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Hawaiian Islands Synoptic Discussion and Guidance

474
FXHW60 PHFO 301458
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
458 AM HST TUE SEP 30 2014

.SYNOPSIS...
LIGHT WINDS ACROSS THE STATE COMBINED WITH AN UNSTABLE AIRMASS WILL
RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THIS EVENING.
A MORE STABLE AIRMASS IS EXPECTED FOR THE SECOND HALF OF THE
WEEK... BUT LIGHT WINDS AND MUGGY CONDITIONS WILL REMAIN.

&&

.DISCUSSION...

HIGH PRESSURE FAR TO THE NORTHEAST IS BEING PUSHED AWAY FROM THE
STATE BY AN APPROACHING COLD FRONT NORTHWEST OF THE ISLANDS. THIS
SCENARIO LEAVES HAWAIIAN UNDER LIGHT EAST- SOUTHEAST FLOW BETWEEN
THE TWO FEATURES. AFTERNOON SEA BREEZES AND NIGHTTIME LAND BREEZE
CIRCULATIONS WILL CONTINUE THROUGH THE NEXT SEVERAL OF DAYS. DEW
POINTS WILL REMAIN IN THE LOW 70/S AND SENSIBLE WEATHER CONDITIONS
WILL REMAIN MUGGY AND HOT THROUGH THE WEEK.

ALOFT...WE HAVE A WEAK UPPER LOW THAT HAS DESTABILIZED OUR
ATMOSPHERE ALLOWING FOR ISOLATED THUNDERSTORMS TO FORM OVER THE
STATE AND COASTAL WATERS. WITHOUT A SIGNIFICANT STEERING FLOW NEAR
THE SURFACE... SHOWERS AND THUNDERSTORMS WILL FORM IN PLACE AND TEND
TO REMAIN STATIONARY OR SLOWLY DRIFT... BEFORE RAINING ITSELF OUT. A
HANDFUL OF FLOOD ADVISORIES HAVE BEEN ISSUED FOR THESE GULLY WASHERS
THAT HAVE LASTED LONG ENOUGH TO CREATE NUISANCE FLOODING. A FLASH
FLOOD WARNING IS NOT OUT OF THE QUESTION... BUT THAT WOULD BE A
WORST CASE SCENARIO.

SKIES WILL BE PARTLY CLOUDY THIS MORNING BUT WILL QUICKLY BECOME
MOSTLY CLOUDY BY LATE MORNING AS LAND HEATING AND SEA BREEZES
PROVIDE LIFT OVER THE ISLANDS. A CHANCE OF THUNDERSTORMS AND HEAVY
SHOWERS REMAINS THROUGH THIS EVENING AS THE UPPER LOW SLOWLY
WEAKENS AND DRIFTS NORTHEAST. THE BEST CHANCE FOR SHOWERS AND
THUNDERSTORMS OVER LAND WILL BE THIS AFTERNOON... DURING PEAK
HEATING. GUIDANCE INDICATES SLOW WARMING ALOFT AS THE LOW MOVES
AWAY SO EXPECT THUNDERSTORMS TO DWINDLE INTO THE EVENING HOURS.
MOISTURE REMAINS ABUNDANT IN THE LOW LEVELS AND ANY FORCING DUE TO
THE UPPER LOW OR CONVERGENCE AROUND THE ISLANDS TODAY WILL SET
OFF HEAVY SHOWERS.

AS THE UPPER TROUGH WEAKENS AND DRIFTS NORTH...INSTABILITY AROUND
THE ISLANDS WILL DECREASE. WEAK EASTERLY TRADES WILL REMAIN FOR
THE LAST HALF OF THE WEEK AS ANOTHER FRONT TO THE NORTHWEST KEEPS
HIGH PRESSURE AT BAY TO THE NORTHEAST. LOCAL SEA BREEZES WITH
AFTERNOON CLOUDS AND SHOWERS WILL CONTINUE... AND NIGHT TIME LAND
BREEZES WILL PARTIALLY CLEAR SKIES.

&&

.AVIATION...
VFR WILL BE THE PRIMARY FLYING CONDITION AREA WIDE. A MOIST AND
UNSTABLE AIR MASS OVER THE FA IS RESPONSIBLE FOR THE WIDELY DISPERSED
HEAVY SHOWERS AND ISOLATED THUNDERSTORMS THIS MORNING... MOSTLY
OVER WATERS.

AS THE MORNING PROGRESSES...THESE SHOWERS AND THUNDERSTORMS WILL
DIMINISH OVER WATER AND INCREASE OVER LAND IN THE AFTERNOON. EXPECT
MVFR TO ISOL IFR CONDITIONS WITH THESE SHOWERS AND STORMS.

A MORE STABLE AIR MASS IS EXPECTED TO SPREAD ACROSS THE AREA AFT
010400 UTC WITH THE THREAT OF HEAVY SHOWERS AND THUNDERSTORMS ENDING.

NO AIRMETS CURRENTLY IN EFFECT.


&&

.MARINE...
SCATTERED THUNDERSTORMS AND HEAVY SHOWERS ARE POSSIBLE TODAY OVER
THE COASTAL WATERS. OTHERWISE... LIGHT EAST TO SOUTHEAST WINDS
WILL CONTINUE THROUGH THE WEEK. ONLY SMALL SWELLS ARE ANTICIPATED
TO MOVE THROUGH THE AREA THIS WEEK. A SMALL NORTHWEST SWELL IS
EXPECTED TO ARRIVE TODAY...AND PEAKING WEDNESDAY. THIS SWELL WILL
BE REINFORCED BY A SMALL NORTHWEST FRIDAY. THE SOUTH FACING SHORES
WILL ENCOUNTER A SERIES OF SMALL SWELLS FROM THE SOUTH THROUGH
THURSDAY...THE LARGEST ARRIVING ON TUESDAY THROUGH THURSDAY.

&&

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

&&

$$

MORRISON...DISCUSSION AND MARINE
LAU...AVIATION




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