baroclinic_instability Posted February 2, 2012 Share Posted February 2, 2012 I hate to waffle after my post earlier, but as tantalizing as all these NAM images are, I still have creeping doubts about its moisture advection. I know it nailed November 7, but this time, it really doesn't have much support at all from anything else. The SREF mean dew point plots for tomorrow are laughably different from the operational run, with >55 F confined to areas like San Angelo and Midland by 00z. The SigTor ingredients plot has yet to show a 10% contour on any run thus far. The HRRR and RUC also appear not to be quite as aggressive as the NAM, based on extrapolation. I'm not saying I'll be surprised if the NAM scores a coup, but it's hard to ignore how far out in left field it is in model-land, right now. Yeah good point, however, given the synoptic setup here, I am not so sure SREF will be all that useful since they will mask out the peculiarities of how this synoptic low develops. A pretty classic positive feedback setup here where the timing of rapid deepening being off even 1-2 hrs in a numerical model can fudge things up pretty quickly in the related mass/thermodynamic fields. Non-linear amplification rates can be a pain fin terms of forecasting...more so here since the setup as a whole is dependent upon rapid moisture return, but one would suspect part of the higher dews in the NAM are related to it bombing the synoptic low relatively early in its development cycle. I don't have access to the RGEM data but it probably wouldn't be far behind in moisture return. Link to comment Share on other sites More sharing options...
tornadotony Posted February 2, 2012 Share Posted February 2, 2012 Yeah good point, however, given the synoptic setup here, I am not so sure SREF will be all that useful since they will mask out the peculiarities of how this synoptic low develops. A pretty classic positive feedback setup here where the timing of rapid deepening being off even 1-2 hrs in a numerical model can fudge things up pretty quickly in the related mass/thermodynamic fields. Non-linear amplification rates can be a pain fin terms of forecasting...more so here since the setup as a whole is dependent upon rapid moisture return, but one would suspect part of the higher dews in the NAM are related to it bombing the synoptic low relatively early in its development cycle. I don't have access to the RGEM data but it probably wouldn't be far behind in moisture return. The one good thing is that this event likely won't begin until almost 00z, so there will be plenty of opportunity to watch trends tomorrow and be able to alert people if the NAM/RGEM solution verifies. Link to comment Share on other sites More sharing options...
