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Hawaiian Islands Synoptic Discussion and Guidance

013
FXHW60 PHFO 030758 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1000 PM HST MON MAR 2 2015

.UPDATE...
I HAVE UPDATED THE FORECASTS TO INCREASE CLOUDS AND SHOWERS OVER
KAUAI THIS EVENING AND DECREASE CLOUDS AND SHOWERS A BIT OVER OAHU
AND MAUI COUNTY. ALSO...AIRMET SIERRA HAS BEEN UPDATED TO ADD MTN
OBSC FOR KAUAI AND DROP MTN OBSC FOR THE BIG ISLAND.

&&

.SYNOPSIS...
HIGH PRESSURE NORTHWEST OF THE AREA WILL KEEP TRADE WINDS BLOWING
OVER THE ISLANDS. A TROUGH ALOFT WILL KEEP THE WEATHER RATHER WET...
ESPECIALLY ON THE BIG ISLAND OF HAWAII...THROUGH WEDNESDAY NIGHT.

&&

.DISCUSSION...
THE HEAVY SHOWERS THAT DEVELOPED OVER THE BIG ISLAND AND MAUI
EARLIER TODAY HAVE MOSTLY DISSIPATED...BUT AS OF 800 PM SOME SHOWERS
PERSISTED OVER THE SOUTHEAST SLOPES OF THE BIG ISLAND. HIGH PRESSURE
TO THE NORTHWEST IS PRODUCING GENTLE TO FRESH TRADE WINDS ACROSS THE
ISLANDS. THE TRADES ARE PUSHING ISOLATED LIGHT SHOWERS OVER WINDWARD
AREAS OF THE SMALLER ISLANDS...BUT MOST AREAS OF THE SMALLER ISLANDS
WILL BE DRY OVERNIGHT. THE WEATHER OVER THE BIG ISLAND WILL BE LESS
ACTIVE TOMORROW WHILE MOSTLY DRY TRADE-WIND WEATHER WILL CONTINUE
OVER THE SMALLER ISLANDS.

A DEEP TROUGH ALOFT WILL PERSIST NORTH OF THE AREA FOR AT LEAST THE
NEXT WEEK. A SHORT-WAVE TROUGH WITHIN THE LARGER TROUGH WILL
APPROACH THE ISLANDS FROM THE NORTHWEST STARTING TUESDAY AFTERNOON.
AS THE TROUGH APPROACHES...THE ATMOSPHERE WILL BECOME MORE UNSTABLE
AND MOISTURE WILL SPREAD OVER THE ISLANDS FROM THE SOUTHEAST.
ANOTHER ROUND OF HEAVY SHOWERS OR THUNDERSHOWERS IS POSSIBLE WITH
GREATEST THREAT ON WEDNESDAY NIGHT ON THE BIG ISLAND. THE TROUGH
ALOFT WILL ALSO LIKELY PRODUCE STRONG WINDS AND SNOW OVER THE HIGH
ELEVATIONS ON THE BIG ISLAND.

CLOUDS AND SHOWERS WILL SUBSIDE AGAIN STARTING THURSDAY AS THE
SHORT-WAVE MOVES OFF TO THE NORTHEAST. MEANWHILE...A STRONG SURFACE
HIGH WILL BUILD NORTHWEST OF THE AREA. STRENGTHENING TRADE WINDS
WILL BRING DRIER AIR BACK OVER THE ISLANDS THROUGH THE END OF THE
WEEK. THE TRADE WINDS MAY BE QUITE BREEZY THROUGH THE WEEKEND.

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL OVERNIGHT BUT A LINE OF SHOWERS WILL
PRODUCE MVFR CONDITIONS ON KAUAI. AIRMET SIERRA HAS BEEN UPDATED TO
DROP THE MTN OBSC ON THE BIG ISLAND AND ADD MTN OBSC ON KAUAI.

MID TO UPPER LEVEL TURBULENCE REMAINS OVER THE BIG ISLAND AND MAUI
DUE TO THE TROUGH ALOFT OVER THESE ISLANDS. AIRMET TANGO IS NOW IN
EFFECT FOR MODERATE TURBULENCE...BUT WE EXPECT TO DROP THE AIRMET
LATER TONIGHT.

&&

.MARINE...
A TROUGH CONTINUES TO PRODUCE ISOLATED THUNDERSTORMS OVER THE WATERS
EAST THROUGH SOUTH OF THE BIG ISLAND. THE THUNDERSTORMS WILL LIKELY
DIMINISH ON TUESDAY BUT MAY BECOME MORE ACTIVE AGAIN WEDNESDAY NIGHT.

THE NORTHWEST SWELL THAT PROMPTED THE HIGH SURF ADVISORY ON SUNDAY
HAS DIMINISHED RAPIDLY...SO THE ADVISORY HAS BEEN CANCELLED.
COMBINED SEAS HAVE ALSO DROPPED...SO THE SMALL CRAFT ADVISORY WILL
ALSO BE CANCELLED.

TRADE WINDS WILL STRENGTHEN LATER IN THE WEEK AS A STRONG HIGH
BUILDS NORTHWEST OF THE AREA. THIS WILL LIKELY REQUIRE A SMALL
CRAFT ADVISORY FOR STRONG TRADE WINDS AND ROUGH SEAS. THE TRADE
WINDS WILL PRODUCE ROUGH SURF ALONG EAST FACING SHORES. THIS SURF
COULD REQUIRE A HIGH SURF ADVISORY LATER IN THE WEEK. OTHERWISE SURF
IS EXPECTED TO REMAIN BELOW THE ADVISORY THRESHOLDS.

&&

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

&&

$$
DONALDSON







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