B-Rent Posted February 24, 2011 Share Posted February 24, 2011 the storm B4 on wunderground was a purple triangle,now its back to just the yellow meso marker. anyoone know how sound the logic is behind the purple TVS that can sometimes show up on wundergound? http://en.wikipedia....ortex_signature http://www.wrh.noaa.gov/wrh/LITETAs/TALITE9611/talite9611.html Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 24, 2011 Share Posted February 24, 2011 The convection east of Lubbock fired on a boundary (Its too early for me to even go look what that might be, I'd guess the dryline) with dewpoints in the 20's to the west and 40's to the east. No lighting is being produced, but I think this shows pretty well how much shear is in place. There is a dryline in place--but the storms are developing along an elevated dynamically induced low level jet in response to increasing DPVA ahead of the ejecting wave. Based on soundings they must be at least above 850. Some pretty insane lapse rates in place associated with the eastward progressing EML. Link to comment Share on other sites More sharing options...
thewxmann Posted February 24, 2011 Share Posted February 24, 2011 Kinda interesting, but the 0Z 4km WRF showed cells erupting in wrn TN right where yesterday's 12Z 4km WRF showed it, at the same time too (around 23-0Z). I'm not sure if that will go down, but interesting to see nonetheless. I am more focused on the activity that will fire up along the pre-frontal trough later today, and whether that will be linear or discrete. This is in light of the trend of keeping the quality airmass suppressed and south, so I am slightly less confident of tornadic action in advance of the surface low. Also watch moisture quality today; an increase of dewpoint by a few degrees will make a huge difference WRT instability. Another possible fly in the ointment is a 700mb thermal ridge that is hinted at in some of the models, which would drastically reduce instability. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 24, 2011 Share Posted February 24, 2011 Not much change. snip of discussion... ADDITIONAL TSTMS EXPECTED TO FORM TOWARD MIDDAY OR BY EARLY AFTN ALONG CONFLUENCE AXIS FROM ERN OK/WRN AR SSW THROUGH THE ARKLATEX INTO E TX. A FEW STORMS ALSO MAY FORM NEAR INTENSIFYING WARM FRONT EXTENDING ENE FROM THE AR SFC LOW INTO WRN/MIDDLE TN. BOTH THE CONFLUENCE AXIS STORMS AND THOSE ALONG THE WARM FRONT WILL HAVE ACCESS TO THE RICHEST MOISTURE INFLOW AND MAXIMUM SFC HEATING OF THE PERIOD...WITH POCKETS OF SBCAPE EXPECTED TO BE AOA 1250 J PER KG. IN ADDITION...LOW- TO MID-LVL SHEAR WILL INCREASE SUBSTANTIALLY BY LATE IN THE DAY AS CORE OF 50+ KT 700 MB SW FLOW ASSOCIATED WITH NM UPR IMPULSE OVERSPREADS REGION. THUS...THE AR AREA STORMS WILL POSE A THREAT FOR HIGH-IMPACT SVR WEATHER INCLUDING SUPERCELLS WITH BOWING SEGMENTS/HIGH WINDS...LARGE HAIL...AND POSSIBLY STRONG TORNADOES. THE TORNADO THREAT WOULD APPEAR TO BE GREATEST FROM LATE THIS AFTN THROUGH EARLY TONIGHT NEAR WARM FRONT OVER CNTRL/NERN AR AND WRN/MIDDLE TN...WHERE 200-300 M2/S2 0-1KM SRH WILL EXIST INVOF DEEPENING SFC LOW. Link to comment Share on other sites More sharing options...
David Reimer Posted February 24, 2011 Share Posted February 24, 2011 12Z RUC has convection developing in SW/S AR by 19Z with parameters favoring significant severe weather. By sunset, Little Rock is in some deep sh-t. I'm about to leave the comfort of my warm bed in Dallas to go chase fast-moving supercells in the jungle. Link to comment Share on other sites More sharing options...
