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Hawaiian Islands Synoptic Discussion and Guidance

447
FXHW60 PHFO 010155
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST TUE MAR 31 2015

.SYNOPSIS...
A LOW LEVEL TROUGH NEAR KAUAI IS EXPECTED TO DISSIPATE OVER THE
WESTERN ISLANDS THIS EVENING. THIS WILL ALLOW LOCALLY STRONG TRADES
TO RETURN TO ALL AREAS WEDNESDAY. TRADE WIND CONDITIONS WILL PERSIST
INTO THE WEEKEND WITH SHOWERS FAVORING THE WINDWARD AND MOUNTAIN
AREAS.

&&

.DISCUSSION...
AS OF 3 PM HST...THE AFTERNOON CONVECTION ON KAUAI HAS BE SPOTTY AT
BEST AND CONFINED TO MAINLY THE SOUTHERN HALF OF THE ISLAND. THE
NORTHERN HALF IS PARTLY SUNNY AND MAINLY DRY. ON OAHU...IT HAS BEEN
SPOTTY AS WELL...FAVORING THE WAIANAE AND KOOLAU MOUNTAINS AND
WINDWARD COAST. LANAI HAD A HEAVY SHOWER OR TWO A SHORT TIME AGO
WHILE MOLOKAI AND MAUI HAVE BEEN GENERALLY QUIET...MAY BE A BRIEF
SHOWER OR TWO AT BEST. IN SHORT...SHOWER ACTIVITY IS SOMEWHAT LESS
THAN EXPECTED.

OTHER NOTEWORTHY OBSERVATIONS AS OF 230 PM HST...WIND DATA STATEWIDE
SHOWS THE EXTENT OF THE LIGHT AND VARIABLE WINDS AFFECTING MORE
ISLANDS THAN EXPECTED...REACHING OUT TO MOLOKAI AND WEST MAUI.
ALSO...THE AFTERNOON CLOUDS HAVE REACHED THE TWO SUMMITS ON THE BIG
ISLAND INCLUDING A BRIEF SHOWERS ON THE NORTHWEST SIDE OF MAUNA LOA.
SO ADJUSTMENTS HAVE BEEN MADE TO THESE AREAS. INCLUDING A SLIGHT
CHANCE FOR A SHOWER FOR THE SUMMITS FOR THE REST OF THIS AFTERNOON.

ALTHOUGH DIFFICULT TO PIN POINT BUT WE ARE PLACING THE LOW
LEVEL TROUGH OVER KAUAI THIS AFTERNOON AS PER GFS SOLUTION. IT IS
FORECAST TO EASE INTO THE KAUAI CHANNEL SHORTLY AND DISSIPATE THERE
EARLY THIS EVENING.

WATER VAPOR IMAGERY SHOWS THUNDERSTORMS CONTINUING OVER THE OFFSHORE
WATERS NORTH OF MOLOKAI AND MAUI. AN UPPER LEVEL SHORT WAVE TROUGH
IS THE RESPONSIBLE FEATURE FOR THESE STORMS. THE TROUGH IS MOVING
EAST AT 25 MPH...AND AT THIS RATE...PUTS THE UPPER TROUGH JUST EAST
OF THE BIG ISLAND AT 8 PM HST THIS EVENING. SO WITH THE UPPER TROUGH
LIFTING OUT...THE LOW LEVEL TROUGH FILLING...THE LOSS OF DAYTIME
HEATING...AND THE LACK OF SHOWERS...WE ANTICIPATE ANY REMAINING
SHOWERS TO END SHORTLY AFTER THE SUN SETS. IT IS A PRETTY DRY
EASTERLY WIND FLOW EAST OF MOLOKAI AS WELL. SO EXPECT A MAIN DRY
NIGHT ALL AREAS TONIGHT. ANY TRADE SHOWERS WILL LIKELY COME WELL
AFTER MIDNIGHT. EXPECT MORE TRADE SHOWERS FROM WEDNESDAY NIGHT ON.
THE REST OF THE FORECAST REMAINS INTACT WITH STRENGTHENING TRADES
REACHING LOCALLY STRONG OVER THE WATERS AROUND MAUI AND SOUTH OF THE
BIG ISLAND BY WEDNESDAY AFTERNOON. THE TRADES ARE EXPECTED TO SLIP
TO MODERATE SPEEDS FROM FRIDAY ON.

THERE REMAINS SOME DISCREPANCY BETWEEN THE EC AND GFS THURSDAY NIGHT
THROUGH SATURDAY WITH THE GFS BRINGING LIGHTER WINDS OVERALL AND
INCREASED MOISTURE TO THE BIG ISLAND. WE ARE CURRENTLY RIDING THE EC
SOLUTION AND CLIMATOLOGY WITH CONTINUED MODERATE TRADES INTO THE
WEEKEND.

&&

.AVIATION...
AIRMET SIERRA IS IN PLACE FOR ALL OF THE ISLANDS BUT SHOULD BE
LIFTED SOMETIME EARLY THIS EVENING. IT SHOULD BE A RELATIVELY
AIRMET-FREE NIGHT OTHERWISE.

&&

.MARINE...
WINDS WILL REMAIN BELOW SMALL CRAFT ADVISORY /SCA/ SPEEDS THROUGH
TONIGHT. TRADES ARE EXPECTED TO RETURN TO KAUAI AND OAHU BY DAYBREAK
WEDNESDAY AS THE TROUGH NEAR KAUAI AND OAHU DISSIPATES THIS EVENING.
THE TRADES WILL CONTINUE TO STRENGTHEN INTO WEDNESDAY REACHING
LOCALLY STRONG SPEEDS BY THE AFTERNOON...AND A SCA...FOR WATERS
AROUND MAUI AND SOUTH OF THE BIG ISLAND.

THE CURRENT SMALL NORTHWEST SWELL WILL DISSIPATE BY WEDNESDAY. A
SMALL SOUTH-SOUTHEAST SWELL WILL ALSO BE ON A GRADUAL DECLINE OVER
THE NEXT COUPLE OF DAYS...FOLLOWED BY A SMALL SOUTH-SOUTHWEST SWELL
FOR THE SECOND HALF OF THE WORK WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION...LAU







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