HPC has some confidence with this one
Posted by
JAC on 1/20/2011, 3:13 pm
EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 202 PM EST THU JAN 20 2011 VALID 12Z SUN JAN 23 2011 - 12Z THU JAN 27 2011 MEDIUM RANGE GUIDANCE CONTINUES TO DISPLAY MEANINGFUL SPREAD WITH IMPORTANT SHRTWV DETAILS WITHIN AN AMPLIFIED ERN PAC/WEST COAST MEAN RIDGE AND ERN NOAM MEAN TROF CONFIGURATION. ONE OF THE MOST SIGNIFICANT UNCERTAINTIES YET TO BE RESOLVED INVOLVES THE EXACT SHAPE OF THE RIDGE AS OF DAY 4 MON... AND IMPACT ON DOWNSTREAM FLOW. OPERATIONAL ECMWF RUNS AND ECMWF ENSEMBLE MEANS ALONG WITH THE UKMET HAVE BEEN SHOWING A LESS AMPLIFIED RIDGE THAN MOST RECENT GFS/GEFS MEAN SOLNS. THE FLATTER RIDGE OF THE ECMWF CLUSTER LEADS TO LESS SWWD ELONGATION OF DOWNSTREAM FLOW THAN INDICATED BY THE GFS CLUSTER. HOWEVER SOME GFS RUNS SUCH AS THE 12Z/19 AND 00Z/20 RUNS HAVE BEEN FAIRLY STRONG WITH THE WRN RIDGE BUT STILL SHOWED MORE CONSOLIDATION OF ENERGY OVER THE PLAINS LIKE THE ECMWF SCENARIO. THE CANADIAN HAD BEEN IN THE ECMWF CLUSTER 24 HRS AGO BUT LATELY HAS TRENDED TOWARD THE GFS SCENARIO TO SOME EXTENT. EITHER SCENARIO STILL APPEARS PLAUSIBLE BUT PERSISTENCE WITH SYSTEMS FLOWING ACROSS THE NRN PAC MAY FAVOR LEANING A LITTLE MORE TOWARD THE ECMWF IDEA.
THESE DIFFS THAT DEVELOP BY EARLY NEXT WEEK PROPAGATE DOWNSTREAM TO AFFECT SFC EVOLUTION ALONG THE GULF COAST AND THEN OVER THE EAST COAST/WRN ATLC. THE 06Z GFS IS THE MOST EXTREME SOLN WITH SWWD ELONGATION ALOFT OVER THE WRN HALF OF THE CONUS AND FAST EJECTION OF PLAINS ENERGY... SO IT IS FARTHEST OFFSHORE AT THE SFC BY DAY 6 WED. THE SEPARATION OF SWRN ENERGY IN THE 06Z GFS ALSO LEADS TO ANOTHER GULF WAVE BY DAY 7 AS THAT ENERGY EJECTS EWD. THE 00Z GFS COMPARES MUCH BETTER TO WHAT CONSENSUS EXISTS ALOFT BUT ITS SFC SOLN OFF THE EAST COAST IS SIMILAR TO THE 06Z RUN. EVEN WITH SOME MID LVL DIFFS THE 00Z ECMWF/CANADIAN END UP WITH A SFC LOW OFF SRN NEW ENGLAND... ALBEIT WITH DIFFERENT STRENGTHS... BY DAY 6 WED. THIS SOLN IS CONSISTENT WITH YDAYS FCST. AT THIS TIME ENSEMBLE MEANS SHOW LOW PRESSURE JUST OFF THE EAST COAST BUT THE SPREAD AMONG INDIVIDUAL MEMBERS IS SUFFICIENTLY GREAT TO KEEP THE MEAN FCSTS FAIRLY WEAK.
BEHIND THIS SYSTEM THERE IS DECENT AGREEMENT ON ANOTHER SURGE OF NRN STREAM ENERGY WHICH BY DAY 7 THU SHOULD BRING AN AREA OF WEAK LOW PRESSURE AND TRAILING FRONT INTO THE E-CNTRL CONUS. THE GFS/ECMWF AND THEIR RESPECTIVE ENSEMBLE MEANS ALL SHOW BETTER THAN AVERAGE CLUSTERING WITH THIS FEATURE AND SURROUNDING FLOW.
ABOVE CONSIDERATIONS GENERALLY FAVOR A CONSENSUS/BLEND APPROACH TO ACCOUNT FOR LACK OF CONVERGENCE IN GUIDANCE EARLY-MID PERIOD AND IMPROVED CLUSTERING THEREAFTER... WITH SOME CONSIDERATION FOR CONTINUITY FROM YDAY. TO REFLECT THESE IDEAS THE DAYS 3-5 SUN-TUE FCST STARTS WITH A 50/30/20 BLEND OF THE 00Z ECMWF/UKMET/ECMWF MEAN WITH DAYS 6-7 WED-THU ADJUSTING TO A 40/30/30 BLEND OF THE ECMWF/ECMWF MEAN/GEFS MEAN.
