Archive for May, 2011

Strong tornadoes possible from CNTRL NE towards NE SD this afternoon/evening

We were on the move yesterday from OKC to KS and intercepted few LP supercells in N KS along the dryline/warm front. We then headed northwards into eastern NE for the night. Ended up in Norfolk, NE as we wanted to be in a good starting point in case we need to move further north into SE ND. Anyway, looks like we will not need to move far for the chasing today.

Robust setup today across the northern Plains with a trough/cold front crossing in the late afternoon hours. Very narrow windows opportunity exists from CNTRL NE NE-wards into extreme NE SD/extreme SE ND and parts of WSW MN for tornadoes, some of them may be strong if more discrete/isolated storms manage to form especially in NE. It seems there are two area with greatest probability for tornadoes, one close to the CF/WF intersection in SE ND/W MN and the other area in CNTRL NE. We will be likely targeting CNTRL NE as the northern target seem to have a very narrow zone of great potential before it all rapidly goes linear given the almost parallel flow/shear to the SFC frontal boundary there.

SBCAPE AOA 4000 J/kg in CNTRL NE while there is even higher to the NE into E SD/W MN…

Well defined frontal convergence and TP in SE ND/W MN as well as cold front/dryline intersection in CNTRL NE…

Very strong LLJ jet favours strong LL shear for tornadoes, enhanced SREH3 is therefore obviously supporting strong tornadoes if we will see more discrete supercells towards the end of the rapidly forming squall line.

Here is the RUC 12z skewt diagram for Kearney, NE… pretty impressive wind profile/hodograph, supportive of strong tornadoes. Though, it shows quite a CINH/cap, but this area is a bit to the east of the initiation… couldn’t find anything more to the west where UL forcing will be stronger to help eroding the capping inversion. Once it erodes it, it should easily support intense supercells.

We will be on the move from Norfolk to Kearney, NE in early afternoon for the initial target and see how to initiation goes after 20-21z timeframe. Looks like initiation will be close to that timeframe in CNTRL NE.

SPC has issued a MDT risk for the aforementioned areas above… 10% area for tornadoes, 30% hatched for very large hail and 45% hatched for damaging winds given the strong quall line with embedded bowing segments possible…

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1121 AM CDT MON MAY 30 2011

VALID 301630Z – 311200Z

…THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY TONIGHT FROM CENTRAL NEB TO ERN SD…WRN MN…AND EXTREME SE ND…

…THERE IS A SLGT RISK OF SVR TSTMS FROM NORTHWEST OK NORTHWARD ACROSS MUCH OF THE CENTRAL/NORTHERN PLAINS…

A BROAD UPPER TROUGH IS PRESENT TODAY OVER THE WESTERN STATES…WITH A SHORTWAVE TROUGH EVIDENT IN WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH OVER NM. THIS FEATURE WILL LIFT NORTHWARD ACROSS THE HIGH PLAINS THIS AFTERNOON AND EVENING…LEADING TO AN ACTIVE ZONE OF SEVERE THUNDERSTORMS FROM CENTRAL KS INTO THE DAKOTAS AND WESTERN MN.

…NEB/DAKOTAS/MN…
A WEAK SURFACE COLD FRONT CURRENTLY EXTENDS FROM SOUTHEAST ND INTO NORTH CENTRAL NEB. THIS FRONT WILL MOVE ONLY SLOWLY SOUTHEASTWARD TODAY…AND WILL LIKELY RETREAT NORTHWARD LATER TODAY OVER ND/MN AS CYCLOGENESIS OCCURS OVER THE REGION. THE FRONT WILL SERVE AS THE PRIMARY FOCUS FOR THUNDERSTORM INITIATION THIS AFTERNOON AS FULL SUNSHINE OCCURS IN THE WARM SECTOR. AFTERNOON MLCAPE VALUES OF 3000+ J/KG ARE EXPECTED…ALONG WITH A NARROW AXIS OF WEAK CINH ALONG THE FRONT.

PRESENT INDICATIONS ARE THAT STORMS WILL FORM ON THE FRONT AROUND 21Z FROM THE TRIPLE POINT OVER CENTRAL NEB NORTHWARD INTO THE EASTERN DAKOTAS. STRONG WINDS THROUGH THE TROPOSPHERE WILL PROMOTE SUPERCELL STORM STRUCTURES. HOWEVER…ORIENTATION OF FRONT TO UPPER WINDS MAKE STORM-MODE FORECASTS COMPLEX. INITIAL STORMS MAY POSE A RISK OF TORNADOES. BUT A RATHER QUICK EVOLUTION TO A SQUALL LINE APPEARS LIKELY WITH EMBEDDED BOWS POSSIBLE. THROUGH THE EVENING…LARGE HAIL AND DAMAGING WINDS ARE EXPECTED ALONG THE SQUALL LINE AS IT MOVES INTO WESTERN NEB AND NORTHWEST IA.

