FXHW60 PHFO 251332
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
332 AM HST WED NOV 25 2009
.SYNOPSIS...
HIGH PRESSURE BUILDING NORTH OF THE ISLANDS WILL BRING INCREASED
TRADE WINDS TODAY...WITH TRADE WINDS REMAINING QUITE BREEZY INTO THE
HOLIDAY WEEKEND. THE STRONGER TRADE WINDS WILL ALSO BRING AN UPTICK
IN TRADE SHOWERS OVER WINDWARD AND MAUKA AREAS...ESPECIALLY FROM
TONIGHT INTO FRIDAY.
&&
.DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS THE LEADING EDGE OF A FRONTAL CLOUD
BAND ABOUT 200 MILES NORTHWEST OF KAUAI THIS MORNING...MOVING
SOUTHEAST AT LESS THAN 10 MPH. EAST OF THE ISLANDS...SCATTERED TO
BROKEN LOW CLOUDS ARE APPROACHING THE ISLANDS IN A MODERATE TRADE
WIND FLOW...BUT RADAR SHOWS LITTLE SIGNIFICANT PRECIPITATION
EMBEDDED IN THEM. MORNING SOUNDINGS CONTINUE TO SHOW A STABLE AIR
MASS IN PLACE OVER THE ISLANDS...WITH PWAT VALUES BELOW AN INCH IN
THE PHLI SOUNDING. THEREFORE...LOTS OF LEEWARD SUN TODAY...AND A FEW
WINDWARD SHOWERS.
THE FRONTAL MOISTURE NORTHWEST OF KAUAI IS NOT EXPECTED TO REACH
THE ISLANDS...AND WILL STALL ALONG 25N TODAY AND TONIGHT...AS HIGH
PRESSURE FOLLOWING THE BOUNDARY MOVES QUICKLY EAST...AND ELIMINATES
ANY SOUTHWARD MOMENTUM THE BOUNDARY CURRENTLY HAS. THE PASSAGE OF
THE HIGH WILL ACT TO TIGHTEN THE LOW-LEVEL PRESSURE GRADIENT OVER
THE ISLANDS...AND INCREASING TRADE WINDS ARE EXPECTED TODAY. TRADES
ARE EXPECTED TO PEAK THURSDAY AND THURSDAY NIGHT BEFORE SLOWLY
EASING AS WE HEAD INTO THE WEEKEND...AS THE HIGH TEMPORARILY
ESTABLISHES ITSELF IN A CLIMATOLOGICAL POSITION FAR NORTHEAST OF THE
ISLANDS.
A MID-LEVEL RIDGE CURRENTLY OVER THE ISLANDS WILL GRADUALLY WEAKEN
OVER THE NEXT 24 HOURS...AS A MID- AND UPPER-LEVEL TROUGH DROPPING
DOWN FROM THE NORTHWEST SHARPENS OVER THE ISLANDS TONIGHT THROUGH
FRIDAY...BEFORE DISSIPATING AND MOVING EAST THIS WEEKEND. EXPECT
THAT THIS TROUGH WILL ACT TO SLIGHTLY DESTABILIZE THE ATMOSPHERE...
RESULTING IN A DEEPER MARINE LAYER. THIS WILL LIKELY MEAN AN
INCREASE IN THE NUMBER AND INTENSITY OF TRADE SHOWERS...WITH THE
SHOWERS SPREADING SOME LIMITED MOISTURE LEEWARD IN THE INCREASED
TRADE FLOW.
THE EXTENDED PICTURE IS SIMILAR TO THAT EXPRESSED IN EARLIER
DISCUSSIONS...AND SIMILAR TO THE CURRENT SCENARIO CURRENTLY
UNFOLDING. ANOTHER FRONT WILL APPROACH FROM THE NORTHWEST SATURDAY
NIGHT AND SUNDAY...WITH A FOLLOWING HIGH PASSING WELL NORTH OF THE
ISLANDS ON SUNDAY AND MONDAY. WHILE MOISTURE ASSOCIATED WITH THE
NEXT FRONT IS ALSO DEPICTED AS REMAINING NORTH OF THE ISLANDS...
ANOTHER PROGRESSIVE MID-LEVEL TROUGH WILL PASS OVER THE ISLANDS FROM
THE NORTHWEST...POSSIBLY ADDING TO THE VIGOR OF TRADE SHOWERS ON
SUNDAY. THE DEPARTURE OF THE TROUGH TO THE EAST WILL MEAN FEWER
SHOWERS MONDAY AND TUESDAY...BUT SURELY THIS FORECAST WILL NEED TO
BE FINE TUNED AS THE WEEKEND NEARS.
&&
.MARINE...
THE ANTICIPATED LARGE NORTHWEST SWELL HAS ARRIVED AT BUOY 51101 TO
THE NORTHWEST OF KAUAI...WITH NO DATA FROM BUOY 51001 SINCE 10 PM
LAST NIGHT. PEAK SWELL HEIGHTS THUS FAR HAVE BEEN NEAR 16 FEET. THE
CDIP WAIMEA BUOY LOCATED OFF OAHU/S NORTH SHORE SHOWED A RAPID RISE
IN SIGNIFICANT WAVE HEIGHTS BETWEEN MIDNIGHT AND 2 AM...AND THE
SWELL APPEARS TO BE BEHAVING AS EXPECTED. SURF IS STILL EXPECTED TO
RISE RAPIDLY THIS MORNING ALONG NORTH AND WEST FACING SHORES OF MOST
ISLANDS...AND A HIGH SURF WARNING REMAINS IN EFFECT FOR NORTH AND
WEST FACING SHORES OF NIIHAU KAUAI OAHU AND MOLOKAI...AND FOR NORTH
FACING SHORES OF MAUI.
WITH BUOY OBS SHOWING THE SWELL COMING IN FROM 330-340 DEGREES...
MOST OF THE ENERGY WILL BE BLOCKED FROM REACHING THE BIG ISLAND...
BUT SOME INCREASE IN SURF IS EXPECTED ALONG THE KONA SIDE THIS
AFTERNOON AND TONIGHT. GIVEN THE SLIGHTLY MORE NORTHERLY ANGLE TO
THE SWELL...HAVE ELECTED TO NOT ISSUE AN ADVISORY AT THIS POINT.
POSSIBLY MORNING SURF OBSERVATIONS FROM THE AROUND THE STATE WILL
HELP US TO DETERMINE WHETHER AN ADVISORY IS NECESSARY.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR BOTH THE LARGE NORTHWEST
SWELL AND FOR INCREASING TRADE WINDS.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR ALL HAWAIIAN WATERS.
HIGH SURF WARNING FOR NORTH AND WEST FACING SHORES OF NIIHAU KAUAI
OAHU AND MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI.
&&
$$
BIRCHARD
