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Hawaiian Islands Synoptic Discussion and Guidance

829
FXHW60 PHFO 310643
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
843 PM HST THU OCT 30 2014

.SYNOPSIS...
MOISTURE FROM A DISSIPATING FRONT WILL PRODUCE FREQUENT SHOWERS
TONIGHT AND FRIDAY...ESPECIALLY ACROSS WINDWARD AREAS. BREEZY
TRADE WINDS WILL CONTINUE THROUGH FRIDAY NIGHT BEFORE DROPPING A
NOTCH OVER THE WEEKEND. WINDWARD SHOWERS WILL CONTINUE THROUGH THE
WEEKEND WHILE A DECREASE IN LEEWARD SHOWERS IS EXPECTED.

&&

.DISCUSSION...
FAST MOVING SHOWERS CONTINUE TO AFFECT MAINLY WINDWARD SECTIONS OF
THE STATE THIS EVENING. THESE SHOWERS HAVE REMAINED MOSTLY LOW
TOPPED AND LIGHT TO MODERATE...WHICH COMBINED WITH THE RAPID
MOTION HAS PREVENTED ANY EXCESSIVE RAINFALL AMOUNTS. SURFACE
ANALYSIS DEPICTS A DISSIPATING FRONT ACROSS THE WESTERN END OF
THE STATE...WITH A 1032 MB HIGH CENTERED ABOUT 1100 MILES NORTH
OF HONOLULU. FRESH TO STRONG TRADES PREVAIL OVER THE REGION TO
THE SOUTH OF THIS HIGH. WATER VAPOR IMAGERY INDICATES AN UPPER
LEVEL TROUGH IN THE PROCESS OF CUTTING OFF INTO A CLOSED LOW OVER
THE AREA...WHILE MIMIC-TPW IMAGERY SHOWS A NARROW RIBBON OF
ENHANCED MOISTURE ALONG THE DISSIPATING FRONT LYING ACROSS KAUAI
AND OAHU. THE 00Z LIHUE SOUNDING FOUND NO SIGNIFICANT INVERSION
AND SOMEWHAT ABOVE NORMAL PWAT OF 1.64 INCHES...WHILE THE 00Z HILO
SOUNDING FOUND MORE TYPICAL CONDITIONS WITH AN INVERSION BASED
NEAR 8000 FEET AND A NEAR NORMAL PWAT OF 1.32 INCHES.

OVERNIGHT INTO FRIDAY...WOULD EXPECT FREQUENT SHOWERS TO CONTINUE
ACROSS WINDWARD AREAS...WITH SOME OF THE SHOWERS SPILLING OVER
INTO LEEWARD SECTIONS OF THE SMALLER ISLANDS DUE TO THE BRISK
TRADE WIND FLOW. THE PRESENCE OF ENHANCED MOISTURE AND INSTABILITY
ALOFT COULD ALLOW FOR GREATER VERTICAL DEVELOPMENT OF SOME OF THE
SHOWERS...BUT THE CONTINUED FAST SHOWER MOTION WILL MAKE EXCESSIVE
RAINFALL AMOUNTS UNLIKELY UNLESS A TRAINING SITUATION IS ABLE TO
DEVELOP. MODELS INDICATE A LOW BUT NON-ZERO POTENTIAL FOR
THUNDERSTORMS TO DEVELOP UNDERNEATH THE UPPER TROUGH TO THE EAST
AND NORTHEAST OF MAUI...BUT GIVEN THAT NO STORMS HAVE BEEN
OBSERVED IN THE REGION DURING THE PAST SEVERAL HOURS WILL NOT
INCLUDE SUCH IN THE FORECAST AT THIS TIME. NO FORECAST UPDATES ARE
PLANNED FOR THIS EVENING.

TRADES WILL GRADUALLY WEAKEN DURING THE WEEKEND AS THE SURFACE HIGH
SHIFTS NORTHEAST OF THE STATE AND ANOTHER COLD FRONT MOVES EASTWARD
NORTH OF 30N. LINGERING MOISTURE FROM THE NEARBY DISSIPATED FRONT
AND THE PROXIMITY OF A MID/UPPER LEVEL TROUGH SHOULD KEEP SHOWERS
ACTIVE ACROSS WINDWARD AREAS...ESPECIALLY AT NIGHT...WITH
SCATTERED SHOWERS CONTINUING TO SPILL INTO SOME LEEWARD AREAS.