Srain Posted February 24, 2011 Share Posted February 24, 2011 Early in the the day, but it's a start... MESOSCALE DISCUSSION 0123 NWS STORM PREDICTION CENTER NORMAN OK 0747 AM CST THU FEB 24 2011 AREAS AFFECTED...NWRN TX THROUGH SW AND CNTRL OK CONCERNING...SEVERE THUNDERSTORM WATCH 12... VALID 241347Z - 241545Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 12 CONTINUES. SOME THREAT FOR HAIL AND ISOLATED STRONG WIND GUSTS WILL CONTINUE FOR THE NEXT COUPLE HOURS FROM NWRN TX INTO CNTRL OK. DEEPER ASCENT ASSOCIATED WITH NEWD EJECTING LEAD SHORTWAVE TROUGH HAS OVERSPREAD NWRN TX THROUGH OK. THIS HAS RESULTED IN A SIGNIFICANT INCREASE IN THUNDERSTORM COVERAGE ALONG AND JUST EAST OF EWD ADVANCING PACIFIC FRONT FROM NWRN TX INTO SWRN OK AS WELL AS ALONG AND NORTH OF SWD ADVANCING POLAR FRONT ACROSS CNTRL THROUGH NERN OK. THE 12Z NORMAN RAOB SHOWS 1500 J/KG MUCAPE AND A LAYER OF 7 C/KM LAPSE RATES BETWEEN 700-500 MB...BUT WITH WEAKER LAPSE RATES ABOVE 500 MB. LATEST OBJECTIVE ANALYSIS INDICATES A NARROW CORRIDOR OF MODERATE INSTABILITY REMAINING FROM NWRN TX INTO CNTRL OK. POTENTIAL STILL EXISTS FOR A FEW CELLS TO PRODUCE HAIL AND ISOLATED STRONG WIND GUSTS...BUT THREAT IS BECOMING INCREASINGLY MARGINAL AS THE MORE UNSTABLE PORTION OF WARM SECTOR IS OVERTURNED. ..DIAL.. 02/24/2011 ATTN...WFO...FWD...OUN...SJT... Link to comment Share on other sites More sharing options...
blackjack123 Posted February 24, 2011 Share Posted February 24, 2011 12Z RUC has convection developing in SW/S AR by 19Z with parameters favoring significant severe weather. By sunset, Little Rock is in some deep sh-t. I'm about to leave the comfort of my warm bed in Dallas to go chase fast-moving supercells in the jungle. Really. Like monster tornadoes. Link to comment Share on other sites More sharing options...
David Reimer Posted February 24, 2011 Share Posted February 24, 2011 Convection beginning to fire here in North Texas. I'm sitting here in Rockwall watching to see how it behaves as I'm in a pretty good intercept point for cells developing down in Ellis County. I'll likely end up in AR later this afternoon. I've got my live stream and GPS up at www.texasstormchasers.com/live for those interested in viewing. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 24, 2011 Share Posted February 24, 2011 NAM has storms around and the NAM forecasting sounding looks like all systems go for various modes of severe. Instability looks meager in the very lowest layers, but I think wind energy and cloud bases below the 900 mb level (~3000 feet) would compensate Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 24, 2011 Author Share Posted February 24, 2011 Visible shows some pockets of clearing in AR/MS yep..those storms along I-35 may be along some sort of prefrontal axis.....winds are backed ahead of them with warming temps and pockets of clearing...memphis is already 68/63 and no model had them over 70(forecast highs upper 60's)....I suspect winds will veer SW behind them in the pocket of clearing bewtween them and the front..if they can become surface based could mean trouble soon Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 24, 2011 Author Share Posted February 24, 2011 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1004 AM CST THU FEB 24 2011 VALID 241630Z - 251200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF THE LWR MS AND LWR TN VLYS... