Ed Lizard Posted November 25, 2011 Share Posted November 25, 2011 I know there are several subforum threads on the potentially unusually deep trough, but I was thinking (dangerous, I know) a thread to discuss where the mode differences are coming from, what teleconnections and indices, current and forecast, might support a particular solution, and a broader look at the implications, on the main forum, where everyone can see the red taggers and more informed hobbyist members post. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 25, 2011 Author Share Posted November 25, 2011 Just an example of the stuff people in only one subforum probably get to see... As some of you probably know, the big problem with these model runs is they really don't have a grasp on what ACTUALLY the northern Pacific jet entails since there is no good data to sample and the STRONG but PROBLEMATIC jet I talked about in my WO. This is the energy that is forecast to dig into the western US this weekend and until it does, models are just guessing where and what she'll do. Next problem is the polar air intrusion early next week (and the other PROBLEM this winter) again no good sample of actual data (see second map on the jets and fourth on tracks I expected this winter based on analogues). The third map shows the tremendous jet channel that's created over the Northern Pacific between the ridge heights and deep polar vortex over the northern Pacific into western Canada in these analogue years. http://weatherhistor...des-in-for.html Link to comment Share on other sites More sharing options...
Srain Posted November 25, 2011 Share Posted November 25, 2011 HPC model diagnostics disco through the UKMET... THE NAM AND GFS HAVE BOTH SHIFTED TOWARD A MORE AMPLIFIED SOLUTION WITH THE UPPER-LEVEL LOW CLOSING OFF FARTHER SOUTH AND REMAINING FARTHER WEST. THE GFS IN PARTICULAR HAS SHIFTED SUBSTANTIALLY TOWARD THE AFOREMENTIONED SOLUTION...ALTHOUGH THE GFS STILL REMAINS FARTHER EAST THAN THE 00Z ECMWF ENSEMBLE MEAN AND 06Z GEFS MEAN. THE TREND IN BOTH THE NAM AND GFS TOWARD THIS SOLUTION LENDS MORE CREDIBILITY TO THE SOLUTION. IN TERMS OF SURFACE FEATURES...A MORE AMPLIFIED UPPER-LEVEL TROUGH WITH A CLOSED LOW FARTHER SOUTH AND WEST WOULD RESULT IN A SLOWER EASTWARD PROGRESSION OF THE SURFACE FRONTAL BOUNDARY AND POTENTIALLY GREATER MOISTURE FLUX NORTHWARD AHEAD OF THE FRONT. THE UKMET HAS BLURRED THE PICTURE SOMEWHAT BY SHIFTING TO AN EVEN SLOWER/MORE AMPLIFIED SOLUTION THAN ITS PREVIOUS RUN. THE UKMET NOW LIES TO THE WEST OF EVEN THE 00Z ECMWF. THE CANADIAN GLBL SOLUTION IS VERY CLOSE TO THE UKMET. WILL BE INTERESTING TO SEE IF THE 12Z ECMWF ALSO SHIFTS FARTHER WEST/SLOWER WITH THE UPPER-LEVEL LOW. IF THE 12Z ECMWF CONTINUES THE WESTWARD SHIFT...THEN EVEN THE PREVIOUS ENSEMBLE MEANS MAY BE TOO QUICK TO PROGRESS THE SYSTEM TO THE EAST. AT THIS POINT...WILL RECOMMEND A COMPROMISE BETWEEN THE 00Z ECMWF AND THE 00Z ECMWF ENSEMBLE MEAN...PENDING THE NEW ECMWF RUN. CONFIDENCE IS BELOW AVERAGE. Link to comment Share on other sites More sharing options...
QVectorman Posted November 25, 2011 Share Posted November 25, 2011 Agreed 120% Ed! Thanks for starting this thread. Hopefully, this thread will catch on!! Link to comment Share on other sites More sharing options...
