Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 070152
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST FRI MAR 6 2015

.SYNOPSIS...
BRISK AND COOL NORTHEASTERLY WINDS WILL CONTINUE TO PRODUCE RATHER
WET CONDITIONS ACROSS WINDWARD SLOPES THROUGH TONIGHT...ESPECIALLY
ON THE BIG ISLAND AND MAUI. WINDS WILL DECREASE DURING THE WEEKEND
AS A SURFACE RIDGE TO THE NORTH IS ERODED AND DISPLACED TOWARD THE
ISLANDS. DEEPER MOISTURE SOUTH OF THE BIG ISLAND MAY PUSH FAR ENOUGH
NORTH TO INCREASE RAINFALL OVER THE BIG ISLAND ON SUNDAY AND MONDAY
AND POSSIBLY AGAIN DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
THE ISLANDS HAVE BEEN SITTING WITHIN A TRANSITION ZONE BETWEEN A
STRONG...NEARLY STATIONARY...1039 MB SURFACE HIGH 1500 MILES TO THE
NORTHWEST OF KAUAI AND A NEARLY STATIONARY FRONT ABOUT 400 MILES TO
THE NORTHEAST OF THE BIG ISLAND. MOISTURE POOLED NEAR THE FRONT
CONTINUES TO GET CAUGHT UP IN THE BRISK LOW LEVEL NORTHEASTERLY
FLOW AND TRANSPORTED OVER THE EASTERN END OF THE ISLAND CHAIN.
SEVERAL WINDWARD GAUGES ON THE BIG ISLAND AND MAUI HAVE PICKED UP
OVER A HALF AN INCH ON RAINFALL DURING THE DAY...WHILE LESS THAN A
TENTH OF AN INCH HAS BEEN COLLECTED AT THE WETTEST WINDWARD GAUGES
ON THE WESTERN ISLANDS.  LEEWARD AREAS CONTINUE TO BE DRY...WITH THE
EXCEPTION OF A FEW SHOWERS ON THE BIG ISLAND.

IN THE SHORT TERM...EXPECT A GRADUAL DECREASE IN WINDWARD RAINFALL
ALONG WITH A DECREASE IN THE COOL NORTHEAST WINDS ON SATURDAY.
FORECAST MODELS ARE IN GOOD AGREEMENT THAT LOW LEVEL MOISTURE WILL
STICK AROUND MAUI AND THE BIG ISLAND TONIGHT THEN DRIFT OFF TO THE
EAST ON SATURDAY. AS A RESULT...EXPECT WET WINDWARD CONDITIONS FOR
THE BIG ISLAND AND MAUI TONIGHT FOLLOWED BY DECREASING SHOWERS ON
SATURDAY. FEWER WINDWARD SHOWERS ARE EXPECTED FROM MOLOKAI TO
KAUAI..AND LEEWARD AREAS WILL CONTINUE TO BE RATHER DRY. NORTHEAST
WINDS WILL BACK OFF ON SATURDAY AS THE SURFACE RIDGE TO THE NORTH IS
WEAKENED. DEW POINT TEMPERATURES WITHIN THE NORTHEAST FLOW WILL
REMAIN IN THE UPPER 50S AND LOWER 60S...MAINTAINING A COOL FEEL.

AN INCREASE IN RAINFALL IS EXPECTED FOR THE BIG ISLAND SUNDAY AND
MONDAY...WHILE ALL ISLANDS WILL SEE A DECREASE IN THE COOL
NORTHEASTERLY WINDS AND AN INCREASE IN HIGH CLOUDS. THE CURRENT
LONGWAVE PATTERN FEATURES DEEP TROUGHING JUST NORTH-NORTHEAST OF THE
STATE FLANKED BY DEEP RIDGING. A SHORTWAVE ALOFT WILL ROTATE THROUGH
THE BASE OF THE TROUGH LATE SUNDAY INTO EARLY MONDAY. THIS WILL
WEAKEN THE SURFACE RIDGE CURRENTLY TO OUR NORTH...LEADING TO A
DECREASE IN THE NORTHEAST WINDS. DEEPER MOISTURE WILL LIKELY BE
DRAWN OVER THE BIG ISLAND AND POSSIBLY AS FAR NORTH AS MAUI...
CREATING THE POTENTIAL FOR ANOTHER BOUT OF WET WEATHER AND SUMMIT
SNOWFALL ON THE BIG ISLAND...THOUGH NOT AS HEAVY OR PERSISTENT AS
THE LAST ROUND.

MODERATE NORTH TO NORTHEAST WINDS WITH LIMITED WINDWARD RAINFALL
WILL PERSIST FROM KAUAI TO MAUI THROUGH NEXT WEEK...WHILE ENHANCED
MOISTURE WILL LINGER NEAR THE BIG ISLAND. ANOTHER UPPER LEVEL TROUGH
SETTING UP OVER THE REGION COULD PULL THE MOISTURE BACK UP OVER THE
BIG ISLAND AND POSSIBLY MAUI SOMETIME TUESDAY NIGHT THROUGH
THURSDAY. GUIDANCE CONTINUES TO SHOW RATHER LOW DEW POINT
TEMPERATURES ALL THE WAY THROUGH THE END OF NEXT WEEK...SO EXPECT
THE COOL CONDITIONS TO PERSIST.