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA...FROM THE SRN PLNS ENE INTO THE LWR OH VLY... ..SYNOPSIS STRONG S/W TROUGH NOW SRN HI PLAINS ON TRACK AND WILL RESULT IN SURFACE CYCLOGENESIS ACROSS ERN OK THIS AFTERNOON. SYSTEM BOTH SURFACE AND ALOFT WILL DEEPEN TONIGHT AS LOW CENTER TRACKS ACROSS NRN AR INTO KY. WARM FRONT NOW ACROSS ERN OK INTO CENTRAL AR AND SRN TN WILL LIFT NWD THIS AFTERNOON ALLOWING A MOIST WARM SECTOR TO SPREAD ACROSS MUCH OF LOWER MS VLY INTO TN VALLEY. COMBINATION OF STRENGTHENING WIND FIELD AND ASCENT WITH PROGRESSIVE TROUGH...CONTINUED MOISTURE INFLOW /WITH PW INCREASING TO AOA 1.50 INCHES/...AND DIURNAL HEATING EXPECTED TO SUPPORT AN OUTBREAK OF SVR TSTMS OVER PARTS OF AR/TN AND ADJACENT STATES LATER THIS AFTERNOON INTO TONIGHT. ..SERN OK/ERN TX ENE INTO THE LWR TN VLY/LWR OH VLYS BY EARLY AFTERNOON MODERATE SFC HEATING WITH TEMPS RISING THRU THE 70S WILL LEAD TO SUFFICIENT INSTABILITY...MLCAPES AOA 1000 J/KG...TO SUPPORT NUMEROUS BANDS/CLUSTERS OF TSTMS ACROSS NERN TX INTO SERN OK/WRN AR AS 90-120 METER MID-LVL HEIGHT FALLS WITH UPR IMPULSE SWEEP ENEWD. RELATIVELY STEEP MID-LVL LAPSE RATES...7C/KM...AND SIZABLE CLOUD-LAYER SHEAR SUGGEST POTENTIAL FOR HAIL AND POSSIBLY SHORT-LIVED BOWING SEGMENTS WITH HIGH WIND AS THE STORMS MOVE/DEVELOP MAINLY ENEWD. A FEW STORMS ALSO MAY FORM NEAR INTENSIFYING WARM FRONT EXTENDING ENE FROM THE DEVELOPING SURFACE LOW ERN OK/WRN AR INTO WRN/MIDDLE TN. WITH LOW TO MID-LVL SHEAR INCREASING SUBSTANTIALLY BY LATER THIS AFTERNOON ASSOCIATED WITH APPROACHING UPR IMPULSE OVERSPREADING THE REGION...ARKANSAS AREA STORMS WILL POSE A THREAT FOR HIGH-IMPACT SVR WEATHER INCLUDING SUPERCELLS WITH BOWING SEGMENTS/HIGH WINDS...LARGE HAIL...AND POSSIBLY STRONG TORNADOES. THE TORNADO THREAT WOULD APPEAR TO BE GREATEST FROM LATE THIS AFTN THROUGH EARLY TONIGHT NEAR WARM FRONT OVER CNTRL/NERN AR AND WRN/MIDDLE TN...WHERE 300-400 M2/S2 0-1KM SRH WILL EXIST INVOF DEEPENING SFC LOW. THERE IS SOME CONCERN THAT THE CURRENT MDT MAY BE A LITTLE FAR N INTO SRN KY GIVEN THE CURRENT VERY COOL BOUNDARY LAYER...HOWEVER WITH THE TRACK OF THE DEEPENING SURFACE LOW ACROSS THIS AREA THERE IS AT LEAST A THREAT OF AN ORGANIZED DAMAGING WIND THREAT AS WELL AS EMBEDDED SUPERCELLS AND TORNADOS. THUS WILL NOT MAKE ANY CHANGES IN THE MDT RISK ATTM. THE STORMS SHOULD EVOLVE INTO AN EXTENSIVE QLCS BY MID-EVE...WITH OVERALL LINE MOVEMENT TO THE ENE ACROSS TN/LWR OH VLYS...AND DEVELOPMENT SWD INTO LA/MS/AL THROUGH THE OVERNIGHT. A CONTINUING THREAT DMGG WIND AND ISOLD TORNADOES LIKELY WILL PERSIST WELL INTO THE NIGHT...ESPECIALLY NEAR TRACK OF SFC LOW ...AND FARTHER S IN AREA OF GREATER SFC-BASED BUOYANCY IN MIDDLE TN...MS...AND NRN/WRN AL. Link to comment Share on other sites More sharing options...
Calderon Posted February 24, 2011 Share Posted February 24, 2011 Pretty drastic temp spread in the Memphis area, not even 25 miles between these two. Memphis Int'l 68/63 West Memphis, AR 59/57 Link to comment Share on other sites More sharing options...
beneficii Posted February 24, 2011 Share Posted February 24, 2011 Pretty drastic temp spread in the Memphis area, not even 25 miles between these two. Memphis Int'l 68/63 West Memphis, AR 59/57 That's strange. Now, the Memphis NWS at the Agricenter in East Memphis has 66/62 as of 9:53 A.M., so I'm wondering what that's saying about which airport is more accurate. I don't see any real reason for there to be such a difference between the two. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 24, 2011 Share Posted February 24, 2011 Link to comment Share on other sites More sharing options...