andyhb Posted February 2, 2012 Author Share Posted February 2, 2012 Day 1: DAY 1 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK 1143 PM CST WED FEB 01 2012 VALID 021200Z - 031200Z ...THERE IS A SLGT RISK OF SVR TSTMS LATE TODAY AND TONIGHT ACROSS PARTS OF THE SOUTHERN HIGH PLAINS INTO THE CENTRAL PLAINS... ...SYNOPSIS... DOWNSTREAM OF A STRONG MID LATITUDE PACIFIC JET...BLOCKING APPEARS LIKELY TO BECOME MORE PROMINENT WITHIN THE LARGE-SCALE UPPER PATTERN ACROSS NORTH AMERICA DURING THIS PERIOD. MODELS INDICATE THAT THIS WILL INCLUDE THE CONTINUED DEVELOPMENT OF AN UPPER HIGH CENTER ACROSS THE PACIFIC NORTHWEST INTO WESTERN CANADA...AND THE COINCIDING EVOLUTION OF A CLOSED LOW OVER THE CENTRAL AND SOUTHERN INTERMOUNTAIN REGION AND ROCKIES. A SERIES OF SHORT WAVE IMPULSES...NOW DIGGING ACROSS THE INTERMOUNTAIN WEST...WILL CONTRIBUTE TO THE FORMATION OF THE LATTER FEATURE...WHILE GRADUALLY PROGRESSING THROUGH THE SOUTHERN PLATEAU AND SOUTHERN ROCKIES...BEFORE LIFTING NORTHEASTWARD ACROSS THE SOUTH CENTRAL HIGH PLAINS. AS THIS OCCURS...LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION...COUPLED WITH NORTHWARD MOISTURE RETURN OFF THE WESTERN GULF OF MEXICO...PROBABLY WILL YIELD SUFFICIENT DESTABILIZATION FOR INCREASING THUNDERSTORM ACTIVITY ACROSS THE SOUTH CENTRAL STATES LATE TODAY INTO EARLY FRIDAY. ONE AREA OF STORMS APPEARS POSSIBLE...PERHAPS AS EARLY AS LATE AFTERNOON...ACROSS SOUTHEAST TEXAS AND CENTRAL GULF COASTAL AREAS. ANOTHER AREA IS EXPECTED IN CLOSER PROXIMITY TO THE LOW...ACROSS PARTS OF THE TEXAS PANHANDLE NORTHEASTWARD INTO THE CENTRAL PLAINS...WHERE STEEPER LAPSE RATES AND STRONGER SHEAR MAY SUPPORT A FEW SEVERE STORMS. ...SOUTHERN HIGH PLAINS INTO CENTRAL PLAINS... AS THE LARGE-SCALE PATTERN TRANSITIONS TO A LESS PROGRESSIVE REGIME...UNCERTAINTY LINGERS CONCERNING THE SMALLER SCALE DEVELOPMENTS...INCLUDING THE TIMING OF SHORT WAVE IMPULSES ACROSS THE SOUTHERN ROCKIES THROUGH THE SOUTH CENTRAL HIGH PLAINS. AND VARIABILITY EXISTS AMONG THE MODELS THAT IMPACTS THE ASSESSMENT OF THE SEVERE WEATHER POTENTIAL. MODELS DO GENERALLY INDICATE THAT DEEP LAYER FLOW FIELDS AND SHEAR WILL STRENGTHEN AS SEASONABLY HIGH MOISTURE CONTENT AIR RETURNS NORTHWARD THROUGH THE PLAINS...BUT LOW-LEVEL CYCLOGENESIS TO THE LEE OF THE SOUTHERN ROCKIES IS PROGGED TO REMAIN RATHER WEAK. FURTHERMORE...STRONGER MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION...TO THE NORTH OF THE CYCLONIC UPPER JET AXIS...MAY REMAIN MOSTLY NORTH OF THE WARM SECTOR. WHILE ISOLATED TO SCATTERED CONVECTIVE DEVELOPMENT DOES NOT APPEAR OUT OF THE QUESTION BY EARLY THIS EVENING ACROSS PARTS OF THE TEXAS PANHANDLE...AND ADJACENT AREAS OF THE SOUTH CENTRAL HIGH PLAINS...THE PRIMARY INCREASE IN CONVECTIVE POTENTIAL MAY NOT OCCUR UNTIL THE 03/03-06Z TIME FRAME. THIS IS WHEN A FOCUSED AREA OF STRENGTHENING LOWER/MID TROPOSPHERIC WARM ADVECTION COULD SUPPORT AN EVOLVING CLUSTER OF STORMS FROM THE EASTERN TEXAS PANHANDLE INTO PARTS OF WESTERN AND CENTRAL OKLAHOMA. SIZABLE CLOCKWISE-CURVED LOW-LEVEL HODOGRAPHS BENEATH 30-50 KT SOUTHERLY 850 MB FLOW MAY CONTRIBUTE TO A RISK FOR POTENTIALLY DAMAGING WIND GUSTS...IN ADDITION TO A RISK FOR LARGE HAIL...IN THE PRESENCE OF MOST UNSTABLE CAPE ON THE ORDER OF 500-1000 J/KG. HOWEVER...THE TENDENCY LIKELY WILL BE FOR ACTIVITY TO BECOME ROOTED ABOVE AT LEAST A SHALLOW NEAR SURFACE STABLE LAYER...PARTICULARLY AS THE NIGHT PROGRESSES...WHICH PROBABLY WILL MINIMIZE THE TORNADIC POTENTIAL. Link to comment Share on other sites More sharing options...
