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Hawaiian Islands Synoptic Discussion and Guidance

153
FXHW60 PHFO 230556
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
800 PM HST SUN NOV 22 2009

.SYNOPSIS...
HIGH PRESSURE NORTHEAST OF THE STATE WILL SHIFT FURTHER EAST
ALLOWING TRADE WINDS TO DROP TO MODERATE LEVELS EARLY THIS WEEK.
TRADE WINDS WILL INCREASE AGAIN MID WEEK. SHOWERS WILL REMAIN
FOCUSED ON WINDWARD AND MOUNTAIN TERRAIN OVER THE NEXT SEVERAL DAYS.

&&

.DISCUSSION...
NOT EXPECTING ANY SIGNIFICANT CHANGES TO THE BENIGN TRADE WIND
PATTERN FROM THE DAY SHIFT. WATER VAPOR IMAGERY DEPICTS A
SOUTHEASTWARD MOVING SHEAR AXIS OVER THE ISLANDS. THIS IS
CONTRIBUTING TO SOME MINOR INSTABILITY WELL ABOVE 15 KFT...WHICH IS
WELL OUT OF REACH OF THE LOCALLY LIMITED MOISTURE IN THE WELL CAPPED
BOUNDARY LAYER. BLENDED TOTAL PRECIPITABLE WATER IMAGERY REVEALS
GENERALLY DRY AIR UPSTREAM WITH HAWAII...WHICH IS SITTING JUST
OUTSIDE THE NORTHERN FRINGE OF THE RICH TROPICAL ITCZ MOISTURE TO
THE SOUTH. SOME OF THIS MOISTURE MAY GRAZE THE STATE LATE TUESDAY
THROUGH THURSDAY. HOWEVER...WITH STABLE THERMODYNAMIC PROFILES
EXPECTED TO PERSIST...THIS WILL LIMIT THE VERTICAL DEVELOPMENT OF
ANY SHOWERS KEEPING THEM WINDWARD TERRAIN FOCUSED MID WEEK.

TRADES WILL WEAKEN SLIGHTLY DURING THE FIRST HALF OF THE WEEK AS
HIGH PRESSURE TO OUR NORTHEAST IS DISPLACED FURTHER EAST BY AN
AMPLIFYING DEEP LAYERED TROUGH TO THE NORTH. MID LATITUDE FLOW WILL
REMAIN PROGRESSIVE USHERING IN HEIGHT RISES AND SURFACE HIGH
PRESSURE TO OUR NORTH AGAIN BY MID WEEK ALLOWING TRADE WINDS TO
STRENGTHEN ONCE AGAIN. THIS WILL ALSO LIMIT THE EQUATORWARD REACH OF
ANY ATTENDANT FRONTAL ACTIVITY. REGARDLESS OF FLUCTUATING BATCHES
OF MOISTURE PASSING IN THE TRADES THE WEATHER WILL REMAIN PLEASANT
THROUGH THE FORECAST PERIOD.

&&

.PREVIOUS DISCUSSION.../ISSUED 400 PM HST SATURDAY/
PRECIPITATION THROUGH THE DAY HAS BEEN SPARSE...MOSTLY CONFINED TO
THE WINDWARD BIG ISLAND. SATELLITE IMAGERY SHOWS SOME SHOWER CLOUDS
UPWIND...WHICH IS TO THE EAST NORTHEAST OF THE MAIN HAWAIIAN
ISLANDS...THAT MAY COME ASHORE LATER TONIGHT. THE SHOWERS WOULD BE
LESS SIGNIFICANT THAN LAST NIGHT. AFTERNOON BALLOON SOUNDINGS ARE
STABLE AND RELATIVELY DRY.

&&

.MARINE...
THE CURRENT HIGH SURF ADVISORY FOR NORTH AND WEST KAUAI AND
NIIHAU...AS WELL AS NORTH SHORES OF OAHU MOLOKAI AND MAUI RUNS
THROUGH MONDAY NIGHT. IT IS POSSIBLE THE ADVISORY MAY BE EXTENDED
THROUGH TUESDAY.

LARGER SURF IS LIKELY LATE TUESDAY NIGHT INTO WEDNESDAY. SURF ALONG
NORTH FACING SHORES COULD REACH OR EXCEED THE 25 FOOT WARNING LEVEL
MARK FROM THE NORTHWEST. THIS WILL DROP SLOWLY INTO THE SECOND HALF
OF THE WORK WEEK...POSSIBLY FOLLOWED BY ANOTHER ADVISORY LEVEL SWELL
OVER THE WEEKEND.

SOUTH FACING SHORES WILL SEE CONTINUED WAIST TO SHOULDER HIGH
SOUTHERN HEMI SWELL MONDAY. A DECREASING TREND WILL BEGIN MONDAY
NIGHT THROUGH MID WEEK. MODEST SOUTHEAST SWELL WILL APPEAR DURING
THE SECOND HALF OF THE WEEK POSSIBLY HITTING THE CHEST HIGH MARK
ALONG THE BETTER EXPOSED REEFS/BEACHES.

&&

.AVIATION...
EXPECT VFR CONDITIONS TO PREVAIL FOR THE TERMINALS TONIGHT. TRADE
WINDS WILL FOCUS -SHRA OVER WINDWARD/MT TERRAIN OVERNIGHT WITH HIGH
END TRANSIENT MVFR CIGS/VIS. PHNY WILL COULD SEE THE USUAL
INTERMITTENT MVFR CIGS TOMORROW AFTERNOON DUE THE TO THE FIELD
ELEVATION. OTHERWISE...NO WIDESPREAD FLIGHT RESTRICTIONS ARE
EXPECTED THROUGH THE NEAR TERM.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST TUESDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU-MOLOKAI-MAUI
WINDWARD WEST-WINDWARD HALEAKALA.

&&

$$

PUBLIC/AVIATION...DEJESUS
MARINE...DEJESUS/HOAG
PREVIOUS...HOAG

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office

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