June 3rd/4th severe weather possibilities.

Toot wrote:12z St Louis WRF has a 996Mb surface low centered near the central Illinois/Missouri border at hr 84. Once again im going to note the close resemblance of track and strength (Not exactly alike but similar) to that of the early march system. The temperature profiles of the low's warm and cold sector's are also very similar.

One can clearly see the warm and cold front boundaries on this graphic as their related convection is clearly visible. I expect something similar to the early march system to transpire. There may be some discrete cells out ahead of the main line of convection (cold front) and these will be the troublemakers if they are indeed the case. It will be an interesting system to watch unfold



2m temps


Looks like this system will be dynamic enough to clear out warm front convection enough for the atmosphere to destabilize again before the second round comes thru. That would mean severe along both boundaries...the warm front and cold front as the system marches eastward.

Adam2014 wrote:Also toot, where did you get that weather graphic at I know it is from Noaa but I couldn't find it on the NAM. Who ever is in between the cold front and warm front will have the best chance at seeing tornadoes. That is where the best shear is and the best instability. On the models, it looks like the Tennessee and parts of the Ohio Valley are under the gun. That will change some but right now we could have a severe weather outbreak out our hands.

tennessee storm09 wrote:latest afternoon update from megs afd, is now mentioning the tornado word, all depends on exact track of the surface lp... interesting

WEDNESDAY NIGHT THROUGH FRIDAY...THIS PERIOD IS LOOKING MORE
INTERESTING. 12Z MODELS HAVE COME INTO DECENT AGREEMENT CONCERNING THIS PERIOD. A COUPLE POTENT PIECES OF MID LEVEL ENERGY WILL MOVE INTO THE CENTRAL PLAINS WEDNESDAY NIGHT HELPING TO DEVELOP A SURFACE LOW PRESSURE SYSTEM OVER NE OKLAHOMA/NW ARKANSAS BY 12Z THURSDAY. MEANWHILE THE STALLED FRONT OVER THE MIDSOUTH WILL BEGIN TO LIFT BACK NORTH AS A WARM FRONT. THE UPPER LEVEL ENERGY OVER THE CENTER OF THE U.S. WILL CONSOLIDATE INTO A POTENT UPPER LOW BY THURSDAY AFTERNOON. THE SURFACE LOW WILL STRENGTHEN AS IT MOVES INTO INTO SE MISSOURI THURSDAY AFTERNOON AND THEN OHIO VALLEY THURSDAY EVENING WITH A COLD FRONT SWEEPING ACROSS THE MIDSOUTH.

RIGHT NOW IT LOOKS LIKE THE INGREDIENTS WILL BE IN PLACE FOR AT LEAST SOME SEVERE WEATHER. WARM AND MOIST LOW LEVELS COMBINED WITH COOLING MID LEVEL TEMPS WILL CREATE PLENTY OF INSTABILITY. BY THURSDAY AFTERNOON LIFTED INDEX VALUES COULD APPROACH -6C TO -8C WITH SBCAPES APPROACHING 2000 J/KG. WIND FIELDS ALOFT ARE NOT TREMENDOUS BUT THEY SHOULD BE ADEQUATE FOR STORM ORGANIZATION. A 850 MB LOW LEVEL JET OF ABOUT 30 KTS PUSHES INTO THE AREA IN ADVANCE OF THE SURFACE FRONT WHILE A 45 KT MID LEVEL JET PUNCHES INTO THE REGION. THE SURFACE LOW WILL ALSO BACK THE SURFACE WINDS ACROSS THE AREA HELPING TO CREATE 0-3KM HELICITY VALUES ABOVE 15O M2/S2. THERE ARE SOME NEGATIVES TO LOOK AT AS WELL. MODELS ARE HINTING THAT A MCS COULD DEVELOP ALONG THE WARM FRONT WEDNESDAY NIGHT AND SLIDE INTO THE AREA EARLY THURSDAY WHICH COULD COMPLICATE MATTERS. A LOT ALSO DEPENDS ON THE EXACT TRACK OF THE SURFACE LOW. FOR NOW WILL GO WITH SHOWERS AND THUNDERSTORMS BECOMING LIKELY WEDNESDAY NIGHT INTO THURSDAY WITH SOME SEVERE STORMS POSSIBLE. MOST LIKELY THREATS ARE DAMAGING WINDS AND HAIL THOUGH THE CURRENT FORECAST TRACK OF THE SURFACE LOW SUGGESTS THAT THERE IS AT LEAST SOME THREAT FOR TORNADOES. THE COLD FRONT WILL PUSH EAST OF THE AREA BY 12Z FRIDAY WHICH WILL PUT AN END TO PRECIP CHANCES AND THE THREAT OF SEVERE WEATHER. FRIDAY WILL BE MUCH COOLER WITH AT LEAST SOME CLEARING SKIES AND PERHAPS SOME WRAP AROUND STRATOCU UP NORTH.

Toot wrote:

tennessee storm09 wrote:latest afternoon update from megs afd, is now mentioning the tornado word, all depends on exact track of the surface lp... interesting

Excellent discussion too..im gonna post it

By Thursday, the upper level pattern is expected to amplify quickly as a strong upper jet dives southeast into the central portions of the US. With the strong jet digging across the Plains, significant troughing is expected to develop over the Midwest early Thursday with an area of surface low pressure developing in Ozarks. This upper trough is expected to deepen and eventually close off over the upper Midwest by Friday morning with an area of low pressure lifting NNE from the Ozarks to near Chicago. A fairly strong surface cold front will advance eastward through the Ohio Valley sometime Thursday night with widespread convection accompanying it.