brettjrob Posted February 2, 2012 Share Posted February 2, 2012 Moisture return on the RUC is actually coming into better agreement with the faster NAM idea. Mid 50s dew points should be in place from roughly CDS-LBB by early evening. However, the HRRR and RUC both severely limit surface heating due to clouds along and E of the dryline, so their CAPE values are much lower than the NAM's. Time will tell whether this is realistic. The SWODY1 notes that moisture return is actually overperforming all models in the vicinity of DRT this morning, and bumped up the tornado probs to 5% for after dark in NW TX. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 2, 2012 Share Posted February 2, 2012 Can see the moisture return in earnest now. The leading edge generally marking the upper 40s/lower 50s dewpoints so far, with a second more subtle boundary marking the deeper (60+ dewpoints) moisture. I love these examples of nocturnal moisture return where the temperature difference shows up clearly on the IR. As the sun comes up this will be more clearly marked by visible as the stratus deck. It does feel good to be dusting off the severe weather forecasting skills again. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 2, 2012 Share Posted February 2, 2012 09z SREF trending as well? Link to comment Share on other sites More sharing options...
tornadotony Posted February 2, 2012 Share Posted February 2, 2012 I'm still skeptical about decoupling the boundary layer, given how strong the low-level winds are going to be tonight. I agree with SPC's current forecast but would not be shocked if a tornado threat continued through the night. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 2, 2012 Share Posted February 2, 2012 I'm still skeptical about decoupling the boundary layer, given how strong the low-level winds are going to be tonight. I agree with SPC's current forecast but would not be shocked if a tornado threat continued through the night. I tend to agree regarding the low level winds. Yet the HRRR continues to indicate mainly elevated convection north of the boundary (although the latest run did have a little more vigorous development on the southern end). At the same time it had 1000 J/kg MLCAPE and no CIN plus 500+ m2/s2 0-3km helicity between ABI and CDS. One would think surface development in that area would be a real threat. Link to comment Share on other sites More sharing options...
David Reimer Posted February 2, 2012 Share Posted February 2, 2012 I tend to agree regarding the low level winds. Yet the HRRR continues to indicate mainly elevated convection north of the boundary (although the latest run did have a little more vigorous development on the southern end). At the same time it had 1000 J/kg MLCAPE and no CIN plus 500+ m2/s2 0-3km helicity between ABI and CDS. One would think surface development in that area would be a real threat. The HRRR handled last Wednesday event here in Texas pretty poorly, so I wouldn't put too much faith in its convective output for today. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 2, 2012 Share Posted February 2, 2012 The HRRR handled last Wednesday event here in Texas pretty poorly, so I wouldn't put too much faith in its convective output for today. Well every event is different and guidance can vary along with it. So far this morning the HRRR appears to be doing the best job on dewpoints. At face value, forcing would suggest that meso models should have a decent handle on evolution. Not saying anything will or will not happen, but so far it appears to be doing well. Link to comment Share on other sites More sharing options...
tornadotony Posted February 2, 2012 Share Posted February 2, 2012 http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/12/ Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 2, 2012 Share Posted February 2, 2012 55 dew at SNK and 57 at ABI Link to comment Share on other sites More sharing options...
David Reimer Posted February 2, 2012 Share Posted February 2, 2012 I arrived in Childress about 45 minutes ago and am waiting at a local establishment at Highway 287/ Highway 83. I've got a pretty good road network and besides, if I end up busting I can get back on 287 and head straight home. When I arrived in Childress at 2 PM, the dewpoint was 48 degrees. My vantage vue has a dewpoint of 50°. I noticed the 18/19Z RUC along with the 18Z NAM are saying I'm in a pretty decent location. Time will tell... Link to comment Share on other sites More sharing options...
OceanStWx Posted February 2, 2012 Share Posted February 2, 2012 Just noticed that SPC added a couple new (but similar) overlays to their mesoanalysis. Conditional Probability of a Significant Tornado. Sounds like they use linear regression equations on STP parameters to come up with a probability of a sig. tornado if supercell storms are present. They claim it performs similar to STP, so that would suggest to me that the gradient of this value will be important. Will be interesting to see how this plays out this year. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 3, 2012 Share Posted February 3, 2012 Line of storms along/ahead of the dry line from Boise City down towards Hereford. CU field out ahead of this from around LBB, eastward to CDS and SNK. This setup has yet to impress me, I guess we'll see how it goes though... Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 Dual-pol in action from KAMA. High Z, ZDR near 0 (hail tumbles so Zh - Z v averages out to near 0), CC locally lower but not drastically, and high KDP. This tells me that there is hail in the southern most cell in that line, and it is likely sub-severe and melting/mixing with rain. Link to comment Share on other sites More sharing options...
