Flash Flood Warning 110, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST WED MAR 29 2006

.SYNOPSIS...
LOCALLY HEAVY SHOWERS AND POSSIBLE THUNDERSTORMS WILL IMPACT THE
MAIN HAWAIIAN ISLANDS THROUGH FRIDAY. A LOW ALOFT WILL LINGER NEAR
THE MAIN HAWAIIAN ISLANDS THROUGH THE WEEKEND...MAINTAINING THE
PREDOMINANTLY CLOUDY AND WET WEATHER.

&&

.DISCUSSION...
THE PATTERN IS BEGINNING TO HEAT UP AROUND THE HAWAIIAN ISLANDS AND
CONDITIONS WILL DETERIORATE OVERNIGHT. A SURFACE TROUGH NORTH
THROUGH WEST OF THE ISLANDS...ROUGHLY 175 MILES WEST OF KAUAI AT ITS
CLOSEST POINT...REMAINS NEARLY STATIONARY. THE 2 PM SURFACE ANALYSIS
SHOWS A WEAK SURFACE LOW HAS FORMED WITHIN THE TROUGH NEAR 25N
161W...OR 200 MILES NORTHWEST OF KAUAI. THE LOW AND TROUGH CONTINUE
TO CAUSE LOW LEVEL WINDS TO CONVERGE OVER THE STATE. THE LOW LEVEL
CONVERGENCE AND THE AMPLE MOISTURE ALREADY IN PLACE WILL PRODUCE
SHOWERS ACROSS THE STATE TONIGHT.

WATER VAPOR LOOPS SHOW THAT THE TROUGH ALOFT TO THE WEST OF THE
ISLANDS HAS DEEPENED SUFFICIENTLY ENOUGH TO TAP INTO A HEALTHY
TROPICAL MOISTURE SOURCE. THE PIPES ARE NOW OPEN...AS A STRONG...150
MPH JET STREAM ON THE SOUTHEASTERN SIDE OF THE TROUGH IS
TRANSPORTING A DEEP LAYER OF MID TO UPPER LEVEL MOISTURE UP AND OVER
THE ISLANDS. THE AFTERNOON SOUNDING OVER LIHUE SHOWS THE ATMOSPHERE
HAS COOLED 2 TO 4 DEGREES CELSIUS OVER THE PAST 24 HOURS FROM 800
MB...OR 6500 FEET ON UP. LAPSE RATES ALOFT HAVE BECOME MORE UNSTABLE
AS WELL. THE OVERALL INCREASE IN INSTABILITY CAN ALSO BE INFERRED
THROUGH THE APPEARANCE OF ISOLATED HEAVY SHOWERS AND THUNDERSTORMS
ACROSS THE STATE THIS AFTERNOON. THE LOW ALOFT WE ARE
WATCHING...CURRENTLY LOCATED NEAR 27N 164W...OR 450 MILES NORTHWEST
OF KAUAI...IS SLOWLY SLIDING SOUTHWARD AND CLOSER TO THE ISLANDS.
THE LOW ALOFT WILL SETTLE IN JUST NORTHWEST OF KAUAI BY THURSDAY
MORNING...PLACING THE ISLANDS UNDER A FAVORABLE REGION FOR HEAVY
SHOWERS AND POSSIBLE THUNDERSTORMS. THIS FEATURE HAS BEEN HANDLED
WELL BY THE VARIOUS GLOBAL MODELS...AND WILL BE THE MAIN SOURCE OF
UPPER LEVEL SUPPORT OVER THE COMING DAYS AS IT LINGERS NEAR THE
ISLANDS.

RECENT MODEL RUNS ARE IN BETTER AGREEMENT OVERALL WITH THE MOVEMENT
OF THE LOW ALOFT FROM THURSDAY ON...BUT TO THE DETRIMENT OF ISLAND
WEATHER. THE MODEL CONSENSUS NOW KEEPS THE LOW ALOFT JUST NORTHWEST
OR WEST OF THE STATE THROUGH THE WEEKEND MAINTAINING THE THREAT OF
HEAVY SHOWERS AND POSSIBLE THUNDERSTORMS. FOR NOW WILL EXTEND THE
FLASH FLOOD WATCH THROUGH FRIDAY AFTERNOON.

THE QUESTION REMAINS WHEN WILL IT ALL END. MODELS KEEP A SURFACE
TROUGH OVER OR JUST WEST OF THE ISLANDS INTO THE START OF NEXT
WEEK...SO THE QUESTION WILL REMAIN UNANSWERED. WITH THE TROUGH WEST
OF THE STATE...WINDS WILL SWING AROUNG TO THE EAST
SOUTHEAST...WHICH WILL FOCUS RAINFALL ALONG WINDWARD SECTIONS ONCE
AGAIN...TAKING US BACK TO WHERE WE STARTED.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

FLASH FLOOD WATCH FOR ALL ISLANDS UNTIL 6 PM FRIDAY.

&&

TANABE