000
FXHW60 PHFO 121930
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
930 AM HST FRI MAR 12 2010

.SYNOPSIS...
EASTWARD MOVING HIGH PRESSURE WILL LEAD TO WEAKENING TRADE WINDS AND
A DRIER WINDWARD FOCUSED SHOWER PATTERN THROUGH SATURDAY. TRADE
WINDS STRENGTHEN AGAIN SUNDAY AND MONDAY WITH INCREASING WINDWARD
SHOWERS AS WEAK FRONT REACHES THE AREA MONDAY MORNING. WINDS
DIMINISH AGAIN TUESDAY AND WEDNESDAY AHEAD OF ANOTHER COLD FRONT
THAT WILL REACH KAUAI WEDNESDAY AFTERNOON. A WETTER TRADE WIND
PATTERN WILL RESUME THURSDAY.

&&

.DISCUSSION...
HIGH PRESSURE N OF THE STATE WILL KEEP FRESH TRADES IN GEAR THROUGH
THIS AFTERNOON AS IT SLIDES E. 12/12Z SOUNDINGS AND PWAT IMAGERY
REVEAL HAWAII REMAINS SITUATED IN A WEDGE OF RELATIVELY DRY AIR WITH
ANY FRONTAL OR ITCZ WELL OUT OF REACH TO THE N AND S RESPECTIVELY.
BROAD OCCLUDING LOW PRESSURE N OF HAWAII WILL FURTHER DISPLACE HIGH
PRESSURE TO THE E LEADING TO DIMINISHING TRADES THROUGH SAT. DRY
STABLE AIR AND WEAKER TRADES WILL KEEP ISOL/SCT SHOWERS BETTER
FOCUSED OVER WINDWARD TERRAIN TODAY/SAT.

SUN/MON INCREASING TRADES ALONG WITH SUBTLE FALLS IN 500 MB HEIGHTS
WILL PRODUCE A WETTER TRADE PATTERN AS AN APPROACHING WEAK FRONT
REACHES THE NORTHERN PORTION OF THE STATE EARLY MON MORNING. HIGH
PRESSURE WILL REMAIN TRANSIENT PASSING N OF THE STATE. WINDS BECOME
VARIABLE TUE/WED AS ANOTHER POTENT SHORT WAVE OCCLUDES N OF THE
STATE. THIS WILL INDUCE A LIGHT WIND PATTERN AND VARIABLE LAND/SEA
BREEZES TUE INTO WED AHEAD OF THE ATTENDANT WEAK FRONT SLATED TO
REACH KAUAI WED.

HAVE REASONABLE CONFIDENCE RETURNING TRADES LATE WED INTO THU AND
HOLDING THROUGH THE REMAINDER OF THE PERIOD. GUIDANCE REMAINS IN
FAIR AGREEMENT WITH THE OVERALL HEIGHT PATTERN SUGGESTING SOME
DEGREE OF CYCLONIC FLOW ALOFT AND MID LEVEL DESTABILIZATION. COUPLED
WITH FRESH/STRONG TRADES...THIS WILL LEAD TO A WETTER WINDWARD
PRECIP PATTERN AGAIN FOR THE SECOND HALF OF NEXT WEEK WITH LOCALLY
HEAVY SHOWERS POSSIBLE.

&&

.PREVIOUS DISCUSSION.../ISSUED 400 AM HST FRI MORNING/
HIGH PRESSURE NORTH OF THE STATE IS CURRENTLY BRINGING BREEZY TRADES
TO THE STATE. RIDGING WILL BE FORCED SOUTHWARD TO ONLY ABOUT 300
MILES NORTH OF THE ISLANDS BY THIS EVENING...LOWERING WINDS TO
MODERATE STRENGTH. THERE ARE INDICATIONS THAT WINDS ARE ALREADY
STARTING TO WEAKEN...WITH SURFACE PRESSURE DECREASING AND OVERALL
WIND SPEEDS ON THE DOWNWARD TREND. MODELS SEEM TO SUGGEST THAT THE
FRONT WILL BE TOO WEAK TO MAKE IT THROUGH THE ISLAND CHAIN...WITH
THE FEATURE STALLING AS IT REACHES KAUAI. MODELS ALSO INDICATE THAT
PRE-FRONTAL MOISTURE WILL BE BROUGHT UP OVER THE ISLANDS SUNDAY AND
MONDAY. WITH TRADE WINDS CONTINUING...SHOWERS WILL AFFECT MAINLY
WINDWARD AND MOUNTAIN SLOPES.

