Flash Flood Watch 6, NWS Honolulu, HI

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST TUE NOV 27 2007

.SYNOPSIS...
OCCASIONAL HEAVY SHOWERS WILL PASS OVER SOUTHEAST SECTIONS OF THE
BIG ISLAND TODAY. THE REST OF THE STATE WILL SEE LESS RAIN. LIGHT
SOUTHEAST WINDS AND A CHANCE OF LOCALLY HEAVY RAIN WILL CONTINUE
THROUGH THE END OF THE WORK WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A WEAK RIDGE/COL OVER THE STATE...
STRETCHING BETWEEN HIGHS TO THE EAST NORTHEAST AND WEST SOUTHWEST.
AN UPPER LOW IS LOCATED SOUTH OF THE BIG ISLAND...WITH A SHARP
SHORTWAVE TROUGH TO THE NORTHWEST OF KAUAI. 12Z RAOBS FROM PHLI/PHTO
SHOW A MOIST AIRMASS BELOW 550MB...WITH LITTLE OR NO SUBSIDENCE
INVERSION. MODIFIED PHTO SOUNDING FOR A CONSERVATIVE 84/68 YIELDS A
CAPE OF 1100 J/KG. GIVEN THE LACK OF A CAP AND AVAILABLE
INSTABILITY...WILL ADD A MENTION OF THUNDER TO THE BIG ISLAND.
BETTER CHANCE LOOKS TO BE ACROSS KONA SLOPES...WHERE SKIES ARE
CURRENTLY SUNNY. HOWEVER GIVEN ANTECEDENT INSTABILITY WITH THE HEAVY
SHOWERS AND TCU OFFSHORE SOUTH OF THE BIG ISLAND...WILL INCLUDE A
MENTION OF THUNDER ALONG THE KAU COAST AS WELL.

BROAD SOUTHEASTERLY SURFACE FLOW WILL CONTINUE ACROSS THE STATE
THROUGH MUCH OF THE WORK WEEK...BETWEEN A HIGH FAR TO THE NORTHEAST
AND A STALLED FRONT TO THE NORTHWEST. THE FLOW OUT OF THE TROPICS
WILL CONTINUE TO BRING ABOVE NORMAL MOISTURE ACROSS THE STATE. 12Z
PHLI SOUNDING WAS DRIER THAN PHTO /PRECIPITABLE WATER OF 1.38 INCHES
AS OPPOSED TO 1.78 INCHES/...BUT 17Z-19Z AMSU/SSMI PASSES SHOW THE
TONGUE OF HIGHER PRECIPITABLE WATERS HAS REACHED KAUAI. SATELLITE
DERIVED PW/S ARE NEAR 1.9 INCHES. GIVEN THE AVAILABLE MOISTURE AND
LACK OF AN INVERSION...WILL MENTION THE POTENTIAL FOR HEAVY RAIN
ACROSS THE STATE. VISIBLE SATELLITE IMAGERY SHOWS CLOUD MOTIONS HAVE
ACTUALLY TAKEN ON MORE OF A SOUTHERLY COMPONENT WEST OF MAUI COUNTY.
THIS SHOULD KEEP ANY PLUME FROM MOLOKAI EAST OF OAHU. HOWEVER...AN
AREA OF CLOUDS AND SHOWERS THAT CAN BE TRACED BACK TO THE BIG ISLAND
PLUME IS CURRENTLY IMPINGING ON OAHU.

THE 500MB PATTERN DOES NOT CHANGE VERY MUCH OVER THE STATE THIS
WEEK. THE LOW SOUTHEAST OF THE BIG ISLAND WILL CONTINUE TO
WEAKEN...AND THE TROUGH TO THE NORTHWEST WILL BE DEFLECTED NORTHWEST
BY THE RIDGE TO OUR NORTHEAST. WHILE THERE REMAINS A WEAK RIDGE/COL
AT MID-LEVELS...THE GFS DOES SHOW A TROUGH A 250MB PASSING
SOUTHEASTWARD ACROSS THE STATE WEDNESDAY/THURSDAY. THIS WILL HELP TO
KEEP THE ATMOSPHERE INVERSION FREE...WHICH COMBINED WITH THE
AVAILABLE MOISTURE WILL MAINTAIN A POTENTIAL FOR HEAVY SHOWERS.
GFS/ECMWF SHOW A 500MB THERMAL TROUGH PASSING ACROSS THE STATE WITH
THE UPPER TROUGH...WITH 500MB TEMPERATURES OF -10C/-9C RESPECTIVELY.

GFS/ECMWF BOTH SHOW THE RIDGE BEING DISPLACED SOUTH OF THE STATE
THIS WEEKEND...WITH AT LEAST ONE COLD FRONT SWEEPING IN FROM THE
NORTHWEST. THERE IS SOME DISAGREEMENT AS TO TIMING AND HOW FAR SOUTH
THE BOUNDARY WILL MAKE IT AND HOW DEEP WE GET INTO THE WESTERLIES...
BUT THAT IS TO BE EXPECTED THIS FAR OUT IN TIME. CURRENT FORECAST
INCLUDES SOME FORM OF KONA WINDS AND ABOVE NORMAL CHANCES FOR
PRECIPITATION...WHICH STILL LOOK ON TRACK.

&&

.MARINE...
THE SWELL AT BUOY 51001 HAS ALREADY BEGUN TO DROP...HAVING PEAKED
AT 8 FT OVERNIGHT. COMBINED SEAS AT THE WAIMEA BAY BUOY HAVE CLIMBED
TO 5 FT...WHICH IS STILL A FEW FEET BELOW WAVEWATCH III GUIDANCE.
LOWERED SURF HEIGHTS AND SWELLS IN THE COASTAL WATERS FORECAST FOR
TODAY. THE NEXT SWELL IS EXPECTED TO ARRIVE ON WEDNESDAY...AND THIS
COULD REACH ADVISORY LEVELS FOR BOTH HIGH SURF AND SMALL CRAFTS.

&&

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

&&

BRAVENDER

CORRECTED MARINE SECTION BUOY NUMBER