095
FXUS02 KWBC 301929
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
328 PM EDT FRI OCT 30 2009
VALID 12Z MON NOV 02 2009 - 12Z FRI NOV 06 2009
IN GENERAL...A MIDLATITUDE TROUGH IN THE EASTERN PACIFIC IS
EXPECTED TO AMPLIFY VCNTY OF 150W MON-TUE DAYS 3-4....THEN THE SRN
PORTION OF THE TROF IS LIKELY TO SPLIT OFF INTO AN UPPER LOW. A
SLOWLY PROGRESSIVE RIDGE WILL DRIFT EWD ACROSS THE SRN ROCKIES TO
THE HIGH PLAINS DURING THE PERIOD. BROAD DOWNSTREAM TROFFING IS
EXPECTED VCNTY OF 80W BY TUE-THU DAYS 4-6. HOWEVER...UNCERTAINTY
DEVELOPING UPSTREAM LOWERS OUR CONFIDENCE IN THE PATTERN OVER THE
ENTIRE COUNTRY BY FRI DAY 7. HIGH SPREAD OFFSHORE IN THE PACIFIC
IS EXPECTED TO WORK ITS WAY EWD ACROSS THE LOWER 48 STATES THE
LATTER HALF OF NEXT WEEK...GIVEN THE RATHER FAST FLOW ACROSS THE
COUNTRY.
THE LATEST ENSEMBLE SPAGHETTI PLOTS RE-ENFORCED YESTERDAYS IDEA OF
HIGH ENSEMBLE SPREAD DEVELOPING WELL OFFSHORE THE W COAST OF THE
CONUS BY EARLY WED DAY 5. NEW 12Z MODELS BEGIN TO SHOW A WIDE
RANGE OF SOLUTIONS LATER TUE DAY 4 ALONG 150W CONCERNING HOW
ENERGY SPLITS OFF THE SRN PORTION OF THE PACIFIC TROF INTO A
CLOSED LOW...WITH UNCERTAINTY IN THE NRN PORTION OF THE SPLIT
ACROSS THE GULF OF ALASKA. THE 12Z/30 DETERMINISTIC GFS IS ON THE
SW EDGE OF THE ENVELOPE OF SOLUTIONS WITH ITS CLOSED LOW...HEADING
TOWARDS THE N SIDE OF HAWAII. MEANWHILE THE 00Z/30
GFS/UKMET/CANADIAN WERE MORE ON THE N CENTRAL SIDE OF THE SOLUTION
ENVELOPE BY WED DAY 5.
12Z/30 MODELS WERE STILL QUITE DIVERGENT WITH THEIR UPPER LOW
POSITIONS WED DAY 5 AND BEYOND. HOWEVER THE NEW 12Z/30 GEFS MEAN
GAVE US CONFIDENCE TO STAY THE COURSE. FINAL PROGS STAYED WITH THE
50-50 BLEND OF THE GFS AND GEFS MEAN USED IN THE EARLIER PRELIM.
WITH THE PACIFIC UPPER LOW...THE 12Z/30 GEFS MEAN WAS SW OF OUR
EARLIER 500MB PROG WED/THU DAYS 5-6...BUT OTHERWISE HAD VERY GOOD
CONTINUITY FROM THE 00Z/30 GFS/GEFS MEAN BLEND THAT WAS USED FOR
THE PRELIM. THE NEW 12Z ECMWF/CANADIAN/UKMET AND GEFS ENSEMBLE
MEAN ARE IN GENERAL AGREEMENT IN CLUSTERING ON AN UPPER LOW
POSITION THU DAY 6 THAT IS NOT TOO DIFFERENT FROM OUR EARLIER THU
DAY 6 500MB PROG.
AGAIN TODAY...WE ARE EXPECTING A RATHER QUIET PERIOD AS REGARDS TO
SENSIBLE WEATHER AFTER A VERY ACTIVE OCTOBER. AS CONCERNS THE
BROAD TROFFING OVER THE ERN CONUS...THERE IS AN OVERALL
CONSENSUS TOWARD SLIGHTLY HIGHER AMPLITUDE BUT SHORTWAVES MOVING
THRU THE BROAD ERN TROF ARE LOW CONFIDENCE FEATURES.
FLOOD
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