12Z UPDATE... NEW GUIDANCE INCLUDING THE ECMWF HAS COME INTO BETTER AGREEMENT WITH DAY 3 SUN PLAINS EVOLUTION WITH A BETTER DEFINED SFC REFLECTION THAN THE 00Z ECMWF. THE FINAL FCST INCORPORATES IDEAS FROM THE 12Z ECMWF/UKMET/CMC WITH THE GFS LESS FAVORED AS IT IS ON THE DEEP SIDE OF THE SOLN SPREAD. UNCERTAINTY REMAINS ABOUT AS HIGH AS BEFORE FOR THE REST OF THE FCST. THE UKMET/CMC HAVE TRENDED TOWARD THE GFS SCENARIO OF PULLING A SIGNIFICANT AMOUNT OF ENERGY SWWD INTO NWRN MEXICO BY DAY 5 TUE THUS LEADING TO A MORE PROGRESSIVE/EWD WRN ATLC SYSTEM. HOWEVER THE 12Z ECMWF MAINTAINS CONTINUITY... ALBEIT IN SLIGHTLY SLOWER FORM... TOWARD A MORE CONSOLIDATED NRN STREAM MID LVL SYSTEM THAT ULTIMATELY MAINTAINS AN EAST COAST SFC LOW ON THE WRN EDGE OF THE GUIDANCE SPREAD. SOME TIMING/DETAIL DIFFS ARE NOTED WITH UPSTREAM FEATURES WITH MORE DATA DESIRED BEFORE MAKING A CONFIDENT ADJUSTMENT. FOR DAYS 4-7 THE FULL EVALUATION OF LATEST SOLNS IN LIGHT OF SENSITIVITY OF THE FCST PATTERN FAVORS ONLY MINOR DETAIL ADJUSTMENTS TO THE UPDATED PRELIM ISSUANCE.
THE LARGE SCALE MEAN PATTERN SHOULD MAINTAIN WARM AND DRY CONDS OVER MOST AREAS WEST OF THE ROCKIES AND BELOW NORMAL TEMPS OVER THE ERN HALF OF THE LOWER 48. THE MOST EXTREME READINGS ARE FCST OVER THE NORTHEAST ON SUN-MON WHEN HIGHS MAY BE UP TO 15-25 F BELOW NORMAL. THERE IS STILL CONSIDERABLE UNCERTAINTY OVER THE EVENTUAL NWD EXTENT OF WINTRY PCPN SPREADING EWD FROM THE PLAINS SUN ONWARD... WITH POSSIBLE SCENARIOS OVER THE NORTHEAST BY TUE-WED RANGING FROM A MAJOR EVENT TO NO PCPN AT ALL. CURRENT FCST PREFERENCES ARE TOWARD HAVING AT LEAST SOME PCPN REACHING NERN AREAS. MEANWHILE DEPENDING ON THE DEGREE OF GULF INFLOW THERE MAY BE SOME LOCALLY MDT-HVY RNFL OVER EXTREME SRN AREAS. BEHIND THIS SYSTEM SOME LOCATIONS FROM THE NRN ROCKIES INTO THE GRTLKS/OH VALLEY MAY SEE ONE OR MORE DAYS OF LGT SNOW. THOUGH A LOW PROBABILITY SOLN AT THIS TIME... POTENTIAL EXISTS FOR SOME RESIDUAL SRN STREAM ENERGY TO GENERATE ANOTHER GULF OF MEXICO WAVE LATE IN THE PERIOD.
RAUSCH
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In this thread:
Heads up Fred -
JAC,
1/20/2011, 1:12 pm- GFS backs off a little this morning - JAC, 1/22/2011, 8:45 am
- FIM - JAC, 1/21/2011, 10:23 pm
- Re: FIM - Conclue, 1/22/2011, 12:09 am
- Re: Heads up Fred - Conclue, 1/21/2011, 5:44 pm
- Coming at ya Fred - JAC, 1/21/2011, 2:06 pm
- Re: Heads up Fred - Fred, 1/21/2011, 8:04 am
- Here we go - JAC, 1/21/2011, 7:55 am
- Re: Heads up Fred - Fred, 1/20/2011, 2:39 pm
- HPC has some confidence with this one - JAC, 1/20/2011, 3:13 pm
- Re: Heads up Fred - JAC, 1/20/2011, 3:04 pm
- 12Z Euro bombs it inside the benchmark - JAC, 1/20/2011, 1:40 pm
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