DURING THE FIRST HALF OF NEXT WEEK...ANOTHER STRONG SURFACE HIGH
PUSHING EASTWARD ACROSS THE DATELINE WILL FORCE THE FRONTAL
BOUNDARY SLOWLY SOUTHEASTWARD TOWARD THE STATE. LOW LEVEL WINDS
WILL VEER SLIGHTLY TO THE EAST-SOUTHEAST IN RESPONSE...WITH
SOME DEGREE OF ENHANCED MOISTURE POSSIBLY BEING DRAWN UP FROM THE
DEEP TROPICS OVER OUR AREA. MODEL CONSENSUS THEN DISSIPATES THE
FRONT NEAR OR JUST NORTH OF THE STATE BY NEXT THURSDAY...AS THE
SURFACE HIGH MOVES WELL NORTH OF THE AREA. TRADES SHOULD INCREASE
A NOTCH ONCE AGAIN...WITH A TYPICAL WINDWARD SHOWER PATTERN
CONTINUING.

&&

.AVIATION...
MODERATE TO LOCALLY STRONG TRADES CONTINUE ACROSS THE ISLANDS THIS
EVENING AND WILL PREVAIL THROUGH FRIDAY. THEREFORE THE AIRMET FOR
LOW LEVEL TURB WILL PERSIST. LOW CLOUDS FROM A DISSIPATING COLD
FRONT HAVE REACHED KAUAI AT THIS TIME AND WILL SPREAD TO THE REST OF
THE SMALLER ISLANDS THROUGH THE REST OF THE EVENING INTO EARLY
FRIDAY MORNING. EXPECT AN INCREASE IN SHRA AND MVFR CEILING
CONDITIONS FOR THE SMALLER ISLANDS AS THE NIGHT PROGRESSES. THERE
MAY EVEN BE ENOUGH LOW CLOUDS TO WARRANT AN AIRMET FOR MOUNTAIN
OBSCURATION FOR THE SMALLER ISLANDS. MOISTURE AT THE MID AND UPPER
LEVELS ASSOCIATED WITH A TROUGH HAS SPREAD OVER THE SOUTHERN ISLANDS
AND BROUGHT LIGHT ICING TO THOSE AREA...AS REPORTED BY AN AIRCRAFT
EARLIER. EXPECT THE MOISTURE TO DISSIPATE OVERNIGHT AND THUS THE
CONDITION WILL END.

&&

.MARINE...
A COMBINATION OF NORTH SWELL AND TRADE DRIVEN WIND WAVES CONTINUES
TO PRODUCE ELEVATED SURF ON NORTH AND EAST FACING SHORES. ANOTHER
REINFORCING NORTH SWELL WILL ARRIVE LATE TONIGHT AND FRIDAY...THEN
SLOWLY DIMINISH THROUGH THE WEEKEND. A HIGH SURF ADVISORY REMAINS
IN EFFECT THROUGH FRIDAY NIGHT FOR EAST FACING SHORES. SURF ALONG
SOUTH FACING SHORES WILL REMAIN SMALL THROUGH MONDAY...WITH A
SLIGHT BUMP TUESDAY AS A NEW LONG PERIOD SWELL ARRIVES. ANOTHER
SMALL NORTHWEST SWELL WILL ARRIVE TUESDAY AS WELL.

A SMALL CRAFT ADVISORY /SCA/ REMAINS POSTED THROUGH FRIDAY NIGHT
FOR MOST COASTAL AREAS DUE TO STRONG WINDS AND HIGH SEAS. WINDS
AND SEAS SHOULD SUBSIDE SOMEWHAT BY SATURDAY...BUT SCA WINDS WILL
PROBABLY CONTINUE ACROSS THE TYPICALLY WINDY AREAS AROUND MAUI
COUNTY AND THE BIG ISLAND.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST SATURDAY FOR EAST FACING SHORES
OF KAUAI OAHU MOLOKAI MAUI AND BIG ISLAND.

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

&&

$$

DISCUSSION/MARINE...JACOBSON
AVIATION...HUI




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