…KS SOUTHWARD ACROSS THE HIGH PLAINS…
THE DRYLINE WILL EXTEND FROM CENTRAL NEB SOUTHWARD INTO WESTERN OK AND WEST TX. THE POTENTIAL FOR CONVECTIVE INITIATION THIS AFTERNOON AND EVENING IS HIGHEST NEAR THE TRIPLE POINT OVER NEB/NORTHERN KS…AND DECREASES WITH SOUTHWARD EXTENT. STORMS THAT FORM OVER NEB/KS WILL POSE A RISK OF LARGE HAIL…DAMAGING WINDS…AND PERHAPS A TORNADO. HOWEVER…THERE REMAINS CONSIDERABLE UNCERTAINTY REGARDING COVERAGE AND LONGEVITY OF STORMS. FROM WESTERN OK INTO WEST TX…ONLY VERY ISOLATED DRYLINE STORMS ARE EXPECTED.

..HART/GRAMS.. 05/30/2011

Stay tuned!

Rather high based supercells possible from TX Panh into SW KS today

Oh what a waste of juicy conditions yesterday. We intercepted the only storm that initiated in strongly capped environment in CNTRL OK near Dover, OK. Conditions were simply insane… temp 90F, dewp 75F, SBCAPE 6500, EHI3 was the highest I’ve ever seen… 16! But no, when a few towers went up, it all collapsed again. Too strong capping and quite limited mid level relative flow was the issue it seems. Ah what a waste of good conditions.

We ended up in OKC and are now heading towards the SW KS to grab some luck with rather high based storms near the DL/WF intersection. Might be targeting somewhere between Buffalo, OK towards soGreensburg area. Wind profile is very supportive for supercell structures with some hail and wind threat. Would be nice to get some LPs or classic sups.

SPC is out with s SLGT risk there today… with 2% for tornadoes and 15% for large hail and wind…

…TX/OK/KS/NEB…

THE DRYLINE IS EXPECTED TO BECOME ESTABLISHED THIS AFTERNOON FROM THE EASTERN TX PANHANDLE NORTHWARD ACROSS CENTRAL TX INTO SOUTHEAST NEB. STRONG HEATING WEST OF THE DRYLINE COUPLED WITH INCREASING LOW LEVEL CONVERGENCE BY EARLY EVENING ARE EXPECTED TO RESULT IN ISOLATED STORM DEVELOPMENT. CONCENSUS OF MODEL SOLUTIONS INDICATE THE HIGHEST THREAT OF INITIATION WILL BE FROM THE NORTHEAST TX PANHANDLE NORTHWARD INTO CENTRAL KS…AND PERHAPS OVER NORTHEAST KS/SOUTHEAST NEB. THESE STORMS MAY NOT MOVE VERY FAR AWAY FROM THE DRYLINE DUE TO CAPPING OVER THE WARM SECTOR. HOWEVER…THOSE STORMS THAT DO FORM WILL HAVE A THREAT OF LARGE HAIL AND DAMAGING WINDS.

We will be on the move further north into NE/SD for tomorrow’s setup which seems conductive for better storms and tornadoes there. Will post updates tomorrow morning. Stay tuned!

Upslope flow play and supercells possible in Eastern CO

Oh what a frustrating day yesterday! The damned clear sky bust, unreal. Conditions were insane, with 4500 SBCAPE, EHI3 above 10 and eff. shear around 55kt, but no… not a single cloud. The dryline was very sharp and pushing a bulge towards OKC are, but no luck for breaking it. The cap was holding everything, even in the evening there was all capped. Thankfully we made only minor moves and not too expensive bust.

Anyway, we’re now close to Greensburg on route towards E CO for an upslope play this afternoon. We will probably visit my friend Scott who we met back in 2007, a week after the city was hit by an EF-5 tornado and destroyed the city. We will then position ourselves somewhere in ESE CO. There is a nice return moisture into low 50s, marginal CAPE but very good wind profiles for supercells. Its indeed limited probability, but that area is known of CO magic with high based storms and nice structure.

SPC is out with a marginal SLGT risk for E CO and further E into N KS and CNTRL MO…2% for tornadoes and 15% for large hail in E CO…

…E/NE CO THIS AFTERNOON INTO SW NEB/NW KS TONIGHT…

WITH THE DEVELOPMENT OF A NEW LEE CYCLONE IN SE CO…LOW-LEVEL WINDS WILL BECOME SELY THIS AFTERNOON FROM WRN KS INTO ERN CO. THIS WILL DRAW BOUNDARY LAYER DEWPOINTS IN THE 50S OVER SW KS NWWD INTO SE AND E CENTRAL CO. THERE ARE SOME CONCERNS REGARDING THE DEGREE OF WARMING OF THE BOUNDARY LAYER AND ITS POTENTIAL NEGATIVE IMPACT ON INSTABILITY AND STORM COVERAGE. MEANWHILE…THE AREA OF WEAKER CONVECTIVE INHIBITION AND ALSO WEAKER INSTABILITY WILL BE JUST E OF THE FRONT RANGE IN NRN CO. AT THIS TIME…THE SEVERE THREAT APPEARS TO BE MARGINAL ACROSS CO…BUT WILL MAINTAIN THE SLIGHT RISK GIVEN THE POTENTIAL FOR SUPERCELLS IF INSTABILITY TURNS OUT TO BE ON THE HIGH END OF THE EXPECTED RANGE.

We will be targeting somewhere between Lamar and Limon, CO for the initial start and the adjust depends on the activity. Stay tuned!