov Pattern Discussion


jaxjagman

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Euro is forecasting a very potent ULL to cut off west of Mississippi River this weekend.  It then meanders east for a day or two before taking off quickly NE.  Could be a stormy time early next week for parts of the South.  

 

ecmwf_z500a_sd_eus_9.png

GFS has been showing it,but flattened it out the last couple days.Euro shows 0-6km shear at 50-60kts,control is even higher

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It's certainly shaping up to be the wettest week of the year. I've had 2.65 inches of rain since yesterday with quite a lot to come by next Monday by the look of it.

John the radar has estimates over my neck of the woods to be between 3-4 inches with some spots just south of you at 4 inches. Doesn't surprise me at all with all the rain the past two days. This sure will help toward our deficit and was a big reversal on the dry pattern we have had.

caa63abd106ae4b114b79e4f3cf3ed91.jpg

I'm watching the storms in east KY to see if they will drop down any further southeast. Already have been numerous TOR warnings this afternoon with 1 currently near London,KY.

20b9adabfd4639d79c400feeac4b8b6a.jpg

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GFS has really come in line with the Euro, showing a more amplified pattern.  Monday/Monday could be a particularly stormy day.  Latest runs of the GFS has increased the directional shear along with the trough tilt going negative.  Main mode looks linear though.  Will hammer out the details as it gets closer.  

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Typical high shear low CAPE event.  The GFS would advertise more veering of winds with height across the lower Mississippi River valley and points east.  Also, timing is important, as instability would be a bit higher on the GFS as it has the main system moving through Monday evening into overnight, versus the Euro/CMC which brings the system through Tuesday morning.  Damaging winds looks like the main threat right now...

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The next rainy stretch is starting as the models haven't handled this morning's convection very well. Already have a warning.

post-6441-141286723329.jpg

From MRX:

"THE AREA OF CONVECTION OVER NORTHERN MIDDLE TN THIS MORNING DOES

NOT APPEAR TO BE HANDLED WELL BY ANY OF THE SHORT TERM MODELS.

THESE STORMS APPEAR TO BE DRIVEN BY A MID LEVEL VORT MAX AND SOME

POSITIVE THETA-E ADVECTION. THE 12Z OHX SOUNDING SHOWS GOOD

ELEVATED INSTABILITY...BUT I EXPECT THAT THE ACTIVITY WILL

DIMINISH AS IT ENCOUNTERS A MORE STABLE ENVIRONMENT...SEEN IN THE

12Z RNK SOUNDING. SOME DEVELOPMENT IS EXPECTED IN SOUTHERN AREAS

NEAR A SURFACE BOUNDARY AND WHERE THE AIR MASS IS MORE UNSTABLE AS

SEEN IN THE 12Z FFC SOUNDING. WILL UPDATE TO MAKE SOME SLIGHT

POP/WX ADJUSTMENTS...RAISING POPS MAINLY IN THE NORTHERN PLATEAU"

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Any thoughts on this mountain wave setup for Monday evening?  I don't know enough about what causes these things to tell if this looks mild or more severe.  Math/Met if you're reading this, can you shed some light on the situation?

Never really heard of a mountain wave set up before, so I'll leave that to someone who can answer it better.  Winds at about 5,000 feet and below are expected to be in the 50-60 kt range.  That's pretty strong as it slams into the Apps.  

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Any thoughts on this mountain wave setup for Monday evening?  I don't know enough about what causes these things to tell if this looks mild or more severe.  Math/Met if you're reading this, can you shed some light on the situation?

 

 

If you're in Cosby your best bet is to go up Low Gap and get to the Mt. Cammerer Firetower which is around 5000 ft. That's if you really want to see the winds without driving in it.

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Never really heard of a mountain wave set up before, so I'll leave that to someone who can answer it better. Winds at about 5,000 feet and below are expected to be in the 50-60 kt range. That's pretty strong as it slams into the Apps.

Kory this article from Morristown describes mountain waves pretty good.

http://www.srh.noaa.gov/mrx/?n=mountainwaves

In other words it is when the low level jet is pointed perpendicular to the mountain from the southeast (or northwest for places in North Carolina). When the air flows across the top of the mountains it creates ripple waves that descend down into the foothills. Camp Creek in Greene County, TN is a hotbed for mountain wave activity.

