Prognostic Meteorological Discussion
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FXHW01 KWNH 291213
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
713 AM EST THU JAN 29 2015

VALID 00Z FRI JAN 30 2015 - 00Z FRI FEB 06 2015

UNSETTLED WEATHER IS EXPECTED ACROSS THE ISLANDS THIS WEEKEND WITH
BELOW NORMAL NIGHT TIME LOW TEMPERATURE READINGS.

THE 29/00Z ECENS/GEFS AND DETERMINISTIC RUNS SIGNAL PERSISTENT
SURFACE TROUGHING AND PERSISTENT `COLD ADVECTION` THROUGH DAY 5.
COLD ADVECTION BEING A RELATIVE TERM AT SUBTROPICAL
LATITUDES---BUT NONETHELESS. THE ECMWF...GFS AND CANADIAN
DETERMINISTIC RUNS INDICATED---ABOVE NORMAL BAROCLINICITY SURGING
ALONG/SOUTH OF 30N LATITUDE, AND MID-LEVEL SHORTWAVE ENERGY
PRODUCING SUB-SYNOPTIC SCALE WARM ADVECTION WITH DISTINCT WIND
SHIFTS---MORE CHARACTERISTIC OF MID-LATITUDE MIGRATORY WEATHER
SYSTEMS.

THE 29/00Z GFS/ECMWF ARE EQUALLY-AGGRESSIVE SOLUTIONS WITH THE
ARRIVAL OF THE INITIAL COLD FRONT---MOVING WEST TO EAST---ON
FRIDAY. THE 28/00Z GFS MIGRATES THE FRONT SOUTHWARD TO NEAR 20N
OVER THE WEEKEND---MAKING A FULL JOURNEY ACROSS THE ENTIRE STATE.
THE ECMWF STALLS THE FRONT OVER KAUAI---ALLOWING IT TO SETTLE NO
FURTHER EASTWARD THAN OAHU. THE CANADIAN, AN EVEN WEAKER SOLUTION.

AS WAS THE CASE YESTERDAY WHEN THE 28/00Z ECMWF FIRST CONSIDERED
SECONDARY WAVE ENERGY DEVELOPMENT INVOF 160W---THE 29/00Z FORECAST
CYCLE GUIDANCE SEEM TO BE IN SOMEWHAT BETTER AGREEMENT (IN
PRINCIPLE); WITH DEVELOPING A SURFACE REFLECTION AND LOW-LEVEL
WAVE INVOF 30N 165W ON/AROUND 2/12Z. IN TURN, THE LOW-LEVEL FLOW
ATTEMPTS TO SET UP A MORE DISTINCT SOUTH TO SOUTHWEST WIND---IN
TRUE MID-LATITUDE WARM ADVECTION FASHION. THIS FLOW PATTERN
DISRUPTING THE TRADES, AND ENCOURAGING A RELATIVELY-WET FLOW
"SETUP" FOR THE STATE FOR NEXT WEEK.

THERE ARE INDICATIONS THAT A PATTERN TRANSITION IS GOING TO TAKE
PLACE IN THE CENTRAL PACIFIC---DURING THE DAY 4-6 PERIOD. THIS WAS
NOTED YESTERDAY IN THE NORTH PACIFIC ALONG 35-45N 160W (SEE PMDAK
DISCUSSION) AS THE UPPER-LEVEL CYCLONE AND LONG WAVE SHIFTS
EAST-SOUTHEASTWARD AND AWAY FROM THE ALEUTIANS.

RECOMMEND A BLEND OF THE 29/00Z GEFS/ECENS FOR DAYS 5-7.
MEANWHILE, THE DETERMINISTIC GFS (29/00Z) SEEMED REASONABLE
THROUGH DAY 3, IF A MORE PESSIMISTIC APPROACH/PREFERENCE WAS IN
ORDER.

VOJTESAK


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