203
FXHW01 KWNH 230802
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 AM EST SAT JAN 23 2021
VALID 00Z SUN JAN 24 2021 - 00Z SUN JAN 31 2021
LATEST MODELS AND ENSEMBLES CONTINUE TO DEPICT A SIMILAR PATTERN
EVOLUTION THROUGH THE PERIOD. STRONG HIGH PRESSURE TO THE
NORTH/NORTHEAST OF THE STATE, PERIODICALLY REINFORCED BY UPSTREAM
HIGH CENTERS, WILL MAINTAIN BRISK TO STRONG EASTERLY/SOUTHEASTERLY
WINDS FOR MOST OF THE PERIOD. RAINFALL WILL FOCUS OVER WINDWARD
AND MOUNTAIN LOCALES BUT SOME ACTIVITY COULD STRAY TO OTHER AREAS
AS WELL. FROM THE WEEKEND INTO THE FIRST HALF OF NEXT WEEK
GUIDANCE CONTINUES TO SHOW THE NORTHWESTWARD TRANSPORT OF ENHANCED
MOISTURE TOWARD/ACROSS THE ISLANDS IN RESPONSE TO FLOW BETWEEN A
DEVELOPING UPPER/SURFACE SYSTEM JUST WEST OF 170W LONGITUDE AND
THE DEEP-LAYER RIDGE TO THE NORTH/NORTHEAST OF THE STATE.
REPOSITIONING OF THE UPPER RIDGE SHOULD HELP TO PUSH DRIER AIR
INTO THE REGION FROM MIDWEEK ONWARD.
ALTHOUGH GUIDANCE AGREES ON THE GENERAL SCENARIO, THERE ARE STILL
SIGNIFICANT DIFFERENCES IN THE MAGNITUDE OF RAINFALL TOTALS
ASSOCIATED WITH NEXT WEEK'S MOISTURE SURGE. THESE DIFFERENCES ARE
MOST PRONOUNCED OVER THE NORTHWESTERN ISLANDS WHILE THERE IS
BETTER AGREEMENT IN PRINCIPLE FOR SOME LOCALLY HEAVY RAINFALL OVER
THE BIG ISLAND. GFS RUNS (WITH SUPPORT IN PRINCIPLE FROM THE GEFS
MEAN THOUGH OF COURSE WITH LIGHTER VALUES) CONTINUE TO BE HEAVIEST
OVER THE NORTHWESTERN ISLANDS WITH LATEST ECMWF/UKMET/CMC RUNS ALL
SUGGESTING THAT THE AXIS OF HEAVIEST RAINFALL SHOULD LIE FARTHER
WEST. THIS DIFFERENCE CORRESPONDS TO THE GFS/GEFS BEING WEAKEST
WITH THE UPPER RIDGE TO THE NORTH OF THE STATE AND ALLOWING FOR
LOWER SURFACE PRESSURES OVER/SOUTHWEST OF THE ISLANDS. THE
GUIDANCE COMPARISON FOR MASS FIELDS WOULD SUPPORT HEDGING SOMEWHAT
AWAY FROM THE GFS/GEFS SCENARIO. ON THE OTHER HAND GUIDANCE AS A
WHOLE HAS TRENDED HIGHER WITH PRECIPITABLE WATER VALUES OVER THE
PAST 24 HOURS. THE 00Z ECMWF IS ONCE AGAIN BETWEEN THE HIGHEST
00Z GFS AND SOMEWHAT LOWER 00Z GEFS/12Z ECMWF MEANS. THE HIGHER
TREND FOR MOISTURE OFFERS POTENTIAL FOR AT LEAST LOCALLY HEAVIER
AMOUNTS THAN WHAT THE NON-GFS CLUSTER IS ADVERTISING.
RAUSCH
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