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Thundersnow12

November 11th-12th storm system

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Euro showing 80-85mph winds just off the deck at 900mb over a decent chunk of eastern NE early Wednesday evening.  May be a bit overdone, but extraordinary nonetheless.  Don't think I've ever seen winds that strong at that level before over land.  

 

Agreed, that is off the wall:

 

UGqalAb.jpg

 

I won't bother to post the Eurowx wind charts as there proprietary way of calculating surface winds is bad.

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I won't bother to post the Eurowx wind charts as there proprietary way of calculating surface winds is bad.

 

And what about it is bad? Please do tell.

 

BTW, you shouldn't be posting pay site graphics without permission.

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And what about it is bad? Please do tell.

 

BTW, you shouldn't be posting pay site graphics without permission.

 

For surface winds they just divide the upper level winds by a set number

for gusts, take the sustained wind number x 1.5

 

Also, they allow posting during major events to a certain degree. 

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For surface winds they just divide the upper level winds by a set number

for gusts, take the sustained wind number x 1.5

Also, they allow posting during major events to a certain degree.

10m wind is a variable directly produced by the model...they shouldn't have to do anything to derive it. Gusts may be different I guess...obviously certain situations have a higher gusts to sustained ratio than others.

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For surface winds they just divide the upper level winds by a set number

for gusts, take the sustained wind number x 1.5

 

Also, they allow posting during major events to a certain degree. 

I would probably refrain from posting the graphics unless they are free. Just a heads up.

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The ECMWF people in particular have not taken kindly to their paid maps being posted in the past.  One here and there should be alright, just don't post a bunch.

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Euro showing 80-85mph winds just off the deck at 900mb over a decent chunk of eastern NE early Wednesday evening.  May be a bit overdone, but extraordinary nonetheless.  Don't think I've ever seen winds that strong at that level before over land.  

Using Wunderground.com for the Euro-- I see 28 knot sfc winds in Nebraska. It's about 50-60kt at 850mb (as per College of Dupage). This shows potential for gale force gusts on the cool side to the storm.

 

00z GFS has 30kt at the surface and 40-50kt at 925mb in KS and NE on the cool side of the storm.

 

I was thinking that this thread was mainly concerned about severe weather in the warm sector.

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Text for above day 3

 

  DAY 3 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0232 AM CST MON NOV 09 2015

   VALID 111200Z - 121200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF MO...IL...SW
   IND...WRN KY...NW TN AND NRN AR...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS THE GREAT
   PLAINS...MS VALLEY...OH VALLEY AND TN VALLEY OUTSIDE THE ENHANCED
   RISK AREA...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT
   PLAINS...MS VALLEY...OH VALLEY AND TN VALLEY OUTSIDE THE SLIGHT RISK
   AREA...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ASSOCIATED WITH HAIL AND WIND DAMAGE ARE
   EXPECTED TO DEVELOP IN THE GREAT PLAINS WEDNESDAY MORNING. THE
   SEVERE THREAT SHOULD INCREASE BY AFTERNOON AS THUNDERSTORMS WITH
   WIND DAMAGE AND TORNADOES MOVE QUICKLY EASTWARD ACROSS THE
   MISSISSIPPI VALLEY. THE SEVERE THREAT SHOULD REACH THE OHIO AND
   TENNESSEE VALLEYS BY EVENING.

   ...SRN AND CNTRL PLAINS/MS VALLEY/OH AND TN VALLEYS...
   A VIGOROUS UPPER-LEVEL SYSTEM IS FORECAST TO MOVE QUICKLY EWD ACROSS
   THE GREAT PLAINS ON WEDNESDAY. STRONG DIFFLUENCE...STEEP MID-LEVEL
   LAPSE RATES AND IMPRESSIVE SHEAR PROFILES ASSOCIATED WITH THE EXIT
   REGION OF A 95 TO 110 KT MID-LEVEL JET WILL MAKE CONDITIONS
   FAVORABLE FOR SEVERE THUNDERSTORM DEVELOPMENT WEDNESDAY MORNING FROM
   SE NEB SWD ACROSS ERN KS AND POSSIBLY INTO THE ARKLATEX. LARGE HAIL
   AND WIND DAMAGE WILL BE POSSIBLE ALONG THIS CORRIDOR. AS THE
   UPPER-LEVEL SYSTEM MOVES QUICKLY EWD DURING THE DAY...A COLD FRONT
   WILL ADVANCE RAPIDLY EWD WITH THUNDERSTORMS INCREASING IN COVERAGE
   AND INTENSITY ALONG THE FRONT FROM SRN IA SWD ACROSS WRN MO INTO WRN
   AR.