Srain Posted November 25, 2011 Share Posted November 25, 2011 HPC Final Extended Update: SINCE THEN THE 12 UTC GFS AND RECENT GEFS MEANS HAVE TRENDED SWD/SLOWER...BUT NOT ALL THE WAY BACK TO THE 12Z ECMWF/UKMET AND NOW 12Z CANADIAN. ACCORDINGLY AND CONSIDERING LATEST AMPLIFIED WATER VAPOR LOOP LOOK AND KEEPING AN EYE ON HPC CONTINUITY...ADJUSTED THE FINAL HPC PROGS SLIGHTLY SLOWER THAN OUR PRELIMS...MORE IN LINE WITH THE 00 UTC ECMWF ENSEMBLE MEAN ALOFT. DEPENDING ON ITS UNCERTAIN DEPTH AND TRACK...COMMA HEAD SNOWS COULD STILL SPREAD FROM THE MID-SOUTH NORTHWARD INTO THE UPPER OH VALLEY/ERN GREAT LAKES AND UP THE APPALACHIANS EARLY-MID NEXT WEEK ON THE NORTHWEST PERIPHERY OF WARMER SECTOR ERN SEABOARD HEAVY RAINS. Link to comment Share on other sites More sharing options...
wxmeddler Posted November 25, 2011 Share Posted November 25, 2011 I can't remember such a huge synoptic event (Rockies east) being so poorly modeled 72 hours out with hundreds or a thousand miles of difference between camps with all of the s/w energy onshore! Those looking for a 10 day forecast this weekend are just going to have to wait for an accurate assessment of the situation! Link to comment Share on other sites More sharing options...
Hoosier Posted November 25, 2011 Share Posted November 25, 2011 Difficult setup although we seem to be slowly moving toward some sort of consensus with the large shifts toward the EC/UK/GGEM by the NCEP suite today. Link to comment Share on other sites More sharing options...
Amped Posted November 25, 2011 Share Posted November 25, 2011 UKMET GGEM EURO and Nogaps handeld this okay 72 hrs out. GFS and NAM were in their own crazytown. A splitting shortwave is the hardest thing for models to handel IMO. They need to divide up the energy just right. Models can have big disagreements on these until the back end of the shortwave gets onshore in the PACNW. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 26, 2011 Author Share Posted November 26, 2011 HPC early model disco SOUTHERN STREAM DEEP CYCLONE FORMING/DRIFTING ACROSS THE DEEPSOUTH... PREFERENCE: 18Z GFS/12Z ECMWF COMPROMISE WITH AVERAGE CONFIDENCE THE 00Z GFS DOES NOT LOOK WELL INITIALIZED WITH A SHORTWAVE IN WYOMING. ITS HEIGHTS IN THE SHORTWAVES VICINITY AT 500 HPA ARE IN ERROR ABOUT 20 METERS...BUT THIS COULD BE WHY ITS DEEP CYCLONE ENDS UP NORTH OF THE OTHER DETERMINISTIC GUIDANCE. THE 00Z NAM LOOKS BETTER INITIALIZED HERE. Link to comment Share on other sites More sharing options...
