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April 2nd - April 5th Severe Weather


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Just crossed into Iowa at Burlington. Gonna head west towards Mt. Pleasant or Fairfield. My home computer took a crap on me this morning, so I don't know if I'll be able to get on later tonight when I get back. Looks like I'll be buying a new one tomorrow.

Anyway, a little worried about the cap holding. Some of the RUC runs keep it just strong enough to hold off initiation until after sunset. The other parameters are so good we couldn't pass this up though.

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Were at Wendys in Muscatine, IA (same thing as June 5th) you know my superstitious problem lol but going to be heading north and east from here closer to the warm front/triple point where the more favorable low-level flow will be.

Dont like down near BRL and into MO due to the veered sfc winds and think things will go linear quickly. Any shot at a tornadic supercell I think is going to be northeast IA into northwest IL *if* the moisture can get there.

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I think N Il is the area to watch for tornadoes 7-11pm..S IA may bust CAP..time will tell

It just looks "cappy" on Sat. now over MO into s IA

but some CU may be going up over eastern IA now under the cirrus

We agree. Some serious low-level shear juxtaposed with more than decent instability in extreme eastern IA north of I-80 into northwest IL at 0z. If a discrete supercell goes up before dark its going to have to produce, will have southerly to even slightly backed sfc winds in that area.

The latest RUC has the sfc low pretty far south at 0z in eastern IA, centered close to IOW.

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sveral 90 degree readings in eastern kanas..wow 90/58 LAWRENCE

Can you say "well-mixed boundary layer?" Dew points look to be running 3-5 F below model consensus throughout most of the warm sector.

Lots of mid-upper 90s behind the dryline. DDC has already smashed their record by several degrees. CDS sitting at a cool 100 F.

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19Z update, my model starting to now catch up to the changes, with more surface data history now available. Highest threat spreading in a line from Kansas City to Quincy, IL to Decatur, IL to just north of St. Louis. Quincy, IL area has the greatest threat of Tornadoes, as of 19Z,seeing 0-3Km Shear around 61kts, 0-1KM EHI are 3.4, and 0-3KM SRH around 353 with overall CAPE's around 2000 (J/kg). I think area from Decatur to Quincy will be the most action. As for further south into E. KS and OK into N. TX, again capping is the main issue, but trying to show hints of possible Isolated convection in that area. 19Z City Specific Severe analysis is uploaded http://smartwxmodel.net/severe.pdf

03APR1.jpg

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO

107 PM CDT SUN APR 3 2011

..UPDATED PUBLIC/CLIMATE/AVIATION DISCUSSIONS

DISCUSSION

..MESOSCALE DISCUSSION

12Z KTOP SOUNDING NOT SURPRISING IN THE LEAST WITH AN UNSEASONABLY

STRONG ELEVATED MIXED LAYER/CAP NOW PRESENT ACROSS THE REGION. 60-70

KNOT LLJ OVERNIGHT DELIVERED AS EXPECTED...WITH SURFACE DEWPOINTS

NOW RUNNING IN THE LOWER 60S WITH NOONTIME TEMPERATURES ALREADY AT

OR ABOVE 80 DEGREES. RECORD HIGHS WILL SURELY BE BROKEN WITH AMPLE

SUNSHINE EXPECTED THIS AFTERNOON.

SHIFTING FOCUS FOR THE SEVERE THREAT LATE THIS AFTERNOON...

TEMPERATURES IN THE MID 80S AND LOW 60F DEWPOINTS WILL ALONE BE

INSUFFICIENT TO BREAK THE INCREDIBLE 22C 850MB TEMPERATURE PRESENT

ON THE KTOP 12Z SOUNDING. IN FACT CANT EVER RECALL SEEING A CAP THIS

STRONG THIS EARLY IN THE SEASON. HOWEVER...THE ELEVATED MIXED LAYER

IS ALSO EXTREMELY DRY AND THUS HAS AMPLE ROOM TO COOL IF LIFT IS

APPLIED. BOTTOM LINE...WHEN MODIFIED FOR AFTERNOON CONDITIONS THE

CAP IS BREAKABLE WITH CONVECTIVE ALLOWING MODELS SHOWING THIS

OCCURRING ALONG A ST. JOSEPH TO LAMONI IOWA LINE SOMEWHERE IN THE 23

TO 00Z WINDOW. VERY STEEP /NEAR DRY ADIABATIC/ MID-LEVEL LAPSE RATES

WILL YIELD STRONG INSTABILITY APPROACHING 2500 J/KG...MOST OF WHICH

IS LOADED IN THE PREFERRED HAIL GROWTH REGION.