With regards to the convection for Thursday afternoon/night, themodels generally have the best instability and shear west of the region. This combination of shear and instability will shift
eastward through western/central Kentucky Thursday night. However, the passage of the front during the overnight hours may preclude a larger threat of strong/severe storms. Overall, the shear profiles are not particularly strong, but certainly strong enough to support a wide mode of severe weather. The recent model trends suggests that a better potential for severe weather may develop across our eastern sections during the day on Friday as the cold front slowly progresses eastward through KY as destabilization occurs out ahead of the front. It does appear that instability and shear would be in close proximity to each other which may result in an regional outbreak of severe from the southeast US northeastward along the western spine of the Appalachians.

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
229 PM EDT MON MAY 28 2012

VALID 12Z THU MAY 31 2012 - 12Z MON JUN 04 2012


PRELIMINARY UPDATE...

USED ABOUT TWO-PARTS 00Z/28 ECMWF AND ONE-PART 00Z/28 ECENS MEAN TO UPDATE THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 AND 4...THEN SWITCHED TO AN EVEN BLEND OF THAT GUIDANCE FOR DAYS 5 THROUGH 7 IN AN EFFORT TO MITIGATE THE SYNOPTIC DIFFERENCES BETWEEN THE DETERMINISTIC MODELS VIA A MORE ROBUST INCORPORATION OF THE THE MEAN. THE 00Z/28 GFS AND GEFS MEAN ARE ON THE SLOW SIDE OF THE SPREAD WITH THE BIG WAVE CROSSING THE EASTERN STATES DAYS 4 AND 5. THIS SYSTEM OWES MORE TO THE COLD SEASON THAN NEWLY MINTED METEOROLOGICAL SUMMER...WITH A TRACK ACROSS THE OHIO RIVER...AND CHILLY CANADIAN AIR BEING DRAWN SOUTHWARD INTO THE UPPER MIDWEST ON ITS BACK SIDE. THE CYCLONE...ALSO LIKE WINTER...WILL THEN CRAWL DOWN THE SAINT LAWRENCE VALLEY DURING THE SECOND HALF OF THE FORECAST...KEEPING CONTINENTAL POLAR IN PLACE OVER MUCH OF THE EASTERN UNITED STATES. THE DISPLACED POLAR JET WILL ALSO BRING COOL...UNSETTLED CONDITIONS TO THE FAR WEST...WITH A STRONG TROUGH EDGING INLAND DAYS 6 AND 7.

Toot wrote:

Adam2014 wrote:Also toot, where did you get that weather graphic at I know it is from Noaa but I couldn't find it on the NAM. Who ever is in between the cold front and warm front will have the best chance at seeing tornadoes. That is where the best shear is and the best instability. On the models, it looks like the Tennessee and parts of the Ohio Valley are under the gun. That will change some but right now we could have a severe weather outbreak out our hands.

Its the St Louis WRF
http://www.crh.noaa.gov/lsx/wrf/wrfdisplay.php

BTW...everyone in the state at some point will be in between the warm front and cold front...just saying

Toot wrote:This graphic off of the 12z FIM caught my eye. I was looking at it a few minutes ago. Its been verifying better than the GFS recently

35-40 Kt LLJ streak in Eastern TN/KY

The plateau area is once again one of those areas that COULD have an enhanced risk

Adam2014 wrote:Not neccesairly... The Low pressure system could set up further south and only southern areas could be in between the 2...

Adam2014 wrote:On the NAM, GFS, and SREF I am just not seeing that great upper air strength. I don't know much so correct me if I am wrong but I looked at the 850 MB vort and it is not that impressive. The most impressive wind is around the low pressure system located in Illinois. We have instability and moisture we are lacking upper air strenghth though... I am just going by what I saw on the Vort maps which I have no idea if they help or not....

Adam2014 wrote:On the NAM, GFS, and SREF I am just not seeing that great upper air strength. I don't know much so correct me if I am wrong but I looked at the 850 MB vort and it is not that impressive. The most impressive wind is around the low pressure system located in Illinois. We have instability and moisture we are lacking upper air strenghth though... I am just going by what I saw on the Vort maps which I have no idea if they help or not....

Eric wrote:I'm going to be honest...I've looked over the 18z data, and for the life of me, I just cannot find anything that screams "severe event"

Eric wrote:

Adam2014 wrote:On the NAM, GFS, and SREF I am just not seeing that great upper air strength. I don't know much so correct me if I am wrong but I looked at the 850 MB vort and it is not that impressive. The most impressive wind is around the low pressure system located in Illinois. We have instability and moisture we are lacking upper air strenghth though... I am just going by what I saw on the Vort maps which I have no idea if they help or not....

While not always "required" for severe wx, it's always nice to have that upper-level jet rounding the base of the trough. As it exits to the SE of the trough axis - or exit region - it provides upper-level divergence, which in turn, allows for storm development. Given this case, and the caveat that things COULD change, the proximity of the closed cyclonic system could provide enough upper-level divergence that the ULJ isn't needed.

Talking about vorticity maps, I wouldn't worry too much with the 850mb map. Generally speaking, whatever happens at 500mb will dictate how the system behaves. You can look at the 850mb wind directions to gain an idea of the strength and location of the LLJ, but other than that, I find the 850mb maps rather useless during severe weather season. If you wanted to see how much "shear" is available, look at the 0-1km, 0-3km, and 0-6km bulk shear products. They can provide a decent cross-section of the atmosphere so one can actually see which atmospheric layer is turning more rapidly.