125
FXUS02 KWBC 231743
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
143 PM EDT FRI OCT 23 2009
VALID 12Z MON OCT 26 2009 - 12Z FRI OCT 30 2009
THE MANUAL PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7
WERE CONSTRUCTED USING A BLEND OF THE 00Z/23 ECMWF AND 12Z/22 EC
ENSEMBLE MEAN EARLY IN THE PERIOD...SWITCHING TO THE 00Z/23 GFS
AND 12Z/22 EC MEAN FROM ABOUT DAY 5 ONWARD. THE GEM GLOBAL AND
ECMWF STAND IN STARK CONTRAST TO THEIR MEANS FROM THE 12Z/22
CYCLE...WITH THE DETERMINISTIC ECMWF SHOWING ONE OF THE MOST
DRAMATIC FLIP FLOPS IN RECENT MEMORY SINCE ITS LAST RUN. BECAUSE
OF THE INSTABILITY AND SPREAD IN THE MODELS... WENT WITH THE MOST
RELIABLE GUIDANCE...THE EC ENSEMBLE MEAN...USING THE DETERMINISTIC
MODELS THAT MOST CLOSELY APPROXIMATED IT TO ADD SOME FIBER TO THE
DILUTED FIELDS. WHETHER THE FLOW SPLITS AS FEROCIOUSLY AS SOME OF
THE NEW DETERMINISTIC MODELS INDICATE IS UNCLEAR...AND THE
LOCATIONS OF THE SPLIT ARE LIKELY TO WILDLY FLUCTUATE IN THE DAYS
TO COME. SHOULD BE AN INTERESTING PERIOD FOR MEDIUM RANGE
FORECASTING.
UPDATED MORNING PRELIMS HAVE THE 06Z GFS AND 00Z ECMWF ENSEMBLES
TO EVALUATE. 06Z GFS FOLLOWS CLOSELY THE 00Z GFS BRINGING EWD THE
FULL LATITUDE TROF DAYS 6 AND 7 THU/FRI. OTHER AVAILABLE OP MODELS
SND ENS MEANS OF BOTH GFS AND ECMWF DO NOT SUPPORT THIS
PROGRESSION. PREFERENCE IS TOWARDS A BLEND OF OP ECMWF WITH
MAJORITY OF THE SOLUTION GFS/ECMWF ENS MEANS THROUGH THE PERIOD.
THIS HOLDS BACK THE TROF AND CLOSED LOW IN THE FOUR CORNERS REGION
DAY 6 THURSDAY WITH SLOW PROGRESSION FRIDAY. THIS IS A WESTWARD
ADJUSTMENTS OF PLAINS FRONTS FROM DAYS 4-7.
..AFTN FINALS
CURRENT MJO PHASE AND FORECASTS INDICATE A PHASE 8 TO PHASE 1
WHEELER DIAGRAM SOLUTION WHICH INDICATE HOLDING ON TO ERN CONUS
RIDGING AND A TROF/LOWER HTS FROM THE CENTRAL CANADIAN PLAINS INTO
THE SOUTHWEST DURING THIS FORECAST PERIOD.
12Z GFS TREND DAYS 3-5 LOOKS GOOD AS IT AMPLIFIES THE DIGGING WRN
TROF IN THIS PERIOD JOINING THE CONSENSUS OF OTHER MODELS. VAST
DIFFERENCES OCCUR IN THE CENTRAL AND ERN PACIFIC BRINGING LOW
PRESSURE AND A DEEP MID LEVEL EWD TO THE B.C. ABOUT 1000 NM EWD OF
PRIOR GFS RUNS BY DAYS 6 AND 7 AS IT DEEPENS A MID LEVEL TROF IN
THE GLFAK. THIS IS AN UNACCEPTABLE PROGRESSIVE DOWNSTREAM SOLUTION
OVER CONUS. LATEST 12Z CMC AND UKMET MAINTAIN THE DEEP WRN TROF
AND CLOSED LOW AT DAY 6 AND KEEP RIDGING OVER COASTAL B.C. HPC
PROGS AT THE SFC AND H500 WILL REMAIN THE SAME AS THE UPDATED
PRELIMS
SHORTER RANGE PORTION OF THE PERIOD DAYS 3-5 HAS LARGE QPF
DIFFERENCES OVER ERN CONUS WITH 00Z GFS/CMC BEING THE MORE
PROGRESSIVE KEEPING HVY RAINFALL OFFSHORE OF THE SOUTHEASTERN
SEABOARD WHILE 00Z ECMWF/NOGAPS/UKMET OFFER MUCH WETTER WESTWARD
CONDITIONS. PREFERENCE IS TOWARDS A MORE DIGGING WRN CONUS TROF
WHICH SHOULD HOLD ON TO ERN CONUS/W ATLC RIDGING WITH MORE SWRLY
FLOW KEEPING A COASTAL FRONT AND WAVE POTENTIAL FARTHER WEST THAN
00Z GFS/00Z CMC DAY 4.
COLD AMPLIFYING WRN TROF TUES-WED WILL BRING UPSLOPE SNOWS INTO
THE ROCKIES POSSIBLY HVY THEN BREAKING OUT EWD AS WIDESPREAD
FRONTAL PCPN FROM THE SWRN HIGH PLAINS NEWD INTO THE UPPER MS
VALLEY THURS WITH AN EWD PROGRESSION INTO THE PLAINS AND MS VALLEY
DAY 7 FRI.
WESTWARD THE AMPLIFIED MID LEVEL TROF AND CLOSED LOW DROPPING INTO
THE SOUTHWEST WILL INDUCE A BROAD AREA OF LOWER PRESSURE FROM ERN
CO TO SRN CAL. THIS COMBINED WITH PAC HIGH PRESSURE BUILDING INTO
THE INTERMTN REGION TUES-FRI WILL PROVIDE A BROAD OFFSHORE WIND
EVENT OVER THE CENTRAL/SRN INTERMTN REGION/AND CA WITH SANTA ANA
WIND EVENT POTENTIAL.
CISCO/ROSENSTEIN
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