   ALTHOUGH INSTABILITY AHEAD OF THE FRONT IS FORECAST TO REMAIN
   WEAK...THE FAST EWD MOVEMENT OF THE SYSTEM ALONG WITH VERY STRONG
   LARGE-SCALE ASCENT AND IMPRESSIVE WIND FIELDS SHOULD RESULT IN AN
   ENHANCED WIND DAMAGE THREAT WITH CELLS AND BOWING LINE-SEGMENTS THAT
   DEVELOP ALONG THE FRONT. THE CURRENT THINKING IS THAT A NARROW LINE
   OF STORMS WILL RAPIDLY ORGANIZE AND MOVE QUICKLY EWD INTO THE MS
   VALLEY WEDNESDAY AFTERNOON WHERE A SUBSTANTIAL WIND DAMAGE THREAT IS
   EXPECTED. TORNADOES WILL ALSO BE POSSIBLE WITH THE STRONGER ROTATING
   CELLS EMBEDDED IN THE LINE. THE TORNADO THREAT IS MORE CONDITIONAL
   DUE TO THE MARGINAL QUALITY OF THE MOIST SECTOR.

   AS THE UPPER-LEVEL TROUGH BECOMES NEGATIVELY-TILTED AND THE
   MID-LEVEL JET MOVES INTO THE MID MS VALLEY WEDNESDAY EVENING...A
   WIND DAMAGE THREAT IS EXPECTED TO CONTINUE EWD INTO THE OH AND TN
   VALLEYS. AN ENHANCED WIND DAMAGE THREAT WILL BE POSSIBLE AS FAR EAST
   AS SW IND...WRN KY AND NW TN WEDNESDAY EVENING WITH THE THREAT
   BECOMING ISOLATED DURING THE OVERNIGHT PERIOD. A FEW TORNADOES ARE
   ALSO POSSIBLE DURING THE EVENING.

   ..BROYLES.. 11/09/2015

 

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NAM has, basically, no convection in the ENH. Most "organized" is in C/N Illinois. Then again, it's the NAM. 

The 06z NAM lights up the entire front/dryline all the way to Texas.

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Looking at a bad site.. lol. I now see the entire front lit up. I see Broyles is taking this event for himself? Or, does he do most of the larger "outbreaks"?

No, SPC has a rotating schedule, it just so happens Broyles is working the long term over the last few days. I don't quite buy the extension to the south but everything else is fine with the outlook...

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post-13488-0-93817600-1447062615_thumb.gpost-13488-0-39247900-1447062625_thumb.g

The NAM continues to intrigue me with cellular activity ahead of the main line very late Wednesday evening. I've tried to ignore it the last few runs, but given the favorable shear and marginal lapse rates, I am not sure if we don't get a few surprises further north. Such an anemic warm sector....

Going to be interesting to see how many showers get a blanket warning for 60 MPH winds.

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IWX is extremely worried about damaging showers, I wouldn't be surprised to see a High Wind Warning.

I don't think damaging showers would warrant a high wind warning. I think high wind warnings are for instances where there's no precipitation.

 

SPC has been doing a great job keeping people updated via social media. I see that they posted their severe outlook on Facebook every morning so far. 

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am I seeing things, or does the new 4k NAM want to break out discrete cells all the way up into N. IL?

 

 

You're not seeing things, though these cells are generally out ahead of the sfc instability axis per the model.  There is some MUCAPE though.

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The precip output looks interesting.  Seems like individual supercell tracks.

 

attachicon.gifnam4kmCGP_prec_prec_060.gif

That's interesting.

