Severe Thunderstorm Warning 9, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST THU MAR 30 2006

.SYNOPSIS...
AN UPPER LOW TO THE WEST OF THE STATE WILL CONTINUE TO GIVE THE
ISLANDS A RISK OF FLOODING RAINS THROUGH ABOUT FRIDAY. ALTHOUGH DEEP
TROPICAL MOISTURE WILL DIMINISH THIS WEEKEND...THE AIRMASS WILL
REMAIN UNSTABLE ENOUGH FOR ISOLATED THUNDERSTORMS THROUGH SATURDAY.
EARLY NEXT WEEK...DRIER AIR AND TRADE WINDS ARE EXPECTED TO MAKE A
LONG AWAITED RETURN.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A SOUTHWESTERLY CONVEYOR BELT OF DEEP
LAYER MOISTURE CONTINUING TO STREAM NORTHEAST ACROSS THE STATE. AN
UPPER LEVEL LOW IS NEAR 25N 163W...AND A NUMBER OF SHORTWAVES ARE
ROTATING AROUND IT...ENHANCING POCKETS OF DEEP CONVECTION FROM TIME
TO TIME OVER THE ISLANDS. ONE SHORTWAVE IS NEAR NIIHAU...AND ANOTHER
IS NEAR 21N 167W. WHILE THE OVERALL SYNOPTIC FLOW OVER THE ISLANDS
AT THE SURFACE IS SOUTHEASTERLY...THE THUNDERSTORM COMPLEX HAS BEEN
DISRUPTING THE FLOW AND WINDS BEHIND THE LEADING EDGE HAVE
TEMPORARILY TURNED NORTHWESTERLY.

AS THE UPPER LOW SLIDES SOUTHEAST TOWARD THE ISLANDS...WE WILL SEE
A FEW MORE WAVES OF RAIN AND THUNDERSTORMS SPREADING OVER THE
ISLANDS TONIGHT THROUGH FRIDAY NIGHT. WE WILL NEED TO KEEP THE FLASH
FLOOD WATCH GOING SINCE WE WILL CONTINUE TO HAVE ALL THE INGREDIENTS
IN PLACE. TIMING AND PLACEMENT OF THESE WAVES WILL BE DIFFICULT AT
BEST...AND SO THE GRIDS HAVE A RATHER WET BROAD BRUSH THROUGH THAT
TIME FRAME.

IT STILL LOOKS AS THOUGH WE SHOULD SEE GRADUAL IMPROVEMENT THIS
WEEKEND...AS THE PLAYERS WHICH HAVE BEEN KEEPING IT WET FINALLY
BEGIN TO GO THEIR SEPERATE WAYS. HOWEVER...WE CANNOT LET OUR GUARD
DOWN EVEN INTO SATURDAY. AS THE UPPER LOW PUSHES OVER THE ISLANDS...
THE AIRMASS WILL GET MORE UNSTABLE AND SO WHILE RAINFALL WILL BE
LESS WIDESPREAD...THE STORMS THEMSELVES MAY BE RATHER INTENSE WITH
VERY LOCALIZED GUSTY WINDS AND HAIL. HAVE ADDED THUNDERSTORMS TO THE
GRIDS FOR SATURDAY. ANOTHER CONCERN FOR FRIDAY INTO SATURDAY IS
THAT THE SOUTHEAST FLOW WOULD AIM ANY LEE-SIDE CONVERGENCE PLUMES AT
KAUAI AND OAHU.

LOW LEVEL TROUGHING SHOULD SHIFT WEST OF THE ISLANDS BY SUNDAY...
WHILE THE UPPER LEVEL TROUGH SHOULD PUSH EAST OF US BY MONDAY. WE
ARE DISCOUNTING THE GFS PERSISTENT IDEA OF DEVELOPING ANOTHER
SURFACE LOW NEAR THE ISLANDS AS CONVECTIVE FEEDBACK...AND HAVE
TRENDED WITH THE OTHER MODELS IN TURNING THE SOUTHEASTERLY WINDS
BACK TO EASTERLY TRADES BY SUNDAY. WITH THE UPPER TROUGH NEARBY TO
THE EAST...INITIALLY THE TRADES WILL BE RATHER WET. THE MODELS
ACTUALLY SHOW MUCH DRIER AIR WITH BELOW NORMAL 850 MB THETA-E
PUSHING IN FROM THE EAST EARLY NEXT WEEK THAT WOULD BE A WELCOME
RELIEF FROM THE DRENCHING WE/VE SEEN THE PAST SIX WEEKS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR ALL HAWAIIAN ISLANDS.

WINTER WEATHER ADVISORY UNTIL 7 PM HST FRIDAY FOR BIG ISLAND SUMMITS.

&&

R BALLARD