485
FXUS02 KWBC 161801
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
158 PM EDT SAT AUG 16 2008
VALID 12Z TUE AUG 19 2008 - 12Z SAT AUG 23 2008
SOME SHORT RANGE ISSUES REMAIN WITH ERN BERING SEA/NERN PACIFIC
FLOW... BUT COMPARED TO 24 HRS AGO THERE IS SOMEWHAT IMPROVED
CONSENSUS TOWARD A VIGOROUS TROF AND EMBEDDED CLOSED LOW REACHING
THE WEST COAST AROUND WED-THU. THIS FEATURE SHOULD THEN PROGRESS
EWD/NEWD THEREAFTER. SHORTLY BEFORE REACHING THE COAST THE 00Z
ECMWF... WHICH IS THE FARTHEST SWD SOLN WITH THE MID LVL LOW...
SHOWS SOME MID LVL HGTS THAT REACH 3-5 STANDARD DEVIATIONS BELOW
NORMAL. MEANWHILE THE GFS IS COMPARABLE TO THE UKMET THRU DAY
5/THU WHILE THE CANADIAN AND ENSEMBLE FAVOR A FARTHER NWD TRACK OF
THE CLOSED LOW. AS THE TROF CONTINUES INLAND... THE 00Z GFS
BECOMES MORE AMPLIFIED THAN MOST OTHER GUIDANCE WHICH INDICATES
EITHER GREATER NEWD PROGRESSION OF THE TROF OR REPLACEMENT OF THE
MEAN TROF WITH LESS AMPLIFIED FLOW UPSTREAM. ENOUGH UNCERTAINTY
EXISTS TO RECOMMEND AN INTERMEDIATE SOLN TO LEAN AWAY FROM THE
MORE EXTREME ASPECTS OF VARIOUS MODELS. THERE IS REASONABLE
AGREEMENT THAT THIS TROF SHOULD EVENTUALLY PICK UP THE ENERGY
CONTAINED WITHIN THE MID LVL LOW THAT SHOULD BE OVER THE SRN
PLAINS AS OF TUE.
WITH THE TROF EXPECTED TO AFFECT THE NORTHEAST DURING THE FIRST
HALF OF THE PERIOD... THERE IS STILL CONSIDERABLE SPREAD AMONG
MODELS AND ENSEMBLE MEMBERS LEADING TO ONLY MODERATE CONFIDENCE AT
BEST. GFS RUNS HAVE BEEN CONSISTENTLY PROGRESSIVE AND GEFS MEANS
HAVE TRENDED FASTER TOWARD THE GFS SOLNS OVER THE PAST DAY... BUT
REMAINING GUIDANCE STILL SUGGESTS THE TROF WILL BE SLOWER/MORE
AMPLIFIED THAN THE GFS. THE LARGE SCALE PATTERN APPEARS FAVORABLE
ENOUGH TO ALLOW FOR A SLOWER TROF THAN FCST BY THE GFS... THOUGH
SOME ECMWF/CANADIAN RUNS HAVE PROBABLY BEEN SOMEWHAT EXTREME.
12Z GFS MUCH SLOWER EJECTING THE ERN CANADIAN TROF THAN THE 00Z
RUN AND MUCH CLOSER IN AGREEMENT WITH THE ECMWF DAYS 3-5 TUE-THU.
IT IS ALSO SLIGHTLY WEAKER AND FASTER MOVING THE STRONG EPAC/NW
COAST TROF AND CLOSED LOW ACROSS THE NRN PLAINS DAYS 6 AND 7
FR-SAT MUCH MORE IN LINE WITH ECMWF ENS MEAN. BY DAY 8 SUN IT
TAKES AN AMPLIFIED TROF EWD ACROSS THE NRN PLAINS/UPPER MS VALLEY
INTO THE GREAT LAKES REGION AND THIS IS A FAIR MATCH TO BOTH GFS
AND ECMWF ENS MEANS FROM THE 00Z RUN.
SEE LATEST TPC ADVISORY FOR INFORMATION REGARDING TROPICAL STORM
FAY FCST TO STRENGTHEN TO A HURRICANE AS IT TRACKS JUST W OF THE
FL PENINSULA BY TUE AND THEN WEAKEN AS IT PROGRESSES INTO THE SERN
CONUS WED ONWARD. DAYS 5-7 FCST EXTRAPOLATES THE CURRENT TPC
TRACK NWD BASED ON MOVEMENT AROUND THE WRN PERIPHERY OF A DEEP
LAYER RIDGE OVER THE WRN ATLC/EAST COAST.
A BLEND OF 00Z ECMWF AND ECMWF MEAN USED THRU THE PERIOD FOR THE
LARGE SCALE PATTERN WITH
ADJUSTMENTS MADE TO ACCOMMODATE TPC TRACK FOR T.S. FAY.
RAUSCH/ROSENSTEIN
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