 

Yeah, 4km NAM isn't that good at this range. It tends to handle precip incorrectly. I'd take it with a grain of salt... or even less than that. The potential is certainly there though... so that solution isn't too unbelievable 

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KC has had some pretty good discussions

 

 


THE FOCUS THEN SHIFTS TO THE DAY TIME HOURS ON WEDNESDAY. MODELS  CONTINUE TO BE IN SOLID AGREEMENT REGARDING TRACK, TIMING, AND  INTENSITY OF THE IMPRESSIVE MID LEVEL NEGATIVELY TILTED TROUGH. AT  THE SURFACE AN EQUALLY AS IMPRESSIVE SURFACE CYCLONE WILL FORM AS  THE SYSTEM EJECTS OUT OF THE ROCKIES AND INTO THE HIGH/CENTRAL  PLAINS. SURFACE WINDS WILL RESPOND WITH SOUTHERLY FLOW AROUND 20  MPH, AND GUSTS PERHAPS REACHING 30 TO 35 MPH AT TIMES. DEPENDING ON  HOW WELL IT MIXES THROUGH THE DAY SEEING AS THOUGH 850 MB WINDS WILL  BE ON THE ORDER OF 60 TO 70 MPH, IT'S CONCEIVABLE THAT EVEN STRONGER  WINDS WILL MIX TO THE SURFACE. FOR NOW, THAT SCENARIO SEEMS UNLIKELY  CONSIDERING THE AMOUNT OF ANTICIPATED CLOUD COVER SHOULD LIMIT THAT  MIXING. WHILE GOOD GULF MOISTURE IS ANTICIPATED TO SURGE NORTHWARD  IN ADVANCE OF THE APPROACHING TROUGH THE DURATION FOR WHICH THE  MOISTURE WILL BE PRESENT IS RATHER LIMITED, WHICH MIGHT PUT THE  QUALITY OF MOISTURE IN SOME QUESTION, AND ULTIMATELY MITIGATE SOME  OF THE INSTABILITY POTENTIAL FOR WEDNESDAY. FURTHER LIMITING  INSTABILITY WOULD BE THE AFOREMENTIONED CLOUD COVER. AT ANY RATE,  NAM CONTINUES TO INSIST ON ML CAPE VALUES APPROACHING 500 TO 1000  J/KG BUILDING INTO THE FORECAST AREA BY LATE MORNING TO EARLY  AFTERNOON. MODELS AGREE ON THE SURFACE CYCLONE PRODUCING A RATHER  TIGHT DRY LINE RUNNING N/S FROM ROUGHLY KFNB SOUTHWARD THROUGH KTOP  AND INTO KTUL BY 18Z WED. THE EXACT PLACEMENT OF THIS SURFACE  BOUNDARY IS STILL TO BE DETERMINED, BUT GIVEN THE AGREEMENT OF THE  MODELS ON PLACEMENT IN EASTERN KANSAS, WILL GO WITH THAT FOR NOW  THEN REFINE. WITH THE DRY LINE VIRTUALLY ON THE DOORSTEP OF THE CWA  BY MID DAY IT WOULD PUT VIRTUALLY ALL OF EASTERN KANSAS AND  WESTERN/CENTRAL MISSOURI AT RISK FOR SEVERE STORMS ON WEDNESDAY.  THIS DRYLINE/PAC FRONT SHOULD BE RATHER PROGRESSIVE AND PUSH THROUGH  THE AREA BY WEDNESDAY EVENING. BUT AS THIS BOUNDARY PROGRESSES  EASTWARD IT WILL LIKELY INITIATE STORMS, WHICH COULD HAVE PLENTY OF  FUEL TO BECOME SEVERE.     AS FOR THE THE PARAMETERS SURROUNDING THIS EVENT...THE TROUGH ITSELF  AND ITS LOW LEVEL FEATURES ARE RATHER IMPRESSIVE. WHILE THE WIND  PROFILE LACKS AN OPTIMAL VEERING-WITH-HEIGHT PATTERN THE SPEED  ASSOCIATED WITH DIFFERENT LEVELS WILL CONTRIBUTE TO DEEP LAYER  SHEAR(0-6 KM) OF AROUND 80 TO 90 KTS. GIVEN PROGGED 850 WINDS  BETWEEN 60 AND 70 KTS AND 500 MB WINDS OF 90 TO 110 KTS THIS AMOUNT  OF SHEAR SEEMS REALISTIC. AREAS OF FAR NORTHERN MISSOURI, WITHIN THE  NE QUAD OF THE SURFACE LOW COULD SEE GOOD TURNING WITH HEIGHT, AS  SURFACE WINDS WILL BE BACKED TO THE SE AND MID LEVEL WINDS WILL BE  OUT OF THE SOUTH. INSTABILITY IS STILL TO BE