Flash Flood Warning 11, NWS Honolulu, HI

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST WED FEB 2 2005

.SYNOPSIS...
A TROUGH WILL CONTINUE TO CREATE VERY UNSTABLE CONDITIONS OVER THE
ISLANDS TODAY. THIS INSTABILITY WILL PROMOTE THE DEVELOPMENT OF
HEAVY SHOWERS AND THUNDERSTORMS. THE TROUGH WILL GRADUALLY WEAKEN
STARTING TONIGHT...ALLOWING DRIER WEATHER TO RETURN. THE TROUGH IS
ALSO KEEPING WINDS LIGHT OVER THE ISLANDS. AS THE TROUGH WEAKENS...
TRADE WINDS WILL RETURN BY THIS WEEKEND.

&&

.DISCUSSION...
A NORTHEAST TO SOUTHWEST TROUGH...AT THE SURFACE AND ALOFT...IS
CENTERED OVER THE MAIN HAWAIIAN ISLANDS. WITH THE TROUGH OVER THE
ISLANDS...THE ATMOSPHERE CONTINUES TO BE VERY UNSTABLE AND
THUNDERSTORMS CONTINUE TO FORM AROUND THE ISLANDS. SATELLITE IMAGERY
AND SURFACE ANALYSES SHOW A SURFACE LOW WITHIN THE TROUGH SOUTHWEST
OF THE ISLANDS. WITH THE TROUGH OVER THE ISLANDS...LOW LEVEL WINDS
ARE GENERALLY NORTHEAST NEAR KAUAI AND SOUTHEAST NEAR THE BIG ISLAND
OF HAWAII.

BROKEN LAYERED CLOUDS COMPLETELY BLANKET THE MAIN HAWAIIAN ISLANDS
BLOCKING THE VIEW OVER LOWER LEVEL FEATURES BUT FROM WHAT WE CAN
TELL FROM RADAR IMAGERY THERE ARE EMBEDDED THUNDERSTORMS...MOSTLY
NORTHWEST OF MOLOKAI. THE NORTHEAST FLOW NEAR THE SURFACE IS
KEEPING THUNDERSTORMS ANCHORED OVER KAUAI SO HEAVY RAIN CONTINUES
THERE. THUNDERSTORMS ARE ALSO CONCENTRATED OVER WATER SOUTHWEST OF
OAHU...POSSIBLY ALONG A CLOUD PLUME IN THE LEE OF THE ISLAND.

THE COMPUTER MODELS ALL SHOW A TROUGH REMAINING OVER THE ISLANDS
AND GRADUALLY WEAKENING...BUT AS HAS GENERALLY BEEN THE CASE WITH
THIS WEATHER SYSTEM...THE MODELS DIFFER ON THE DETAILS. THE GFS
SHOWS THE CLOUDS AND SHOWERS DISSIPATING RAPIDLY TONIGHT...WHILE
THE NAM AND NOGAPS SHOW A SLOWER DISSIPATION. THE GFS HAS NOT
PERFORMED AS WELL AS SOME OF THE OTHER MODELS...SO WE WILL FOLLOW
THE ETA AND KEEP THUNDERSTORMS...HEAVY SHOWERS AND EXTENSIVE CLOUDS
THROUGH TOMORROW.

WHILE DIFFERING IN THE DETAILS...THE MODELS ARE IN GENERAL
AGREEMENT ON A SURFACE LOW MOVING NORTHEAST OVER THE ISLANDS THIS
EVENING WITH THE LOW MOVING AWAY TO THE NORTHEAST TOMORROW. WHEN
THE LOW MOVES NORTH OF THE ISLANDS THIS EVENING...THE GREATEST
CHANCE FOR HEAVY RAIN WILL SHIFT SOUTHEAST AWAY FROM KAUAI AND OAHU
AND OVER MAUI COUNTY AND THE BIG ISLAND TONIGHT AND TOMORROW. IT
WILL PROBABLY BE NECESSARY TO EXTEND THE FLASH FLOOD WATCH FOR
KAUAI AND OAHU THROUGH TONIGHT AND THE WINTER WEATHER ADVISORY FOR
THE BIG ISLAND SUMMITS AND THE FLASH FLOOD WATCH FOR MAUI COUNTY AND
THE BIG ISLAND THROUGH TOMORROW.

THE CLOUD BAND OVER THE ISLANDS WILL CONTINUE TO SLOWLY WEAKEN AND
SLOWLY SHIFT SOUTHEAST FRIDAY. BY FRIDAY NIGHT THE CLOUD BAND
ASSOCIATED WITH THE TROUGH WILL BE EAST OF THE BIG ISLAND AND TRADE
WIND WEATHER WILL BE RETURNING TO THE ISLANDS.

THIS IS A LARGE AND COMPLEX SYSTEM...AND THE MODELS HAVE NOT BEEN
PERFORMING TOO WELL...SO THE SCENARIO I HAVE OUTLINED ABOVE MAY WELL
REQUIRE ADJUSTMENTS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FOR NIIHAU KAUAI OAHU THROUGH TONIGHT.

FLASH FLOOD WATCH FOR MAUI MOLOKAI LAND KAHOOLAWE AND THE BIG ISLAND
THROUGH TOMORROW.

WINTER WEATHER ADVISORY FOR BIG ISLAND SUMMITS THROUGH TOMORROW.

&&

DONALDSON

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
908 AM HST WED FEB 02 2005

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0302 AM     FLASH FLOOD      HANALEI                 22.21N 159.50W
02/02/2005                   KAUAI              HI   LAW ENFORCEMENT

            HANALEI BRIDGE CLOSED AT 210AM.

0845 AM     WATER SPOUT      4 NNW MAILI             21.47N 158.21W
02/02/2005                   HONOLULU           HI   TRAINED SPOTTER

            LARGE WATERSPOUT REPORTED 2 MILES OFFSHORE MAKAHA.

0845 AM     WATER SPOUT      6 W BARBERS POINT HOUSI 21.32N 158.18W
02/02/2005                   XXX                XX   NWS EMPLOYEE

            WATERSPOUT SPOTTED OFF THE COAST OF BARBERS POINT.

&&

LHARLAN