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Hawaiian Islands Synoptic Discussion and Guidance
968
FXHW60 PHFO 211411
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST TUE MAY 21 2013
.SYNOPSIS...
A LAND AND SEA BREEZE WEATHER PATTERN WILL PERSIST OVER THE ISLANDS
THROUGH WEDNESDAY AS AN AREA OF LOW PRESSURE STAYS SEVERAL HUNDRED
MILES NORTH OF THE STATE. LINGERING MOISTURE ASSOCIATED WITH THE LOW
PRESSURE WILL BRING SLIGHTLY HIGHER CHANCES OF RAIN TO THE EASTERN
PORTION OF THE STATE TODAY. TRADE WINDS WILL REBUILD OVER THE
ISLANDS BY THURSDAY AS THE AREA OF LOW PRESSURE DRIFTS AWAY AND
DISSIPATES WHILE A SURFACE HIGH PRESSURE MOVES TO FAR NORTHEAST OF
THE STATE.
&&
.DISCUSSION...
AN AREA OF SURFACE LOW PRESSURE PERSISTS IN THE ISLAND VICINITY
THIS MORNING...KEEP WINDS LIGHT OVER THE ISLANDS. LAND BREEZES HAVE
DEVELOPED OVERNIGHT RESULTING IN A DECREASE IN SHOWERS OVER THE
ISLANDS. MOISTURE FROM A DISSIPATING FRONT AS WELL AS LOW LEVEL
CONVERGENCE BANDS LINGERS OVER THE EASTERN PORTION OF THE MAIN
HAWAIIAN ISLANDS. THE MOISTURE...COUPLED A SLIGHTLY UNSTABLE AIR
MASS...AS DEPICTED BY EARLY MORNING HILO SOUNDING...HAS ALLOWED SOME
DEEPER CONVECTION TO DEVELOP IN THE MAUI COUNTY AND BIG ISLAND
VICINITY SINCE LAST NIGHT. THERE IS ALSO A BATCH OF LOW CLOUDS
AFFECTING KAUAI...THOUGH EARLY MORNING LIHUE SOUNDING INDICATES THE
AIR MASS IS MORE STABLE AND DRIER COMPARED TO HILO/S. STRONG WINDS
ASSOCIATED WITH THE UPPER LEVEL LOW PRESSURE SYSTEM CONTINUE TO
AFFECT THE SUMMITS OF THE BIG ISLAND EARLY THIS MORNING. THE WINDS
WILL PROBABLY LAST THROUGH THIS EVENING...THEREFORE A WIND ADVISORY
REMAINS IN EFFECT FOR THAT AREA. EXPECT A REPEAT OF YESTERDAY
WEATHER OVER THE ISLANDS TODAY AS THE STATE/S WEATHER IS STILL
PRETTY MUCH UNDER THE INFLUENCE OF THE NEARBY LOW PRESSURE...WITH
HIGHEST THREAT OF RAIN AS WELL AS POSSIBLY LOCALLY HEAVY SHOWERS
OVER THE EASTERN ISLANDS. THE REST OF THE ISLANDS MAY SEE A CHANCE
OF RAIN...ESPECIALLY DURING THE AFTERNOON AND EVENING WITH THE
CONVECTIVE CLOUDS UNDER DAY TIME HEATING.
THE AREA OF SURFACE LOW PRESSURE WILL SLOWLY WEAKEN AND DRIFT AWAY
FROM THE ISLANDS IN THE NEXT COUPLE OF DAYS...AS THE ASSOCIATED
UPPER LEVEL CUT-OFF LOW LIFTS NORTH. WINDS WILL REMAIN LIGHT ENOUGH
OVER THE ISLANDS WEDNESDAY SUCH THAT THE PRESENT CONVECTIVE WEATHER
SCENARIO WILL CONTINUE. LINGERING MOISTURE ASSOCIATED WITH LOW LEVEL
CONVERGENCE AND THE OLD FRONTAL BOUNDARY IS ALSO EXPECTED TO HOVER
NEARLY THE EASTERN ISLANDS WHILE SLOWLY DISSIPATE. THEREFORE...A
SLIGHTLY HIGHER CHANCE OF RAIN IS EXPECTED OVER MAUI COUNTY AND THE
BIG ISLAND WEDNESDAY
FORECAST CHARTS INDICATE A SURFACE HIGH PRESSURE WILL MOVE TO
FAR NORTHEAST OF THE STATE BY THURSDAY. AS THE SURFACE LOW PRESSURE
SYSTEM DRIFTS AWAY AND DISSIPATES...TRADE WINDS WILL SLOWLY REBUILD
OVER THE ISLANDS. TRADE WIND WEATHER WILL RETURN TO THE STATE BY
THEN AS WELL. MOREOVER...THE SURFACE PRESSURE GRADIENT ACROSS THE
ISLANDS IS EXPECTED TO TIGHTEN BY THE WEEKEND. TRADE WINDS WILL
STRENGTHEN AND BECOME LOCALLY BREEZY. PASSING LOW CLOUDS AND SHOWERS
WILL AFFECT MAINLY WINDWARD AND MAUKA AREAS...AND MAY EVEN REACH THE
LEE AREAS OF THE SMALLER ISLANDS AT TIMES. FORECAST CHARTS DO HINT
THE DEVELOPMENT OF A WEAK UPPER FEATURE NEAR THE WESTERN ISLANDS.
THIS FEATURE MAY ENHANCE THE TRADE SHOWERS AT TIMES.
&&
.AVIATION...
VFR CONDITIONS CONTINUE FOR ALL TAF SITES THIS MORNING...WITH LOW
CLOUDS LINGERING IN THE ISLAND VICINITY. THERE ARE SOME DEEPER
CONVECTION PRESENT IN THE SURROUNDING COASTAL WATERS WITH TOPS TO AT
LEAST 10K FEET...BRINGING LOCALIZED MVFR CEILING AND SHRA. EXPECT
MOSTLY VFR CONDITIONS TO PREVAIL FOR ALL THE TAF SITES
TODAY...THROUGH WITH MOISTURE LINGERING OVER THE STATE...ESPECIALLY
OVER THE EASTERN ISLANDS...MORE BRIEF MVFR CEILING AND SHRA
CONDITIONS MAY DEVELOP DURING THE AFTERNOON AND EVENING OVER THE
ISLANDS.
&&
.MARINE...
THE HIGH SURF ADVISORY FOR SOUTH FACING SHORES CONTINUES THROUGH
THIS EVENING AS A LARGE SOUTH SWELL PERSISTS. ELEVATED SURF FOR
SOUTH FACING SHORES WILL LAST AT LEAST THROUGH WEDNESDAY. AN OUT OF
SEASON... MODERATE...WEST-NORTHWEST SWELL IS EXPECTED TO ARRIVE
TONIGHT AND PEAK WEDNESDAY INTO THURSDAY...BRINGING NEAR ADVISORY
LEVEL SURF FOR NORTH AND WEST FACING SHORES.
TRADE WINDS ARE EXPECTED TO BE STRONG ENOUGH BY THE WEEKEND FOR
SMALL CRAFT WIND CONDITIONS TO DEVELOP OVER THE WINDIER MAUI COUNTY
AND BIG ISLAND COASTAL WATERS.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 600 PM HST THIS EVENING FOR SOUTH SHORES OF
ALL ISLANDS.
WIND ADVISORY IN EFFECT FOR BIG ISLAND SUMMITS UNTIL 6 PM HST THIS
EVENING.
&&
$$
HUI
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
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It was last modified on: Tue, Sep 21 2010 - 2314 UTC
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