Srain Posted November 26, 2011 Share Posted November 26, 2011 This storm complex looks to offer many different facets. What an interesting setup for this time of year and in a La Nina pattern. DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1125 PM CST FRI NOV 25 2011 VALID 261200Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER MS VALLEY... ...LOWER MS VALLEY... LATEST SHORT RANGE MODEL GUIDANCE IS A BIT MORE AGGRESSIVE IN THE PROGRESSION OF PLAINS UPPER TROUGH AS IT DIGS TOWARD THE ARKLATEX AND FORMS A CLOSED CIRCULATION BY THE END OF THE PERIOD. THIS EVOLUTION IS SUPPORTED BY STRENGTHENING MID LEVEL FLOW ON THE BACK SIDE OF TROUGH OVER THE CNTRL ROCKIES WHICH SHOULD DRIVE SEWD INTO TX LATE IN THE PERIOD. NET RESULT WILL BE FOR A SHARPENING FRONTAL ZONE ACROSS WRN AR/ERN TX BY 18Z BEFORE SURGING ACROSS THE LOWER MS VALLEY DURING THE OVERNIGHT HOURS. EARLIER THOUGHTS WERE MOISTURE/INSTABILITY WOULD BE A BIT MEAGER TO SUPPORT ORGANIZED SEVERE THUNDERSTORMS. HOWEVER 00Z GUIDANCE SUGGESTS SUFFICIENT BOUNDARY LAYER MOISTENING WILL OCCUR AHEAD OF THE COLD FRONT SUCH THAT SFC-BASED INSTABILITY WILL EASILY BE ATTAINED ALONG/AHEAD OF COLD FRONT...POSSIBLY AS EARLY AS 17-18Z. GIVEN THAT DEEP LAYER SHEAR WILL EASILY SUPPORT ORGANIZED ROTATING UPDRAFTS...IT APPEARS THE THREAT FOR EMBEDDED SUPERCELLS ALONG A FORCED FRONTAL SQUALL LINE WILL BE POSSIBLE. LATEST THINKING IS DAMAGING WINDS WILL BE THE PRIMARY SEVERE THREAT DUE TO THE EXPECTED LINEAR STRUCTURE. EVEN SO STRONG LOW LEVEL SHEAR AND LOW LCL HEIGHTS FAVOR AT LEAST A THREAT FOR ISOLATED TORNADOES. PROGRESSION OF ORGANIZED SEVERE SHOULD BE LIMITED BY WEAKER BUOYANCY OVER ERN MS/SWRN AL. ..DARROW/SMITH.. 11/26/2011 Link to comment Share on other sites More sharing options...
kab2791 Posted November 26, 2011 Share Posted November 26, 2011 MODEL DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 130 AM EST SAT NOV 26 2011 VALID NOV 26/0000 UTC THRU NOV 29/1200 UTC SOUTHERN STREAM DEEP CYCLONE FORMING/DRIFTING ACROSS THE DEEP SOUTH... PREFERENCE: 00Z UKMET/00Z ECMWF COMPROMISE WITH AVERAGE CONFIDENCE THE 00Z GFS DOES NOT LOOK WELL INITIALIZED WITH A SHORTWAVE IN WYOMING. ITS HEIGHTS IN THE SHORTWAVES VICINITY AT 500 HPA ARE IN ERROR ABOUT 20 METERS...BUT THIS COULD BE WHY ITS DEEP CYCLONE ENDS UP NORTH OF THE OTHER DETERMINISTIC GUIDANCE. THE 00Z NAM LOOKS BETTER INITIALIZED HERE. MERCIFULLY...THE DETERMINISTIC/ENSEMBLE MEAN GUIDANCE IS IN MUCH BETTER AGREEMENT WITH THIS SYSTEM THAN SEEN 24 HOURS AGO. HOWEVER...THE GFS/UKMET/ECMWF SOLUTIONS HAVE CHANGED SOMEWHAT SINCE THEIR PRIOR RUNS /TRENDING NORTHEAST TO VARYING DEGREES/...IMPLYING THAT THE GUIDANCE MAY NOT HAVE COMPLETELY SETTLED ITS ISSUES IN REGARDS TO THIS SYSTEM. INTERACTIONS BETWEEN THE NORTHERN AND SOUTHERN STREAM REMAIN TRICKY/MORE CHANGEABLE THAN MOST OTHER TYPES OF FLOW PATTERNS WITHIN NUMERICAL WEATHER PREDICTION OUTPUT. THE OVERALL THE 12Z GLOBAL