THERE HAS BEEN LESS SHOWER ACTIVITY OVERNIGHT COMPARED TO WEDNESDAY
NIGHT...WITH RAIN GAGE REPORTS SHOWING SPARSE AND LIGHT RAINFALL
ACCUMULATIONS. UPPER LEVEL RIDGING IS CAUSING INCREASED SUBSIDENCE
OVER THE ISLANDS. THE ATMOSPHERE HAS BECOME MORE STABLE AS A
RESULT...WITH THE 12Z SOUNDINGS FROM LIHUE AND HILO SHOWING LOW
LEVEL INVERSIONS CONTINUING TO DECREASE IN HEIGHT...AT ABOUT 6400
AND 7500 FT RESPECTIVELY. WITH THE LOWER INVERSION HEIGHTS LIMITING
THE VERTICAL DEVELOPMENT OF CLOUDS...THE CHANCES OF HEAVY RAIN
OCCURRING FROM SHOWERS IS LOW. PRECIPITABLE WATER VALUES ARE ALSO
LOW...AT AROUND 1 INCH. THE OVERALL TREND IS FOR INCREASED STABILITY
FOR THE NEXT COUPLE DAYS UNTIL THE FRONT MENTIONED EARLIER GETS
CLOSE TO THE STATE LATE SUNDAY. ALTHOUGH RAINFALL ACCUMULATIONS WILL
BE LIGHT...THERE IS ENOUGH MOISTURE FOR TRADE SHOWERS TO REMAIN
PRESENT...BECOMING MORE ACTIVE DURING THE NIGHT AND MORNING HOURS.

HIGH PRESSURE WILL MOVE IN BEHIND THE FRONT MONDAY...WHICH WILL
CAUSE TRADE WINDS TO STRENGTHEN...BECOMING BREEZY. RIDGING WILL MOVE
OVER THE STATE TUESDAY AFTERNOON...WEAKENING THE WINDS TO LIGHT AND
VARIABLE. MODELS SHOW ANOTHER FRONT APPROACHING THE ISLANDS TUESDAY
AFTERNOON.

&&

.AVIATION...
VFR CONDS EXP FOR THE TERMINALS THRU THE TAF PERIOD. ANY MVFR
CIGS/VIS WILL BE CONFINED TO WINDWARD/MT TERRAIN. AIRMET TANGO FOR
LLVL MOD TURB S THRU W OF ALL ISLANDS CONT INTO THIS AFTN.
ADDITIONALLY...THE SUBTROPICAL JET IS PRODUCING MOD TURB BTN
FL300/FL370 DIRECTLY OVER THE ISLANDS. THIS IS ALSO EXP TO CONT
BEYOND 22Z INTO THIS AFTN.

&&

.MARINE...
WINDS ARE ON THE DECREASE TODAY. THE SMALL CRAFT ADVISORY IS SET TO
EXPIRE THIS EVENING. NOT ANTICIPATING ANY CHANGES SO WILL LIKELY
CANCEL IT WITH THE AFTERNOON FORECAST ISSUANCE.

GENERALLY SMALL SURF EXPECTED AROUND THE STATE TODAY...WITH EVEN A
MINOR BUMP ALONG S FACING SHORES. NW SWELL BUILDS SAT TO JUST
OVERHEAD ALONG N FACING SHORES. LARGER NW SWELL SHOWS SUN REACHING
THE 10 TO 12 FT RANGE OR ROUGHLY DOUBLE OVERHEAD WITH POTENTIALLY
SOME LARGER SETS TOWARDS SUNSET. THIS SWELL WILL REACH ADVISORY
LEVELS OF 15 TO 20 FT INTO MON. SURF LEVELS OFF BELOW ADVISORY
LEVELS MID WEEK BUT REMAINS SIZEABLE. NW SWELL JUMPS OVER THE
ADVISORY THRESHOLD AGAIN DURING THE SECOND HALF OF NEXT WEEK. S
FACING SHORES WILL SEE A DECENT SHOT OF SOUTHERN HEMI SWELL SHOWING
TUE. TOP AREAS SHOULD PULL IN SOME CHEST/SHOULDER HIGH SURF.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR ALL HAWAIIAN
WATERS-

&&

$$

PUBLIC/AVIATION/MARINE...DEJESUS
PREVIOUS...HARRISON/BIRCHARD

NWS HFO Office Area Forecast Discussion