058
FXUS02 KWBC 021853
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
253 PM EDT FRI OCT 02 2009
VALID 12Z MON OCT 05 2009 - 12Z FRI OCT 09 2009
AN AMPLIFYING RIDGE EXTENDING FROM THE EASTERN PACIFIC INTO
EASTERN ALASKA AND NORTHWEST CANADA WILL ALLOW TROUGHING TO
PERSIST ACROSS HUDSON BAY AS WELL AS THE AMERICAN SOUTHWEST...WITH
RIDGING EXPECTED ACROSS THE SOUTHEAST. MANY DETAIL ISSUES ARE YET
TO BE WORKED OUT AS RUN-TO-RUN CONSISTENCY IS LACKING BY BOTH THE
GFS AND ECMWF. HOWEVER... THE 00Z ECMWF IS THE LEAST OF ALL EVILS
AMONG THE OPERATIONAL GUIDANCE BUT HAS ITS SHARE OF QUESTIONABLE
FEATURES.
THE LARGEST AREAS OF UNCERTAINTY LIE WITH SHORTWAVE ENERGY EXITING
THROUGH THE GREAT LAKES ON WED/D5 AND SUBSEQUENT ENERGY DROPPING
INTO WESTERN CANADA FROM BOTH ALASKA AND THE CANADIAN ARCTIC. THIS
PLACES THE 00Z ECMWF AND 00Z/06Z GFS 180 DEGREES OUT OF PHASE
ALONG 80W BY DAYS 6-7 AS THE ECMWF SHOWS RIDGING AHEAD OF A DEEP
TROUGH MOVING OUT OF THE ROCKIES WHILE THE GFS HAS A VERY BROAD
TROUGH ENCOMPASSING MOST OF CANADA EAST OF THE CANADIAN ROCKIES
AND FROM THE NORTHERN PLAINS TO NEW ENGLAND. BY WED/D7... THE
ENSEMBLE MEANS EITHER SHOW SLIGHT RIDGING... 00Z ECMWF ENS... OR
ZONAL FLOW... 00Z GEFS/CANADIAN/NAEFS ENS... BUT GENERALLY WITHOUT
A HUGE AMOUNT OF SPREAD. VARIOUS SPAGHETTI PLOTS SHOW THE 00Z GFS
/AND SIMILAR 06Z GFS/ AS AN OUTLIER IN MANY ASPECTS COMPARED TO
OTHER GFS/ECMWF/CANADIAN ENSEMBLE MEMBERS. 00Z CANADIAN AND 00Z
ECMWF ARE MORE IN LINE WITH THE GFS/ECMWF ENSEMBLE MEANS... BUT
THE 00Z CANADIAN SHOWS A SLOWER AND FARTHER WEST SOLUTION IN THE
CENTRAL PLAINS ON DAYS 4-5. BY DAYS 6-7... THE 00Z ECMWF APPEARS
TOO FAST TO BRING THE BASE OF THE WESTERN TROUGH EASTWARD OUT OF
THE SOUTHWEST GIVEN... 1/ ALL THE CONTINUED SUPPORT BY THE
ENSEMBLE MEMBERS /OF ALL MODELS/ TO KEEP SOMETHING BACK... AND 2/
A CLIMATOLOGICAL MAXIMUM IN CLOSED LOW FREQUENCY NEAR COASTAL
CALIFORNIA IN THE FIRST WEEK OF OCTOBER. THE 00Z CANADIAN HOLDS
THE TROUGH AXIS FARTHER WEST AS IT DIGS A CLOSED LOW INTO THE
BAJA.
USED MOSTLY THE 00Z/02 ECMWF FOR DAYS 3-5 BUT DID ADD A SMIDGEN OF
THE 00Z/01 ECMWF WHICH PAIRED WELL IN MANY INSTANCES. THE 12Z/01
ECMWF APPEARED QUITE OUT OF PLACE DUE TO ITS HANDLING OF ENERGY
PUSHING THROUGH ALASKA BY WED/DAY 5. FOR DAYS 6-7... THE 00Z ECMWF
ENSEMBLE MEAN WAS LARGELY USED TO TAME DOWN THE OPERATIONAL ECMWF
AND SLOW THE EXIT OF THE TROUGH IN THE SOUTHWEST. THE 00Z GEFS
MEAN WAS NOT TOO DIFFERENT OUTSIDE THE GREAT LAKES WHERE IT SHOWED
FLATTER FLOW.
12Z MODEL UPDATE... THE 12Z GFS REMAINS CLOSE TO ITS 00Z/06Z RUNS.
THE 12Z CANADIAN SHOWS A DEEP CUTOFF LOW SW OF SOCAL BY DAY 6 THE
12Z UKMET/GFS/GEFS MEAN SHOW A NEARLY EQUALLY AS DEEP CLOSED LOW
NEAR THE CA/AZ/NV INTERSECTION AND THE 12Z ECMWF HAS BROUGHT BACK
A DEEPER CLOSED LOW OVER SOCAL. IN THE EAST... THE 12Z GFS/ECMWF
SHOW A FLATTER FLOW OVER THE GREAT LAKES ON DAY 7 THAT WAS
ACCOUNTED FOR EARLIER BY WAY OF THE ECMWF ENSEMBLE MEAN. NO
CHANGES WERE MADE FOR THE FINAL PROGS... BUT THERE IS GROWING
SUPPORT FOR A DEEPER AND MORE LONG-LIVED CLOSED LOW NEAR
SOUTHERN/COASTAL CALIFORNIA AFTER WED/D5.
ROTH/FRACASSO
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