ANOTHER PROLONGED EPISODE OF VERY STRONG WINDS FOR THE BIG ISLAND
SUMMITS APPEARS LIKELY. STRONG WESTERLY WINDS HAVE BEEN AT BORDER
LINE WARNING STRENGTH AT THE CFHT GAUGE ON MAUNA KEA DURING THE PAST
COUPLE OF HOURS AND WILL LIKELY REMAIN WELL ABOVE ADVISORY LEVELS
FOR MAUNA LOA AND MAUNA KEA TONIGHT FOLLOWED BY A BRIEF DOWNWARD
TREND ON SATURDAY. WINDS WILL RATCHET BACK UP ON SATURDAY NIGHT AND
SUNDAY...POSSIBLY TO WARNING LEVELS...AS A SHORT WAVE ALOFT ROTATES
AROUND THE MID LEVEL TROUGH TO OUR NORTH AND PASSES OVERHEAD. THE
CURRENT WIND ADVISORY HAS BEEN EXTENDED THROUGH THE WEEKEND TO COVER
THE WINDIEST CONDITIONS...THOUGH STRONG SUMMIT WINDS COULD LINGER
INTO NEXT WEEK.

&&

.AVIATION...
BREEZY NORTHEAST WINDS WILL CONTINUE INTO SATURDAY BEFORE WEAKENING
SATURDAY EVENING. AIRMET TANGO FOR LOW LEVEL TURB OVER AND SOUTH
THROUGH WEST OF THE ISLANDS WILL REMAIN POSTED.

SHOWERS EMBEDDED WITHIN THE BREEZY FLOW WILL BRING PERIODS OF
LOWERED CIGS AND VIS...MAINLY TO THE WINDWARD SIDES OF ALL ISLANDS.
ANY PASSING SHOWERS OVER THE WESTERN END OF THE STATE SHOULD BE
RELATIVELY SHORT LIVED. ENHANCED MOISTURE LINGERS NEAR THE EASTERN
END OF THE STATE...ALLOWING FOR MORE PROLONGED SHOWER ACTIVITY
ESPECIALLY ALONG WINDWARD SLOPES. CLOUDS AND SHOWERS HAVE BANKED UP
ON MOUNTAIN SLOPES ON...MOLOKAI...MAUI...AND THE BIG ISLAND AND
THEREFORE AIRMET SIERRA FOR MTN OBSC CONTINUES.

THE VAD WIND PROFILE FROM THE PHWA RADAR...LOCATED AT SOUTH POINT
HAWAII...IS SHOWING RETURNS CORRESPONDING TO A LAYERED DECK
FROM 110 TO FL300. SATELLITE IMAGERY SUGGESTS THIS AREA IS JUST
SOUTH AND EAST OF THE BIG ISLAND...IN AND AROUND THE SOUTHEAST
COASTAL WATERS. LIGHT RIME ICING MAY OCCUR IN CLOUDS OF THIS DEPTH.
ELSEWHERE...THINNER CIRROSTRATUS...BETWEEN FL250 AND FL300...STREAM
OVER.

AIRMET TANGO FOR TEMPO LIGHT TO MOD TURB BETWEEN FL250 AND FL300 IS
POSTED AS AN UPPER LEVEL JET SITS OVERHEAD.

&&

.MARINE...
LOCALLY STRONG NE WINDS WILL CONTINUE THROUGH MOST OF SATURDAY AS A
STRONG RIDGE REMAINS ABOUT 300 NM N OF THE ISLANDS. A SMALL CRAFT
ADVISORY /SCA/ HAS BEEN EXTENDED THROUGH THE DAY ON SATURDAY FOR
AREAS WHERE THE LOW LEVEL FLOW IS ACCELERATED BY TERRAIN. THESE
AREAS WILL ALSO EXPERIENCE ROUGH SEAS AROUND 10 FT. THE RIDGE WILL
BEGIN TO WEAKEN ON SATURDAY...LEADING TO A GRADUAL DECLINE IN THE N
TO NE WINDS TO MODERATE STRENGTH BY SUNDAY.

MID PERIOD NORTHERLY SWELL WILL DOMINATE THROUGH THE MIDDLE OF NEXT
WEEK. A STAGNANT WEATHER PATTERN ACROSS THE PACIFIC IS FAVORING THE
AREA N AND NNE OF THE ISLANDS FOR LOW PRESSURE DEVELOPMENT. THESE
LOWS WILL BE SOMEWHAT CLOSE AND NOT VERY STRONG...RESULTING IN SHORT
TO MID PERIOD N SWELLS. A LARGER PULSE N SWELL COULD PRODUCE SURF
NEAR THE ADVISORY LEVEL ON MONDAY...BUT THERE COULD BE PERIODS OF
HARBOR SURGE AT HILO AND KAHULUI THIS WEEK. SEE THE COLLABORATIVE
NEARSHORE SWELL AND WIND FORECAST /SRDHFO/ FOR MORE DETAILS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 AM HST MONDAY FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST SATURDAY FOR KAUAI NORTHWEST
WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-OAHU LEEWARD WATERS-
KAIWI CHANNEL-MAUI COUNTY LEEWARD WATERS-MAALAEA BAY-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND
SOUTHEAST WATERS.


&&

$$
DISCUSSION/MARINE...WROE
AVIATION...EATON




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