FXHW60 PHFO 011342
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
342 AM HST TUE DEC 1 2009
.SYNOPSIS...
NORTHEAST WINDS WILL DELIVER A FEW WINDWARD SHOWERS TO KAUAI AND
OAHU THIS MORNING...BUT WINDS WILL WEAKEN LATER TODAY...BECOMING
LIGHT AND VARIABLE TONIGHT THROUGH WEDNESDAY NIGHT. WITH THE LIGHT
AND VARIABLE WINDS...WEATHER WILL BE MOSTLY DRY...WITH ONLY ISOLATED
SHOWERS EXPECTED. AN APPROACHING FRONT WILL BRING SOUTHWEST WINDS ON
THURSDAY...WITH THE FRONT BRINGING CLOUDS AND SHOWERS AS IT MOVES
DOWN THE ISLAND CHAIN THURSDAY NIGHT AND FRIDAY. THE FRONT WILL
STALL AND WEAKEN NEAR THE ISLANDS ON SATURDAY AND SUNDAY...WITH
ANOTHER FRONT APPROACHING EARLY NEXT WEEK.
&&
.DISCUSSION...
SATELLITE IMAGERY CONTINUES TO HIGHLIGHT A WEAKENING NE TO SW
ORIENTED WEDGE OF MOISTURE OVER WATERS AROUND KAUAI AND OAHU THIS
MORNING...WITH A FEW SHOWERS ASSOCIATED WITH THIS OLD FRONTAL
BOUNDARY MOVING OVER WINDWARD PORTIONS OF THESE ISLANDS. LITTLE IN
THE WAY OF SHOWERS ARE EXPECTED OVER MAUI AND THE BIG ISLAND...
DESPITE THE DEEP LAYER MOISTURE LURKING SE OF THE BIG ISLAND.
LOW CLOUDS AND SHOWERS NEAR THE ISLANDS ARE MOVING SW...THANKS TO
WEAKENING SURFACE HIGH PRESSURE TO THE NE AND WEAK SURFACE
TROUGHING E OF THE ISLANDS ALONG 150W. THESE WINDS WILL NOT LAST
PAST TODAY THOUGH...AS A DYNAMIC WEATHER PATTERN IS IN THE WORKS.
LATEST FORECAST MODELS CONTINUE TO DEPICT A SEASONABLE WEATHER
PATTERN FOR HAWAII OVER THE NEXT WEEK...CONSIDERING THAT IS DECEMBER
OF AN EL NINO YEAR.
AS FAR AS THE BIG PICTURE...A ZONAL JET STREAM WILL CARRY POWERFUL
FAST MOVING LOWS FROM WEST TO EAST ACROSS THE NORTH PACIFIC OVER THE
NEXT 7 TO 10 DAYS...WITH FRONTS ASSOCIATED WITH THESE LOWS TO
APPROACH...AND POSSIBLY MOVE DOWN...THE ISLAND CHAIN WITH LITTLE
SIGNIFICANT SUPPORT ALOFT. FIRST FRONT IS EXPECTED TO FALL APART N
OF KAUAI ON WEDNESDAY...THE SECOND IS EXPECTED TO MOVE DOWN AT LEAST
A PART OF THE ISLAND CHAIN FROM THURSDAY NIGHT INTO THE WEEKEND...
WITH A THIRD APPROACHING LATE THIS WEEKEND...AND POSSIBLY
ACCOMPANYING A GIANT NW SWELL WHEN IT NEARS EARLY NEXT WEEK. WITH
THE FAST FLOW ALOFT...TIMING ON THESE FEATURES...AND THEIR POSSIBLE
IMPACTS ON THE ISLANDS...WILL BE SUBJECT TO MODIFICATION AS MODELS
TRY TO KEEP PACE WITH THE ATMOSPHERE.
AS FAR AS THE DETAILS...HIGH PRESSURE TO THE NE WILL MOVE QUICKLY E
AND DISSIPATE TODAY...AS A FRONT AND LOW TAKE IT/S PLACE TO OUR N.
