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July 13-15 storm risk


Kmlwx

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NAM looks like it's closer to the Euro than the GFS.. cold front back in OH at 12z on Tue with a shortwave rounding the low.. probably a quality setup for the day.

 

It looks mighty interesting late Monday too around DC. 

 

00z NAM sounding for IAD at 00z TUES.... decent hodo

 

post-397-0-22214500-1405142040_thumb.png

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Monday from SPC... SLGT risk area =15% due to complexities of the forecast

 

post-397-0-78004100-1405151458_thumb.png

 

 

 


..SYNOPSIS    A TROUGH OF SUBSTANTIAL AMPLITUDE WILL EVOLVE ACROSS THE UPPER MS  VALLEY AND GREAT LAKES REGIONS THROUGH MONDAY WITH THE GREATEST  MID-LEVEL HEIGHT FALLS OF 60-90M PER 12H FORECAST TO SPREAD FROM  MN/WI TO MI/OH/INDIANA DURING THE PERIOD. A STRONG COLD FRONT  ASSOCIATED WITH THE AMPLIFYING TROUGH IS FORECAST TO SPREAD  EAST-SOUTHEAST FROM THE UPPER MIDWEST TO THE MIDDLE MS VALLEY  THROUGH THE PERIOD WITH CYCLOGENESIS POSSIBLE ALONG THE FRONT OVER  THE EASTERN GREAT LAKES...PER LATEST ECMWF. THE FORECAST IS MADE  MORE COMPLEX GIVEN A MORE DIFFUSE FRONT FROM NEW ENGLAND TO THE  MID-ATLANTIC WILL PRECEDE THE STRONGER COLD FRONT...AND THERE ARE  MODEL DIFFERENCES AS TO THE STRENGTH AND TIMING OF CYCLOGENESIS  ALONG THE TRAILING FRONT...AND THE DEGREE OF AIRMASS DESTABILIZATION  THAT WILL TAKE PLACE ALONG/NEAR BOTH BOUNDARIES AND THE DEVELOPING  FRONTAL LOW.    ELSEWHERE...AN EXTENSIVE ZONE OF STORM DEVELOPMENT WILL BE POSSIBLE  AHEAD OF THE FRONT...AND ACROSS THE HIGHER TERRAIN OF THE WEST AND  SOUTHWEST.     ..MID MS VALLEY TO NJ/PA/NY AND NRN DELMARVA AREAS    GIVEN THE AFOREMENTIONED FORECAST COMPLEXITIES ONLY A BROAD ZONE OF  RELATIVELY LOW SEVERE PROBABILITIES CAN BE DEPICTED IN THIS OUTLOOK.  THE LEADING FRONT WILL BE INTERSPERSED WITH CONVECTIVE OUTFLOW...AND  LIKELY ONGOING STORMS...THAT SHOULD SPREAD EAST/NORTHEAST INTO A  CORRIDOR OF INCREASING INSTABILITY. SHEAR AND FORCING AS DEPICTED IN  BOTH NAM AND PARALLEL NAM...AS WELL AS GFS AND ECMWF...WOULD SUPPORT  A FEW TO SEVERAL ORGANIZED STORMS WITH STRONG TO DAMAGING WINDS AND  ALSO SOME TORNADO POTENTIAL.
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Euro shows some pretty big rounds of severe potential til wed... Gfs is done by Monday evening... Quite a disconnect on amplitude and timing for being inside 100 hours....

 

It's typical for the GFS to be too progressive like this.

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DAY 4-8 CONVECTIVE OUTLOOK  

NWS STORM PREDICTION CENTER NORMAN OK  

0359 AM CDT SAT JUL 12 2014  

 

VALID 151200Z - 201200Z  

   

..DISCUSSION  

 

GENERALLY WEAK FLOW AND HIGH HEIGHTS WILL PERSIST ACROSS THE WESTERN  

U.S. WHILE A TROUGH DOMINATES THE EAST...AT LEAST FOR THE FIRST PART  

OF THE MEDIUM-RANGE PERIOD.  

   

..DAY 4  

 

UNUSUALLY LARGE DIFFERENCES APPEAR AT THE START OF THIS FORECAST  

PERIOD BETWEEN DETERMINISTIC VERSIONS OF THE GFS AND EURO WITH THE  

GFS INDICATING 1) FASTER EASTWARD PROGRESSION OF THE STRONG COLD  

FRONT OFF THE EASTERN SEABOARD...AND 2) FASTER DE-AMPLIFICATION OF  

THE LARGE-SCALE TROUGH IN THE EAST. THE EURO ENSEMBLE MEAN APPEARS  

SIMILAR TO THE DETERMINISTIC GFS WITH RESPECT TO SURFACE LOW  

LOCATION IN CENTRAL QUEBEC BUT THE TRAILING COLD FRONT REMAINS  

NEAR/ALONG THE EAST COAST THROUGH MIDDLE OF DAY 4.  

