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September 9th-10th Severe Threat


andyhb

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12z NAM has a 985 mb surface low in the UP at 00z Thursday while the 12z GFS has a 997 mb surface low over Lake Huron at the same time. That's one of the bigger differences I can recall inside of 36 hours.

Witt the RGEM also showing 997mb, really have to wonder if the NAM should be tossed. RGEM position is northern tip of lower peninsula.
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...SHORTWAVE TROUGH AND SURFACE LOW LIFTING ACROSS THE

MIDWEST/GREAT LAKES...

...TRAILING COLD FRONT...

PREFERENCE: 00Z ECMWF

CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM CONTINUES TO FAVOR A SLOWER/STRONGER AND MORE NRLY

TRACK WITH THE MID LVL SHORTWAVE AND ASSOCD SFC LOW TRACKING

ACROSS THE MIDWEST/GREAT LAKES AND INTO ERN CANADA OVER THE NEXT

FEW DAYS. THE 12Z GFS OVERALL APPEARS TO BE A LITTLE TOO

PROGRESSIVE AND WEAK WITH THE SYS. THE 00Z ECMWF/00Z GEM AND 00Z

UKMET SPLIT THE DIFF. THE 00Z ECMWF THOUGH IN ITSELF APPEARS A TAD

TOO WEAK. A CONSENSUS SOLN TO ACCOMMODATE THE SPREAD WOULD

ESSENTIALLY FAVOR A BLEND OF THE NON-NCEP MODELS WHICH ARE WELL

SUPPORTED BY THE LATEST GEFS MEAN AND ECENS MEAN...AND SO THIS

WILL BE THE PREFERENCE.

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Don't really agree with this on the new day 1...

 

SOME POTENTIAL WILL EXIST  FOR THE RISK FOR

LOCALLY DMGG WIND AND PERHAPS A COUPLE TORNADOES  

ENEWD INTO NRN IL.  

 

 

 

Yea, not happening.

 

 

Wind probs seem kinda bullish but the wording isn't really overboard imo.  There's some instability that lingers overnight so doesn't seem like a huge stretch that there could be isolated severe reports.

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Current dews are in the low 70's from western MO to sw IA.  I really didn't expect the amount of rain parts of central IL has had already today.  Will be interesting to see which model wins out in this.  IND talking about highs in the 80's for Wednesday. They raise greatest concern about flooding and think the greatest lift will be in northern parts of the CWA with a strong 300 mb jet moving in the evening.

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Flash Flood Watch hoisted for LOT as well...

I merely have experience vs. the wealth of knowledge that most have in here with regard to severe set ups...

But I could see some isolated severe creeping into western portions of LOT...I think incredibly high rain generating storms can create some forward momentum in isolated locals that could lead to faster movement of individual clusters before the jets really start to take over and focus precip and create a larger MCS.

I don't see much in the way of widespread severe action this evening over LOT....but isolated is on the table imo, fwiw, etc...

I shall ooze back into the background before Joe slaps sense into me

:)

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I am surprised by the reduction, especially with the GFS being the fastest model. I am not saying the NAM is going to be correct but using most of the weight on the most progressive model is a bit suspect. Not to mention the GFS is terrible at getting surface thermodynamic profiles correct thus leading to much lower instability.

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They probably could ha e broadrushed 30pct across the area they had 45 before and been fine. I think the reduction was too drastic.

Nope.  It's completely right.  In fact, I would have removed the 30% altogether.  The NAM is too wound up with the low because of convective influences.  Tomorrow is not at all an impressive setup for reasons I mentioned earlier.  There may be a few severe reports, but I'd be shocked if it were anything beyond that.

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Even the RAP doesn't look like it's going to support the wound up NAM.

 

Edit:  well, maybe something in between the NAM and GFS.

 

Bustin' out the RAP to try find a little love for the NAM are we? lol

 

Something between the NAM and GFS may be the way to go.

 

EDIT: Tony, you worry me. I'm looking forward to a legit September threat and you burst my bubble. Seriously, I respect your assessment of the situation that it may not be as big of a threat as originally thought.

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Bustin' out the RAP to try find a little love for the NAM are we? lol

 

Something between the NAM and GFS may be the way to go.

 

EDIT: Tony, you worry me. I'm looking forward to a legit September threat and you burst my bubble. Seriously, I respect your assessment of the situation that it may not be as big of a threat as originally thought.

 

 

I'm concerned about his pessimism as well, as I mentioned earlier. 

 

I was looking at Indiana severe climo and outside of DJF, September is basically the least favorable month.  It has the fewest number of tornadoes other than DJF and it's hard to think of a lot of good events.  9/20/02 comes to mind for obvious reasons.  9/28/99 was decent but fairly localized.

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is it cool to talk heavy rain / MCS action ITT?

 

the new weenie NMM (or whatever its real name is now) paints a massive swath of 2"+ across IA into N IL with many places seeing way more...heavy pwats + ripping LLJ doing work.

 

 

Looks a training situation with that WSW - ENE orientation. About a 1am start time here.

 

hrw-nmm_conus_018_sim_radar.gif

 

hrw-nmm_conus_048_precip_p48.gif

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