Calderon Posted February 24, 2011 Share Posted February 24, 2011 That's strange. Now, the Memphis NWS at the Agricenter in East Memphis has 66/62 as of 9:53 A.M., so I'm wondering what that's saying about which airport is more accurate. I don't see any real reason for there to be such a difference between the two. the winds at West Memphis were NW 5 at ob time, while KMEM was SW at 16G23, I'm going with a sharply defined warm front. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 24, 2011 Share Posted February 24, 2011 The latest HRRR is favoring NE. Texas/SW. Arkansas and NW. Louisiana through the end of it's run. Nice area of SB CAPE >1500 up to the Memphis area. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 24, 2011 Share Posted February 24, 2011 That's strange. Now, the Memphis NWS at the Agricenter in East Memphis has 66/62 as of 9:53 A.M., so I'm wondering what that's saying about which airport is more accurate. I don't see any real reason for there to be such a difference between the two. Subtle boundary? Not severe, but well ahead of the big show, after any nocturnal jet has weakened but before much destabilization. Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 24, 2011 Author Share Posted February 24, 2011 Subtle boundary? Not severe, but well ahead of the big show, after any nocturnal jet has weakened but before much destabilization. The LLJ will be getting stornger as the day goes on in this case 50-55kts now forecast to be 65-70 kts by 3pm Link to comment Share on other sites More sharing options...
tornadotony Posted February 24, 2011 Share Posted February 24, 2011 The latest HRRR is favoring NE. Texas/SW. Arkansas and NW. Louisiana through the end of it's run. Nice area of SB CAPE >1500 up to the Memphis area. The HRRR is substantially more unstable than other models. Not sure if it holds a bias, but boy is there going to be trouble if that verifies. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 24, 2011 Share Posted February 24, 2011 12z SPF WRF is out... http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/12/ Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 24, 2011 Author Share Posted February 24, 2011 yep..those storms along I-35 may be along some sort of prefrontal axis.....winds are backed ahead of them with warming temps and pockets of clearing...memphis is already 68/63 and no model had them over 70(forecast highs upper 60's)....I suspect winds will veer SW behind them in the pocket of clearing bewtween them and the front..if they can become surface based could mean trouble soon SPC going with this idea MESOSCALE DISCUSSION 0124 NWS STORM PREDICTION CENTER NORMAN OK 1034 AM CST THU FEB 24 2011 AREAS AFFECTED...PARTS OF ERN OK/TX...WRN AR AND NWRN LA CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 241634Z - 241730Z THUNDERSTORMS ARE GRADUALLY INCREASING IN BOTH AREAL COVERAGE AND INTENSITY WITHIN BROADER WARM CONVEYOR FROM THE I-35 CORRIDOR SOUTH OF THE DFW METROPLEX...NWD INTO OK. THIS ACTIVITY IS EVOLVING WITHIN A VERY STRONGLY SHEARED ENVIRONMENT THAT IS EXPECTED TO ONLY STRENGTHEN INTO THE AFTERNOON HOURS AS LLJ INCREASES IN RESPONSE TO DEEPENING CYCLONE. ALTHOUGH CONSIDERABLE CLOUDINESS IS OBSERVED ACROSS THE WARM SECTOR IT APPEARS LARGE SCALE ASCENT/COOLING WILL GRADUALLY STEEPEN LAPSE RATE ENVIRONMENT ENABLING NEAR-SFC BASED CONVECTION TO ROOT INTO MORE BUOYANT BOUNDARY LAYER PARCELS. SUPERCELLS AND POSSIBLE TORNADOES CAN BE EXPECTED...ESPECIALLY LATER THIS AFTERNOON AS CONVECTION SPREADS INTO THE LOWER MS VALLEY. Link to comment Share on other sites More sharing options...
Reed Stough Posted February 24, 2011 Share Posted February 24, 2011 I am thinking NE TX/SE AK/NW MS. Not sure about central AR as there seems to be a cool pool of air hanging around LIT. It will be interesting to see if things clear out there if they can recover. Radar earlier showed some storms moving towards them - then they quickly died out. Also concerned that places near MEM might see some isolated supercells form along the boundry that is laying over LIT. My other concern is some isolated tornadoes especially along the warm front near PAH and south associated with the backing winds and surface low. Though instability may be limited, but shear will be just fine to over compensate. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 24, 2011 Share Posted February 24, 2011 73 degrees now in southern AR with upper 40's in northeast AR. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 24, 2011 Share Posted February 24, 2011 several runs of the HRRR has been popping discrete cells in eastern AR moving into western TN and northern MS. Link to comment Share on other sites More sharing options...