andyhb Posted February 3, 2012 Author Share Posted February 3, 2012 MESOSCALE DISCUSSION 0093NWS STORM PREDICTION CENTER NORMAN OK 0708 PM CST THU FEB 02 2012 AREAS AFFECTED...PARTS OF THE TX S PLAINS AND PANHANDLE REGION INTO ADJACENT WRN OK CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 030108Z - 030215Z CONVECTION SLOWLY EXPANDING/INTENSIFYING ATTM ACROSS THE TX PANHANDLE REGION CORRESPONDS WITH INCREASING SEVERE RISK. NEW WW WILL LIKELY BE REQUIRED IN THE NEXT HOUR OR SO. LATEST VAD/PROFILER ANALYSIS SHOWS A SLOW INCREASE IN SLY LOW-LEVEL FLOW FIELD ACROSS W TX/WRN OK ATTM...WITH CORRESPONDING INCREASE IN WARM ADVECTION SUPPORTING CONTINUED CONVECTIVE DEVELOPMENT FROM THE TX PANHANDLE EWD/NEWD INTO SWRN OK/SWRN KS. MARGINAL INSTABILITY REMAINS EVIDENT -- PER LATEST OBJECTIVE ANALYSES AND EVENING RAOBS...WHICH HAS ACTED TO LIMIT CONVECTIVE INTENSITY THUS FAR. PARTIALLY OFFSETTING THIS HOWEVER IS AN INCREASINGLY FAVORABLE FLOW FIELD WITH HEIGHT...AS BOUNDARY LAYER SELYS VEER TO SLY AT H85...AND THEN TO SWLY AT 50-70 KT AT H5. OVERALL...EXPECT THREAT TO BE PRIMARILY IN THE FORM OF HAIL -- WITH A FEW STRONGER SUPERCELL STORMS THAT ARE EXPECTED TO EVOLVE LIKELY TO BECOME CAPABLE OF PRODUCING HAIL NEAR 1" IN DIAMETER. THREAT FOR A LOCALLY DAMAGING GUST OR TWO ALSO IS EVIDENT -- PARTICULARLY IF STORMS CAN GROW UPSCALE LINEARLY...AND AN ISOLATED TORNADO OR TWO WILL ALSO BE POSSIBLE GIVEN THE INCREASING LOW-LEVEL SHEAR -- PARTICULARLY ON SERN FRINGES OF THE DISCUSSION AREA WHERE GREATER LOW-LEVEL DEWPOINTS ARE OBSERVED. Link to comment Share on other sites More sharing options...
andyhb Posted February 3, 2012 Author Share Posted February 3, 2012 Looks like a svr tstm watch not a tornado watch. Little early to call it, but I'm leaning towards a bust as far as tornadoes here, unless those cells in the TX Panhandle can get their acts together quick. That said, the watch did have this snippet with it: THE POTENTIAL FOR A TORNADO OR TWO MAY INCREASE LATER TONIGHT ACROSSPARTS OF NWRN TX AND SWRN OK WHERE THE BOUNDARY LAYER MAY MOISTEN SUFFICIENTLY TO SUPPORT STORMS ROOTED IN THE BOUNDARY LAYER. AS SUCH...CONDITIONS WILL CONTINUE TO BE MONITORED FOR A POSSIBLE UPGRADE TO A TORNADO WATCH. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 Better looking cell in Wheeler County, TX. From KAMA there is a decent meso, and CCs are at least dropping below 0.80. That means that at least at 7-8kft there is probably some larger hail (penny to nickel?). Link to comment Share on other sites More sharing options...
on_wx Posted February 3, 2012 Share Posted February 3, 2012 Looks like a svr tstm watch not a tornado watch. Little early to call it, but I'm leaning towards a bust as far as tornadoes here, unless those cells in the TX Panhandle can get their acts together quick. That Wheeler County, TX cell ain't doing too bad. Link to comment Share on other sites More sharing options...
