Prognostic Meteorological Discussion
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FXAK02 KWNH 231851
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT THU OCT 23 2014

VALID 12Z MON OCT 27 2014 - 12Z FRI OCT 31 2014

IT IS DIFFICULT TO SAY TO WHAT EXTENT RECENT SATELLITE DATA INGEST
ISSUES MAY BE RESPONSIBLE BUT TIMING DIFFS WITH LARGE SCALE
SYSTEMS BECOME EVIDENT EVEN BEFORE THE START OF THE FCST PERIOD
12Z MON.  THESE DIFFS ARE ESSENTIALLY REFLECTED IN TWO CLUSTERS...
ONE COMPOSED OF LATEST GFS/GEFS RUNS THAT BECOME SLOWER WITH ERN
ASIA ENERGY ALREADY BY DAY 2 SAT IN TURN CAUSING BERING
SEA/ALEUTIANS TROUGH ENERGY TO BECOME SLOW/SHARP/AMPLIFIED BY DAYS
3-4 SUN-MON... VERSUS ANOTHER CLUSTER CONSISTING OF THE 00Z
ECMWF/ECMWF MEAN ALONG WITH 00Z CMC/UKMET/NAVGEM SOLNS WHICH ARE
MORE PROGRESSIVE WITH SIGNIFICANT FEATURES.

ECMWF MEAN CONTINUITY LEADING UP TO DAY 6 WED IS NOT SPECTACULAR
BUT AT LEAST BY THAT DAY THE PAST FOUR RUNS HAVE BEEN REASONABLY
CONSISTENT IN SHOWING THE CORE OF AN UPR TROUGH JUST S OF THE
PANHANDLE.  IN ADDITION MULTI-DAY MEANS AT D+8 FOR THE PAST COUPLE
DAYS HAVE GENERALLY BEEN SHOWING A CORE OF POSITIVE HGT ANOMALIES
OVER THE NRN PAC JUST SW THE MAINLAND... WITH TELECONNECTIONS
RECOMMENDING A MEAN TROUGH AXIS NOT FAR FROM THE PAC NW COAST.
BROAD CYCLONIC MEAN FLOW UPSTREAM OVER ASIA ALSO SEEMS TO FAVOR
DECENT PROGRESSION SO AS A STARTING POINT PREFER THE 00Z ECMWF
MEAN AS A BASE WITH SOME NON-GFS OPERATIONAL INPUT WHERE FEASIBLE.
 OVER THE NERN PAC THIS SOLN STILL PROVIDES BETTER OVERALL
CONTINUITY THAN ANY ALTERNATIVES.  ADJUSTMENTS ARE LESS AVOIDABLE
UPSTREAM.  THE 12Z UKMET/CMC STILL GENERALLY LEAN TOWARD A NON-GFS
SCENARIO WHERE MAJOR DIFFS EXIST BUT THE 12Z ECMWF HAS ADJUSTED IN
THE GFS DIRECTION SO CONFIDENCE REMAINS ON THE LOW SIDE.

A FURTHER UNCERTAINTY IN THE FCST IS ONGOING DIFFICULTIES THAT
MODELS/ENSEMBLES HAVE HAD IN RESOLVING THE PSBL INTERACTION
BETWEEN THE EXTRATROPICAL TRANSITION OF T.S. ANA AND AN
APPROACHING MID-LATITUDE PACIFIC SYSTEM... AND THEN IF THERE IS
ANY INTERACTION WITH THE HGT FALLS REACHING THE NERN PAC AS PER
THE FAVORED NON-GFS CLUSTER.  FOR NOW WILL HOLD BACK ON A NERN PAC
SYSTEM /OFFSHORE THE PANHANDLE/ AS DEEP AS THE PAST TWO ECMWF RUNS
OR 00Z UKMET AFTER 12Z DAY 5 TUE IN LIGHT OF GUIDANCE SPREAD...
AND A MUCH WEAKER SFC LOW IN THE 00Z CMC IN SPITE OF A MID LVL
EVOLUTION THAT IS SOMEWHAT SIMILAR TO THE 00Z ECMWF.  MOST SOLNS
CURRENTLY SUGGEST MINIMAL INTERACTION BETWEEN EXTRATROPICAL ANA
AND NERN PAC HGT FALLS... WITH A TRACK WELL S OF THE PANHANDLE
CLOSER TO VANCOUVER ISLAND.

ELSEWHERE... EXPECT STEADY NEWD PROGRESSION OF A SYSTEM NEAR THE
BERING STRAIT AS OF 12Z MON WHILE THE NEXT SYSTEM IN THE SERIES
TRACKS ACROSS THE NWRN BERING SEA FROM WED ONWARD AS PER THE 00Z
ECMWF MEAN/CMC MEAN.  THE 00Z GEFS MEAN COMPLETELY DAMPENED OUT
THIS SYSTEM LATER IN THE PERIOD BUT THE 06Z-12Z GEFS MEANS...
INITIALLY SLOW LIKE THE REST OF THE GFS CLUSTER... CATCHES UP TO
THE 00Z ECMWF/CMC MEANS BY NEXT THU.

RAUSCH

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