ENSEMBLE GUIDANCE STILL SHOWS A BIT OF SPREAD WITH PROGRESSION /CENTRAL TEXAS TO OFFSHORE NORTH CAROLINA/...THOUGH MOST OF THE MEMBERS NOW LIE AT LOW LATITUDE...CLOSE TO THE 33RD PARALLEL. THE 12Z GEFS MEMBERS/18Z GEFS MEAN SHOW A SLOWER PROGRESSION THAN THE 12Z ECMWF ENSEMBLE MEMBERS AND MEAN...WHICH IS IN CONTRAST TO THE 00Z GEFS MEAN WHICH IS QUICKER/NORTHEAST. IT DOES NOT APPEAR THAT THE RUN-TO-RUN AND DAY-TO-DAY CHANGES IN THE GEFS MEAN ARE DONE...LOWERING CONFIDENCE IN ITS USE. HOWEVER...AT LEAST ONE PIECE OF DETERMINISTIC GUIDANCE IS SHOWING ITS NORMAL BIAS WITH CLOSED CYCLONES...TOO SLOW IN THE CASE OF THE CANADIAN SOLUTION. THE 00Z GFS IS THE DEEPEST ALOFT. WITHIN MOST OF THE GUIDANCE...COMMA HEAD SNOWS FOR THE DEEP AND MID SOUTH ARE POSSIBLE WHICH WOULD BE QUITE EARLY IN THE SEASON FOR SUCH AN EVENT. THE 00Z GFS IS A COMPLETE OUTLIER WITHIN THE DETERMINISTIC GUIDANCE WITH THIS SYSTEMS PLACEMENT AND DEPTH...LYING ON THE NORTHERN FRINGE OF THE 12Z GLOBAL ENSEMBLE GUIDANCE LIKELY DUE TO ITS IMPROPER INITIALIZATION...SO WILL CONSIDER ITS SOLUTION TOO FAR NORTH. HOWEVER...THE 00Z UKMET/00Z ECMWF SHIFTED NORTHEAST FROM ITS PREVIOUS RUN...MATCHING THE 12Z ECMWF ENSEMBLE MEAN. THE GUIDANCE HAS DEFINITELY TRENDED DEEPER WITH THIS SYSTEM SINCE THIS TIME YESTERDAY...CONVERGING UPON THE DEPTH SEEN ON CANADIAN RUNS 24-36 HOURS AGO...WHICH MEANS THEIR STANDARDIZED ANOMALIES AT 500 HPA ACROSS LOUISIANA ARE QUITE SIGNIFICANT...OVER FIVE STANDARD DEVIATIONS BELOW CLIMATOLOGY BY TUESDAY MORNING...IMPLYING A RECORD/VERY UNUSUAL EVENT FOR LATE NOVEMBER IS IN THE CARDS. TO ACCOUNT FOR RECENT NORTHEAST TRENDS ALOFT...WILL PREFER A COMPROMISE BETWEEN THE 00Z UKMET/00Z ECMWF. CONFIDENCE IS AVERAGE BECAUSE OF THE LARGE SPREAD STILL SEEN AMONGST THE GLOBAL ENSEMBLE GUIDANCE IN A FEW DAYS...CONTINUING RUN-TO-RUN AND DAY-TO-DAY INSTABILITY IN THE DETERMINISTIC GUIDANCE...AND THE UNCLIMATOLOGICAL DEPTH SHOWN BY THE DETERMINISTIC GUIDANCE. THE 21Z SREF MEAN/00Z NAM NOW APPEAR TO BE TOO FAR TO THE SOUTH WITH THIS SYSTEM AND LESS USEFUL. FOR WINTER WEATHER IMPACTS OF THIS SYSTEM...CONSULT HPC WINTER WEATHER PRODUCTS AND OUR HEAVY SNOW/ICING DISCUSSION...WHICH ARE DUE AT 0930Z/0430 AM EST. Link to comment Share on other sites More sharing options...
Ed Lizard Posted November 26, 2011 Author Share Posted November 26, 2011 FoothillsNC has a thread started, with frequent interesting updates and analysis of the situation in the SE subforum. I know snow in the Mid-South is the most 'sexy' aspect, but flooding in the upslope regions of the Apps might be the bigger story in the end. Link to comment Share on other sites More sharing options...
Srain Posted November 27, 2011 Share Posted November 27, 2011 Looks like a flood potential for many along the Eastern track of the Upper Low... Link to comment Share on other sites More sharing options...
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