DO HAVE SOME CONCERNS REGARDING CONVECTIVE MODE. THE CLOUD BEARING

SHEAR REMAINS AN ISSUE...AS THE HODOGRAPH REMAINS LARGELY BUNCHED

ABOVE 2KM WITH WINDS UNIFORMLY OUT OF THE WSW AT 40-45 KNOTS. WHILE

A FEW THUNDERSTORMS CAPABLE OF VERY LARGE HAIL ARE POSSIBLE AT

INITIATION...STRONG FLOW PARALLEL TO THE SURFACE BOUNDARY SUGGESTS

THAT A LINEAR MODE MAY BE QUICKLY ATTAINED. IN ADDITION...INDIVIDUAL

UPDRAFTS MAY HAVE SHORT LIFE SPANS AS STORM MOTION TOWARD THE

NORTHEAST SUGGESTS STORMS WILL BE QUICKLY UNDERCUT BY THE SOUTHEAST

SURGING COLD FRONT. THE LAST NEGATIVE FACTOR WILL BE WITH THE STRONG

VEERED SURFACE FLOW THAT WILL RESULT FROM THE LACK OF PRESSURE FALLS

AHEAD OF TWO FAIRLY WEAK SURFACE CYCLONES ACROSS IOWA AND SW KS.

ALL IN ALL...LARGE HAIL APPEARS TO BE THE PRIMARY THREAT THROUGH THE

EARLY EVENING AND COULD BECOME THE ONLY THREAT DEPENDING ON HOW FAST

STORMS ARE UNDERCUT AT THE SURFACE. A LOCALIZED DAMAGING WIND THREAT

MAY ALSO EXIST WITH EMBEDDED BOWING STRUCTURES OR AS THE STORMS GROW

UPSCALE...BUT AGAIN THIS MAY BE MITIGATED BY STORMS QUICKLY BECOMING

ELEVATED AS WELL.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0300 PM CDT SUN APR 03 2011

VALID 032000Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS EASTERN KS AND NORTHERN

MO...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS/LOWER

MO VALLEY TO LAKE MI VICINITY...

..SE IA/N IL AND MO/E KS THIS EVENING INTO TONIGHT

FEW CHANGES TO PREVIOUS OUTLOOK. INITIAL DEEP CONVECTIVE DEVELOPMENT

IS ANTICIPATED TO OCCUR LATE THIS AFTERNOON OR MORE LIKELY EARLY

THIS EVENING WITHIN A GENERAL SW-NE NEAR-FRONTAL CORRIDOR FROM

AROUND THE KC METRO TO NEAR KIRKSVILLE MO/QUINCY IL...TO EXTREME

SOUTHEAST IA/NORTHWEST IL INCLUDING NEAR/EAST OF THE QUAD CITIES.

LATEST EXPERIMENTAL HRRR GUIDANCE...ALONG WITH AN ASSORTMENT OF 15Z

SREF MEMBERSHIP SUGGESTS THIS COULD OCCUR BY AROUND 23Z-00Z...WITH A

SIMILAR/BUT A FEW HOUR DELAYED SOLUTION AS INDICATED BY THE 12Z

WRF-NMM. INITIALLY...FAST EASTWARD-MOVING SUPERCELLS /40-45 KT/ ARE

PROBABLE...INCLUDING ASSOCIATED POTENTIAL FOR LARGE HAIL AND

ISOLATED TORNADOES...BEFORE A QUASI-LINEAR MODE /INCLUDING BOWS WITH

DAMAGING WINDS/ BECOMES DOMINANT BY LATE EVENING/OVERNIGHT.

OTHERWISE...SEE PRIOR OUTLOOK DISCUSSION BELOW AND ANY SUBSEQUENT

MESOSCALE DISCUSSIONS/WATCHES LATER TODAY.

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DVN downplaying tornadoes

TONIGHT...LOCAL CALCULATIONS COMBINED WITH MET-WATCH TOOLS SUGGEST

ISOLATED TO SCATTERED STORMS TO DEVELOP BETWEEN 5 AND 7 PM THIS

EVENING ALONG THE STRONG COLD FRONT NOW IN CENTRAL IOWA. CHALLENGE

IS LIMITED FORCING ALOFT WITH BEST CONVECTION SUGGESTED TO OCCUR IN

NORTH TO NORTHWESTERN MISSOURI. COOL DRY AIR ALOFT TO ALLOW FOR

FAVORABLE LARGE HAIL PRODUCTION AND GUSTY STRAIGHT LINE WINDS. LOCAL

SUB-CLOUD SHEAR IS MARGINAL FOR TORNADOES ATTM UNLESS WINDS BACK

AHEAD OF THE COOL FRONT WHICH APPEARS UNLIKELY. SOME LOCATIONS MAY

SEE HAIL COVERING THE GROUND WITH POTENTIAL FOR GOLF BALL TO POSSIBLY

EVEN NEAR BASEBALL SIZED HAIL IN THE VERY STRONGEST STORM UPDRAFTS...

ALONG WITH 60 TO 70+ MPH WINDS DUE TO STRONG EVAPORATIVE COOLING AND

LOTS OF MOMENTUM TRANSFER OF LOW LEVEL JET. THESE ARE BASED ON SBCAPE

OF 1200-1600 J/KG DERIVED FROM T/TD VALUES OF ~77/60 DEGREES.

CONCEPTUAL TRENDS AND FORCING SUGGEST THE SOUTH 1/3 SECTIONS ARE MOST

AT RISK AS THESE STORMS TO COALESCE INTO A LINE BY MID EVENING. BEST

TOOLS AT 2 PM...SUGGEST NORTH MISSOURI MAY BE AT RISK FOR THE LARGEST

HAIL AND STRONGEST WINDS.

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