MEANWHILE...DETERMINISTIC UKMET IS A COMPROMISE AND SUGGESTS A  

SURFACE LOW IN SOUTHERN QUEBEC WITH A TRAILING COLD FRONT ALONG THE  

EASTERN SEABOARD AT 00 UTC 16 JULY/TUESDAY EVENING. A MAJORITY OF  

GUIDANCE DOES SUGGEST AT LEAST SOME SEVERE WEATHER POTENTIAL  

CONTINUING AS THE FRONT MOVES TO THE EAST COAST ON DAY 4/TUESDAY.  

HOWEVER...GIVEN THE SPREAD IN SOLUTIONS AT SUCH A RELATIVELY SHORT  

FORECAST RANGE...THE PRUDENT APPROACH IS TO FORECAST PREDICTABILITY  

TOO LOW AT THIS TIME.  

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One thing is very obvious. All of you are very very excited at the prospect of tornadoes with this weather system next week.

 

I hope you get them. I hope it is far worse than the 1974 Superoutbreak. That way you will all be happy. Hell, I'll enjoy the tornadoes with you all, I'll even cheer EF4 tornadoes on.

 

But all I want to know is this: How cool with this cold airmass be next week?

 

Are we talking about highs only around 80 degrees? 75 degrees? 70 degrees?

 

The way I heard people talking about "super cold weather next week" it made me think of high temperatures in the 50s and lows around freezing.

 

I dont want hype. I HATE HYPE.

 

I just want to know how cool will it be next week.

 

I bet we end up with highs around 87 degrees all week with dewpoints around 70 degrees.

 

I can't stand hype. I am sick to death of hype about cold weather in July because I know that is an impossibility. It will NOT be cold next week in northern Virginia. It will be 90 degrees with dewpoints around 70, partly cloudy with a light south wind and a high pressure over the west Atlantic.

 

Cold weather in northern Virginia in mid July is an utter impossibility. It will not happen next week. 

 

It will be warm and humid with a chance of storms each day as is normal.

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I'm not that optimistic about Tuesday right now, GFS/GEFS and SREF's really don't show much on Tuesday. The difference between the GFS/NAM suite and CMC/ECMWF is clear. We just need to see what comes out on top. Monday looks like the best day but timing might be off

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I'm not that optimistic about Tuesday right now, GFS/GEFS and SREF's really don't show much on Tuesday. The difference between the GFS/NAM suite and CMC/ECMWF is clear. We just need to see what comes out on top. Monday looks like the best day but timing might be off

Did something change on the NAM? As of last night it was looking impressive. Also, the SREF is at it's longer ranges right now and I'm not sure I'd put too much stock into it. At this point I'd be most concerned about the GFS holding onto it's solution. 

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Did something change on the NAM? As of last night it was looking impressive. Also, the SREF is at it's longer ranges right now and I'm not sure I'd put too much stock into it. At this point I'd be most concerned about the GFS holding onto it's solution.

12z NAM definitely trended toward the GFS for Tuesday
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Huge step toward Euro on 12z GFS. Tuesday is warm and humid and the Front doesn't really push through until midnight or so

Yeah by Tuesday at H5 the different to 6z GFS is pretty large. Nice round closed low just NE of MI on the 12z as opposed to a messy 552 contour a good bit NE of that on the 6z. 

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Still not a great run but it seems it might be catching on. Positive small steps at least.

I noticed on the Euro run the 500 low goes roughly through the center of MI - is that what we are looking for on the GFS? GFS presently takes it not very deeply into MI on this run. 

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I noticed on the Euro run the 500 low goes roughly through the center of MI - is that what we are looking for on the GFS? GFS presently takes it not very deeply into MI on this run. 

Yeah, basically.. the GFS isn't digging as much initially and then weakens/lifts out quicker. 

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The MON 21z sounding for KIAD from the 12z GFS is decent... but very high PWATs

Monday should be OK.. we'll get storms. But shear is marginal so prob big rainers/microbursts etc. I guess that's standard for us though. Might be a window between like 21-0z for rotating storms as shear picks up but that's always a stretch around here from range.

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