ALASKA EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
200 PM EST SAT NOV 07 2009
 
VALID 12Z WED NOV 11 2009 - 12Z SUN NOV 15 2009
 
SYNOPTIC PATTERN SHIFT TOWARD BELOW NORMAL HEIGHTS REMAINS REMAINS
IN THE MEDIUM RANGE FORECAST OVER ALASKA BY THE END OF NEXT WEEK.
RELATIVE MEASURE OF PREDICTABILITY VALUES INCREASE OVER TIME AS
THE UPPER LOW SETTLES IN NEAR 65N/160W BUT THE INTERMEDIATE
EVOLUTION OF A COUPLE SYSTEMS CONTINUES TO VARY AMONG THE MODELS. 

THE TREND APPEARS TO BE TOWARD A SLOWER PROGRESSION OVERALL BUT
THE OPERATIONAL MODELS DISAGREE OVER WHETHER TO PHASE ENERGY NEAR
BRISTOL BAY OR KEEP A MORE SEPARATE FLOW. THE 12Z GFS IS ON THE
LEFT/WEST/PHASED SIDE WHILE THE 00Z ECMWF IS ON THE
RIGHT/EAST/UNPHASED SIDE BUT STILL DEVELOPS A 955MB LOW IN THE
GULF BY FRI/D6 AS A RESULT OF A DIFFERENT/LATER SHORTWAVE FROM THE
CENTRAL PACIFIC. ENSEMBLE MEANS SEEM TO FOCUS LOW PRESSURE NEAR
THE BERING STRAIT THEN TRANSLATE IT TO THE GULF... WHICH IS
GENERALLY AGREED ON BY THE OPERATIONAL MODELS. DID NOT WANT TO
JUMP TO THE DEEP SOLUTIONS SEEN BY THE CANADIAN AND GFS BUT FELT
PHASING OF SOME SORT WAS IN THE CARDS. THE 00Z AND LATEST /BUT TOO
LATE TO USE/ 12Z UKMET OFFERED A MORE MIDDLE GROUND FORECAST
NEARER TO THE ENSEMBLE MEAN EVOLUTION AND WAS EXPECTEDLY SLOWER
THAN THE FORECAST 24 HRS AGO. 07/00Z ENSEMBLE LOW CLUSTERING WAS
NOT AVAILABLE AND THE 06/12Z PLOTS WERE NOT TOO TELLING. LOTS OF
SPREAD EXISTS NEAR THE BERING STRAIT IN THE PMSL FIELD AND TO A
LESSER EXTENT SOUTH OF KODIAK. 

THE SYSTEM SHOULD MAKE A STEADY PROGRESSION INTO CANADA BY NEXT
WEEKEND LEAVING THE UPPER LOW OVER THE INTERIOR AND THE SFC LOW IN
THE GULF. ECMWF/CANADIAN AND SOME GFS RUNS WANT ANOTHER SYSTEM BY
SAT-SUN/D7-8 BUT NOT ENOUGH CONFIDENCE THERE YET TO DEPICT MORE
THAN WEAK LOW PRESSURE SOUTH OF THE ALEUTIANS. 

THE 00Z UKMET OFFERED A GOOD BASE FOR THE FORECAST THROUGH ABOUT
00/13 BEFORE IT BOMBED THE LOW DOWN TO 951MB. BROUGHT IN THE 06Z
GEFS AND 12/06 ECMWF ENSEMBLE MEAN FOR THE REST OF THE FORECAST.
THE 00Z/07 ECMWF ENSEMBLES WERE NOT AVAILABLE TODAY. IN-HOUSE
PARALLEL GFS RUN FOLLOWED THE OPERATIONAL GFS THROUGH ABOUT THU/D5
BUT THEN WAS SLOWER WITH THE FRONT HEADED TOWARD THE COAST /JUST A
BIT SLOWER THAN THE GOING FORECAST/. 

THE LATEST 12Z ECMWF HAS JUMPED TO A MORE PHASED SOLUTION BUT
MAINTAINS A VERY PROGRESSIVE FRONT THROUGH THE GULF BY FRI/D6. 

FRACASSO