359 
FXHW60 PHFO 302000
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST MON DEC 30 2013

.SYNOPSIS...
MOIST AND UNSTABLE CONDITIONS WILL MAINTAIN THE THREAT FOR HEAVY 
SHOWERS AND THUNDERSTORMS OVER THE BIG ISLAND TODAY...WHILE A RATHER 
STABLE NORTHEASTERLY FLOW PREVAILS ACROSS THE REST OF THE STATE. 
IMPROVING CONDITIONS ARE IN STORE ON THE BIG ISLAND TONIGHT AS A 
MODERATE TRADE WIND FLOW SPREAD OVER THE ENTIRE STATE. WINDS WILL 
BECOME SOUTHERLY ON NEW YEARS DAY...FOLLOWED BY THE PASSAGE OF A 
COLD FRONT ON FRIDAY.

&&

.DISCUSSION...
UNSETTLED WEATHER WILL CONTINUE ON THE BIG ISLAND TODAY...WHERE A 
FLASH FLOOD WATCH IS IN EFFECT. MOISTURE FROM A DISSIPATED FRONT IS 
POOLED OVER THE BIG ISLAND...AND A SHARP...SLOW-MOVING UPPER LEVEL 
TROUGH IS LOCATED JUST TO THE WEST. THIS COMBINATION HAS BEEN 
PRODUCING PERIODS OF HEAVY SHOWERS AND THUNDERSTORMS...SOME STRONG 
WITH HAIL...OVER WINDWARD BIG ISLAND FOR THE PAST DAY. A SPECIAL 
SOUNDING TAKEN AT 7000 AM HST AT HILO SHOWS PRECIPITABLE WATER 
VALUES OF 1.81 INCHES AND COLD AND UNSTABLE CONDITIONS ALOFT. SINCE 
THE UPPER TROUGH WILL INCH SLOWLY ACROSS THE BIG ISLAND TODAY...THE 
INSTABILITY WILL HANG ON...AND HEAVY SHOWERS AND THUNDERSTORMS COULD 
POP UP JUST ABOUT ANYWHERE. THE GROUND IS SATURATED ACROSS MUCH OF 
WINDWARD BIG ISLAND...SO IT WON/T TAKE MUCH ADDITIONAL HEAVY 
RAINFALL TO PRODUCE MORE FLOODING. THUS...A FLASH FLOOD WATCH HAS 
BEEN ISSUED.

IN STARK CONTRAST...A RATHER STABLE NORTHEASTERLY LOW LEVEL FLOW IS 
IN PLACE ACROSS THE REST OF THE STATE. THE OVERNIGHT LIHUE SOUNDING 
REVEALED A SOLID INVERSION AROUND 6000 FT WITH PRECIPITABLE WATER 
VALUES NEAR 0.9 OF AN INCH. CLOUDS AND LIGHT SHOWERS ARE PILED UP ON 
WINDWARD SLOPES FROM MAUI TO KAUAI...WHILE LEEWARD SECTIONS ARE 
MOSTLY CLEAR.

IMPROVING CONDITIONS ARE EXPECTED ON THE BIG ISLAND TONIGHT. THE 
UPPER LEVEL TROUGH AXIS WILL PUSH EAST OF THE STATE...BRINGING AN 
INCREASE IN STABILITY THAT SHOULD SHUT DOWN THUNDERSTORM ACTIVITY. 
REBUILDING TRADE WINDS WILL KEEP WINDWARD SLOPES A BIT WET...BUT 
HEAVY SHOWERS ARE NOT IN THE FORECAST.

BY TUESDAY...A RATHER STABLE...LIGHT TO MODERATE TRADE WIND FLOW 
WILL BRIEFLY TAKE OVER STATE-WIDE. RIDGING ALOFT WILL BE IN 
CONTROL...LIMITING SHOWERS TO WINDWARD SLOPES AS WELL AS LEEWARD BIG 
ISLAND SLOPES IN THE AFTERNOON. TRADE WINDS WILL BE ON A RAPID 
DECLINE ON NEW YEARS EVE.

WEDNESDAY AND THURSDAY WILL FEATURE A STRENGTHENING SOUTHERLY AND 
SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING FRONT. THE FRONT WILL 
SWEEP DOWN THE ISLAND CHAIN THURSDAY NIGHT AND FRIDAY.

&&

.AVIATION...
+RA/TSRA WILL CONTINUE OVER THE BIG ISLAND NE WINDWARD SLOPES THRU 
22Z WITH FREQUENT MVFR/IFR CONDITIONS. ADDITIONAL TSRA/+RA WILL 
DEVELOP OVER THE LEEWARD SLOPES AFT 22Z. AREAS OF MVFR/IFR 
CONDITIONS IS LIKELY WITH CB TOPS FL250-400. ELSEWHERE VFR WILL 
PREVAIL WITH ISOL MVFR CONDITIONS FOCUSED ON WINDWARD SECTIONS. 
AIRMETS FOR SIERRA TANGO AND ZULU ARE ALL IN EFFECT FOR THE 
RESPECTIVE HAZARDS...MAINLY OVER THE FAR ERN PORTION OF THE FA. 
PLEASE SEE THE AIRMETS FOR GREATER DETAIL.

SIGMET NOVEMBER REMAINS IN EFFECT FOR CAT ALOFT OVER THE ERN PORTION 
OF THE STATE AND ADJ WTRS. THE SIGMET AREA EXTENDS 900 NM SW AND 
WILL LIKELY AFFECT SOUTHBOUND HIGH LVL TRAFFIC. 

&&

.MARINE...
THE NORTHWEST SWELL IS ON A DECLINE. TRENDS AT BUOY 51101 AND 
MORNING SURF OBSERVATIONS HAVE LED US TO DOWNGRADE TO A HIGH SURF 
ADVISORY FOR MOST NORTH AND WEST FACING SHORES OF THE SMALLER 
ISLANDS. THE ADVISORY SHOULD BE DROPPED BY EVENING. MORE ADVISORY 
LEVEL SURF IS POSSIBLE THIS WEEKEND.

A SMALL CRAFT ADVISORY /SCA/ ALSO REMAINS IN EFFECT FOR EXPOSED 
COASTAL WATERS DUE TO COMBINED SEAS...MAINLY FROM THE LARGE NW 
SWELL. THE SCA WILL BE DOWN BY EVENING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST TODAY FOR THE NORTH AND WEST 
FACING SHORES OF NIIHAU KAUAI OAHU AND MOLOKAI...AND NORTH FACING 
SHORES OF MAUI.

SMALL CRAFT ADVISORY UNTIL 6 PM HST TODAY FOR ALL HAWAIIAN WATERS 
EXCEPT LEEWARD WATERS OF MAUI INCLUDING MAALAEA BAY AND WATERS SOUTH 
OF THE BIG ISLAND.

&&

$$

PUBLIC AND MARINE...WROE
AVIATION...DEJESUS