Reed Stough Posted February 24, 2011 Share Posted February 24, 2011 Springfield MO just did a special update MODERATE RAIN AND THUNDER HAVE PERSISTED THIS MORNING...LIKELY OWNING TO A COMBINATION OF LARGE SCALE MID/UPPER LEVEL LIFT AND BROAD ISENTROPIC ASCENT INTO THE REGION. EXPECTATION FOR THIS AFTERNOON PER SHORT TERM MODEL GUIDANCE IS FOR AFOREMENTIONED SURFACE LOW TO TRACK EAST ACROSS NORTHERN ARKANSAS. BIG QUESTION RIGHT NOW IS EXACT EVOLUTION OF THE WARM FRONT. THUS FAR THIS MORNING...NORTHWARD FRONTAL PROGRESSION APPEARS TO HAVE BEEN HINDERED BY HIGHER TERRAIN/BOSTON MOUNTAINS IN ARKANSAS...AND RUC IS INSISTENT IN CONTINUING THAT TREND THROUGH THE AFTERNOON...BRINGING THE SURFACE FRONT RIGHT UP TO THE ARKANSAS/MISSOURI STATE LINE. REALLY HAVE NO REASON TO DOUBT THIS SOLUTION AT THIS POINT...THOUGH TRENDS WILL BE MONITORED CLOSELY. AREAS JUST ALONG AND SOUTH OF THE WARM FRONT...WHEREVER THAT MAY END UP BEING...WILL HAVE THE POTENTIAL FOR SURFACE BASED CONVECTION AS WE HEAD INTO THE AFTERNOON HOURS...WITH A LEAST A CONDITIONAL TORNADO THREAT IN IMMEDIATE VICINITY OF THE WARM FRONT...OWNING TO ENHANCED HELICITIES AND A MORE MOISTURE-RICH BOUNDARY LAYER. FOR THE SGF CWA...CURRENTLY SUSPECT THAT BEST SEVERE THREAT...ALBEIT NOT A TERRIBLY HIGH ONE...WILL BE ALONG AND SOUTH OF AN ANDERSON TO ROLLA LINE AS A RESULT OF ELEVATED CONVECTION NORTH OF THE WARM FRONT. LOW LEVEL WIND FIELDS ARE EXPECTED TO GET QUITE STRONG THIS AFTERNOON/EARLY EVENING...RESULTING IN STRONG THETA-E ADVECTION NORTH INTO THE CWA...AND THE DEVELOPMENT OF SEVERAL HUNDRED J/K OF MUCAPE. WITH A STABLE BOUNDARY LAYER IN PLACE NORTH OF THE WARM FRONT AND RELATIVELY LOW FREEZING LEVELS BETWEEN 9 AND 10 KFT...HAIL WILL BE THE MAIN SEVERE WEATHER THREAT. I am thinking this will carry east north east into Southern IL/ Southern IN/ and western KY. When you look at radar you see a nice bulge from the LLJ pointing right at SGF. Link to comment Share on other sites More sharing options...
yoda Posted February 24, 2011 Share Posted February 24, 2011 Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 24, 2011 Author Share Posted February 24, 2011 URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 13 NWS STORM PREDICTION CENTER NORMAN OK 1125 AM CST THU FEB 24 2011 THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF A LARGE PART OF ARKANSAS PARTS OF NORTHERN LOUISIANA PASTS OF SOUTHEASTERN OKLAHOMA PARTS OF NORTHEAST TEXAS EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 1125 AM UNTIL 600 PM CST. TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS. DISCUSSION...THUNDERSTORMS ARE INCREASING IN NUMBER ACROSS ERN OK INTO NERN TX AHEAD OF STRONG S/WV TROUGH AND DEVELOPING SURFACE LOW. WITH AIR MASS NOW FAVORABLY UNSTABLE AND NEARLY UNCAPPED...POTENTIAL FOR SEVERE THUNDERSTORMS INCLUDING SUPERCELLS WILL INCREASE EWD ACROSS THE WATCH THRU THE AFTERNOON. E/W WARM FRONT ACROSS CENTRAL AR WILL BE AN AREA FOR ENHANCED LOW LEVEL SHEAR/SUPERCELL DEVELOPMENT. TORNADOS WILL BE POSSIBLE WITH ANY SUPERCELL THAT DEVELOPS. Link to comment Share on other sites More sharing options...
Kevin Askew Posted February 24, 2011 Share Posted February 24, 2011 Myself and Shawn Gossman heading to MEM area very shortly. Link to comment Share on other sites More sharing options...
huronicane Posted February 24, 2011 Share Posted February 24, 2011 12z SPF WRF is out... http://www.emc.ncep....nt4km/conus/12/ SPC WRF keeps showing some storms popping in Central Oklahoma late this afternoon...hmmm... Link to comment Share on other sites More sharing options...
Ellinwood Posted February 24, 2011 Share Posted February 24, 2011 SPC WRF keeps showing some storms popping in Central Oklahoma late this afternoon...hmmm... Upper-level low w/ dry slot FTW Link to comment Share on other sites More sharing options...
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