THUS WINDS WILL WEAKEN PRETTY DRAMATICALLY TODAY...AND RECENT OBS
AND 24-HOUR PRESSURE TRENDS /DOWN OVER 2 MB STATE WIDE/ SUPPORT THIS
NOTION. THE FRONT WILL APPROACH AND STALL OVER WATERS JUST N OF
KAUAI TONIGHT AND WEDNESDAY...BUT IT/S PROXIMITY AND WEAK LOW-LEVEL
CONVERGENCE TO IT/S S WILL LIKELY HELP TO FUEL A FEW MAINLY OCEANIC
SHOWERS...BUT THEIR EXTENT AND INTENSITY WILL BE LIMITED DUE TO A
STABILIZING MID- AND UPPER-LEVEL FLOW.
WITH A WEAK SURFACE PRESSURE GRADIENT FROM TONIGHT THROUGH WEDNESDAY
NIGHT...LAND AND SEA BREEZES WILL DOMINATE THE WIND FLOW OVER THE
ISLANDS...WITH THE OVERALL PATTERN FAVORING AFTERNOON AND EVENING
INTERIOR CLOUDS...AND MOSTLY CLEAR MORNINGS AND NIGHTS. THE AIRMASS
WILL BE DRY AND STABLE THROUGH THIS PERIOD...WITH LITTLE IN THE WAY
OF RAINFALL EXPECTED FROM THE DIURNAL ISLAND SCALE CIRCULATIONS.
A NEWLY APPROACHING FRONT WILL BRING A WIND SHIFT TO THE SW ON
THURSDAY...WITH THE FRONT EXPECTED TO MOVE DOWN AT LEAST A PORTION
OF THE ISLAND CHAIN THURSDAY NIGHT AND FRIDAY. WEAK MID-LEVEL
SUPPORT WILL ALLOW A BAND OF CLOUDS AND SHOWERS TO ACCOMPANY THE
FRONT...WITH A BRIEF PERIOD OF N WINDS BEHIND IT. THE FRONT IS
FORECAST TO STALL AND WEAKEN OVER MAUI COUNTY AND THE BIG ISLAND ON
FRIDAY NIGHT AS THE SUPPORT ALOFT LIFTS OFF TO THE NE. LINGERING
MOISTURE FROM THE FRONT IS DEPICTED AS BEING SLOW TO CLEAR THE
ISLANDS THIS WEEKEND...DESPITE LITTLE TO NO SUPPORT ALOFT.
WINDS WILL QUICKLY EASE BEHIND FRIDAY/S FRONT AS THE RIDGE SETTLES
OVER THE ISLANDS AGAIN...WITH LIGHT WINDS ON SATURDAY. WINDS WILL
BECOME SW AGAIN ON SUNDAY AS THE THIRD FRONT APPROACHES LATE THIS
WEEKEND. TOO SOON FOR DETAILS ON THIS ONE...BUT WORTH NOTING THAT
LONGER RANGE WAVE MODEL GUIDANCE HAS SEAS APPROACHING 50 FEET NEAR
THE CORE OF THE PARENT LOW...AND DEPICTS A VERY LARGE NW SWELL
BUILDING AT BUOY 51001 IN THE SUNDAY/MONDAY TIME FRAME.
&&
.MARINE...
NNW SWELL AND SHORTER PERIOD NNE SWELL ARE ON THE DECLINE THIS
MORNING...AND WITH WINDS ON THE DECLINE AS WELL...COMBINED SEAS
MEASURED AT LOCAL BUOYS ARE ON AN EXPECTED STEADY DOWN TREND. THUS
THE SMALL CRAFT ADVISORY /SCA/ AND HIGH SURF ADVISORY /HSA/ HAVE
JUST BEEN CANCELLED.
PLENTY MORE IN THE WAY OF NW SWELL MEANS THAT BOTH THESE FLAGS WILL
NEED TO BE HOISTED AGAIN SOON... WITH THE FIRST OF SEVERAL SOLID NW
SWELLS BUILDING ON WEDNESDAY. THIS SWELL WILL RESULT IN SURF ABOVE
ADVISORY LEVELS ALONG N AND W FACING SHORES OF MOST ISLANDS...AND
COMBINED SEAS ABOVE 10 FEET IN MOST MARINE ZONES. THE DISCUSSION
PORTION OF THE OAHU SURF FORECAST /SRFHFO/ HAS DETAILS ON THE
EXPECTED SWELLS THAT CAN BE LOOSELY APPLIED TO OTHER MARINE ZONES.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
BIRCHARD