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Any thoughts on this mountain wave setup for Monday evening?  I don't know enough about what causes these things to tell if this looks mild or more severe.  Math/Met if you're reading this, can you shed some light on the situation?

 

Stovepipe,

 

I think this has potential to be a major mountain wave event.  It will likely be a High Wind Watch/Warning type of event.  Looking at the GFS, there will be a strong cross barrier flow over the mountains on Monday night and Tuesday morning, and a powerful LLJ will be approaching the region from the west.  Several key factors are in place for the potential to create some very strong mountain wave winds.

 

I’m not familiar with the local impacts of mountain waves in the Cosby area, so it is difficult to say what the direct impacts will be for you. The strength of mountain wave winds can vary greatly over small distances.  

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If you're in Cosby your best bet is to go up Low Gap and get to the Mt. Cammerer Firetower which is around 5000 ft. That's if you really want to see the winds without driving in it.

 

I may have to do that, thanks for the suggestion.  I've not camped at this place before, but if the winds get too nasty (we'll be in a pop-up camper) we may just have to cut the trip short.  It would be great to experience the wind, just not over night in a flimsy camper with two freaked out little kids.

 

Kory this article from Morristown describes mountain waves pretty good.

http://www.srh.noaa.gov/mrx/?n=mountainwaves

In other words it is when the low level jet is pointed perpendicular to the mountain from the southeast (or northwest for places in North Carolina). When the air flows across the top of the mountains it creates ripple waves that descend down into the foothills. Camp Creek in Greene County, TN is a hotbed for mountain wave activity.

 

That was a good read.  :)

 

Stovepipe,

 

I think this has potential to be a major mountain wave event.  It will likely be a High Wind Watch/Warning type of event.  Looking at the GFS, there will be a strong cross barrier flow over the mountains on Monday night and Tuesday morning, and a powerful LLJ will be approaching the region from the west.  Several key factors are in place for the potential to create some very strong mountain wave winds.

 

I’m not familiar with the local impacts of mountain waves in the Cosby area, so it is difficult to say what the direct impacts will be for you. The strength of mountain wave winds can vary greatly over small distances.  

 

It's always great to get your thoughts when there is a mountain wave threat.  :guitar:

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If enough instability can be managed Monday, look out. Surface low cutting up into the lower Missouri valley 18z Mon-00z Tue. The Euro shows a 60-70kt low-level jet in the modest warm sector with slightly backed surface winds.

Break out of the clouds and if a few discrete cells can fire, there could be significant severe. A lot can change, but the GFS and Euro are coming into better agreement.

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I may have to do that, thanks for the suggestion.  I've not camped at this place before, but if the winds get too nasty (we'll be in a pop-up camper) we may just have to cut the trip short.  It would be great to experience the wind, just not over night in a flimsy camper with two freaked out little kids.

 

Low Gap is pretty steep but once you get to the AT it's not that steep. It's about a 12 mile round trip so it's easily done in a day.

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Wow, November 24, 2001 is now the top analog for this system.  That did hold the record for single day tornadoes until the dreaded April 2011 outbreaks.  Anyway, it appears low level moisture will not be a problem as dew points are expected to near 70 degrees.  CAPE will be higher further south of the Tennessee Valley, but still values of 1,000-1,500 are impressive nonetheless and if the low level lapse rates are high enough, the slightly lower CAPE values wouldn't make a difference.  Shear was never lacking as models are printing out a swath of 40-50 kts effective shear.  It now appears that there will be enough forcing ahead of the system to get discrete cells ahead of the line.  So a check list has all the ingredients for a impressive severe weather outbreak (different than a tornado outbreak).  A potent, organized squall line with embedded bow echos and a few tornadoes are looking likely.  Now it appears pre-squall line convection could also pose a threat.           

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It's looking more like a squall line with few if any discrete cells. The models are also slowing down. The 12z NAM doesn't bring the line through the Mississippi River until mid-afternoon Monday. Still can't rule out a few embedded tornadoes though.

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