DETERMINED, AGAIN DUE  TO THE CONCERNS DETAILED ABOVE WITH MOISTURE QUALITY AND CLOUD  COVER. SHOULD THE NAM BE CORRECT WE COULD SEE AREAS ALONG AND SOUTH  OF I-70 TO REACH 500 TO 1000 J/KG OF MLCAPE, WHILE AREAS IN NORTHERN  MISSOURI COULD SEE 1000 TO 1500 J/KG OF MLCAPE. GIVEN THE INCREDIBLE  SHEAR IT'S ACTUALLY POSSIBLE THAT THERE IS TOO MUCH SHEAR FOR THE  LOW INSTABILITY AND STORMS COULD GET SHEARED APART. HOWEVER, WITH  THE HIGHER END OF THE INSTABILITY ENVELOPE, AS IS INDICATED BY THE  NAM THE CAPE/SHEAR RELATIONSHIP WOULD BE CONDUCIVE TO NUMEROUS  SEVERE STORMS ON WEDNESDAY. SHOULD THE INSTABILITY REACH VALUES  CONDUCIVE FOR ORGANIZED STORM FORMATION SUPERCELLS AND LINE SEGMENTS  CAPABLE OF ALL HAZARDS WOULD BE POSSIBLE ON WEDNESDAY. STORM MOTION  WILL BE LUDICROUS, AS HODOGRAPHS PROG STORMS TO BE MOVING TO THE  NORTH/NORTHEAST AT 50 TO 70 MPH. EVEN RIGHT MOVING STORMS WOULD BE  MOVING 50 TO 60 MPH. EVEN THOUGH ALL HAZARDS ARE POSSIBLE WITH ANY  STORMS THAT FORM WED, STRONG WINDS OVER 60 MPH WOULD PROBABLY BE THE  MOST LIKELY HAZARD TO OCCUR. TORNADOES AND HAIL ARE ALSO POSSIBLE,  BUT THE HAIL CONCERNS MIGHT BE MINIMIZED BY THE LACK OF INSTABILITY  AND THE TORNADO CONCERNS WILL HINGE ON MESOSCALE INFLUENCES AND  STORM-SCALE INTERACTIONS.  

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That's interesting.

 

Yeah, 4km NAM isn't that good at this range. It tends to handle precip incorrectly. I'd take it with a grain of salt... or even less than that. The potential is certainly there though... so that solution isn't too unbelievable 

 

...but it will handle and resolve convective/thunderstorm mode better than the other models we can look at. 

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...but it will handle and resolve convective/thunderstorm mode better than the other models we can look at. 

And it has the backing of the 12km NAM with the look of discrete convection. Hell even the GFS in the vv fields at 850 and 700 have the look of discrete storms during the afternoon.

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Always nice to have the storm still strengthening (quite quickly at that) during the event.  Shear vectors are pointing 90 degrees away from the arcing dryline surge.  Very strong vorticity advection.  Can definitely see why the high-res models are keeping things fairly discrete through early evening.  Pretty impressive given such strong forcing.  

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Always nice to have the storm still strengthening (quite quickly at that) during the event.  Shear vectors are pointing 90 degrees away from the arcing dryline surge.  Very strong vorticity advection.  Can definitely see why the high-res models are keeping things fairly discrete through early evening.  Pretty impressive given such strong forcing.  

With the storm strengthening too, the winds will only back more at the surface through the day as it lifts out.

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