YHM Supercell Posted February 3, 2012 Share Posted February 3, 2012 605 WUUS54 KAMA 030202 SVRAMA TXC211-483-030300- /O.NEW.KAMA.SV.W.0001.120203T0202Z-120203T0300Z/ BULLETIN - EAS ACTIVATION REQUESTED SEVERE THUNDERSTORM WARNING NATIONAL WEATHER SERVICE AMARILLO TX 802 PM CST THU FEB 2 2012 THE NATIONAL WEATHER SERVICE IN AMARILLO HAS ISSUED A * SEVERE THUNDERSTORM WARNING FOR... SOUTHEASTERN HEMPHILL COUNTY IN THE PANHANDLE OF TEXAS WHEELER COUNTY IN THE PANHANDLE OF TEXAS * UNTIL 900 PM CST * AT 800 PM CST...NATIONAL WEATHER SERVICE METEOROLOGISTS HAVE DETECTED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED 7 MILES SOUTHWEST OF WHEELER...OR ABOUT 12 MILES NORTHWEST OF SHAMROCK...MOVING NORTHEAST AT 30 MPH. * LOCATIONS IMPACTED INCLUDE... WHEELER... ALLISON... TWITTY... BRISCOE... KELLERVILLE... PRECAUTIONARY/PREPAREDNESS ACTIONS... TO REPORT SEVERE WEATHER...PLEASE CALL THE NATIONAL WEATHER SERVICE AT 8 0 6 3 3 5 1 1 2 1. && LAT...LON 3521 10031 3536 10052 3579 10019 3569 9999 3546 10000 TIME...MOT...LOC 0202Z 221DEG 28KT 3537 10034 $$ JACKSON/MOULTON Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 Well I was about to say I'm thinking about a warning once the 50 dBZ height reaches 16kft or so in this environment, and AMA just pulled the trigger for Wheeler County. Link to comment Share on other sites More sharing options...
SouthernNJ Posted February 3, 2012 Share Posted February 3, 2012 The storm north of Amarillo may need an SVR as well. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 The storm north of Amarillo may need an SVR as well. Definitely meeting the 50 dBZ criterion, doesn't have as good of a CC signature though. I wonder if that's why AMA is holding off for now. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 Definitely meeting the 50 dBZ criterion, doesn't have as good of a CC signature though. I wonder if that's why AMA is holding off for now. I would probably pull that trigger now. If it's not severe it's awfully close I would think. Link to comment Share on other sites More sharing options...
SluggerWx Posted February 3, 2012 Share Posted February 3, 2012 Definitely meeting the 50 dBZ criterion, doesn't have as good of a CC signature though. I wonder if that's why AMA is holding off for now. Reflectivity north of amarillo looks pretty wicked, like a super tight hook...can anyone post any GR data? Link to comment Share on other sites More sharing options...
OceanStWx Posted February 3, 2012 Share Posted February 3, 2012 Hail signature is a little more pronounced than the first image I posted. Also some evidence of non-uniform beam filling down radial of the supercell. This will happen when the beam has a gradient of ptypes in it. Typically end up seeing low CCs, near zero ZDRs and in extreme cases no KDP (since it's CC is so low). Link to comment Share on other sites More sharing options...
SouthernNJ Posted February 3, 2012 Share Posted February 3, 2012 I would probably pull that trigger now. If it's not severe it's awfully close I would think. They have an SVR now. I was suggesting it a little early because my opinion is that sometimes a warning forecaster should anticipate a storm turning severe in order to give people in towns a heads-up. This storm happened to be heading toward a few towns with a fair amount of people in them. Just my opinion though. Link to comment Share on other sites More sharing options...
SouthernNJ Posted February 3, 2012 Share Posted February 3, 2012 Some rotation showing up to the west of Borger now (832 CST loop). Link to comment Share on other sites More sharing options...
SouthernNJ Posted February 3, 2012 Share Posted February 3, 2012 The former Wheeler county storm is attempting to re-organize as it crosses into Oklahoma. We'll see if it does or not. Link to comment Share on other sites More sharing options...
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