High Surf in Hawaii, February 19 to 23, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
345 AM HST SUN FEB 19 2012

.SYNOPSIS...
TRADE WINDS WILL REMAIN BREEZY TODAY...WITH ENHANCED SHOWERS RIDING
IN ON THE TRADE WINDS. RAINFALL WILL FOCUS OVER WINDWARD AREAS...
WITH SOME BRIEFLY HEAVY SHOWERS...BUT SOME SHOWERS WILL ALSO AFFECT
THE LEEWARD SIDES. WINDS WILL DECREASE SLIGHTLY MONDAY AND
TUESDAY...WITH ENHANCED TRADE SHOWERS PERSISTING INTO WEDNESDAY...
ESPECIALLY OVER WINDWARD BIG ISLAND. ALTHOUGH DRIER TRADE WIND
CONDITIONS ARE EXPECTED FOR THE SECOND HALF OF THE WEEK...WETTER
WEATHER IS POSSIBLE NEXT WEEKEND.

&&

.DISCUSSION...
CURRENTLY...RELATIVELY STRONG SURFACE HIGH PRESSURE /1034 MB/
CENTERED ABOUT 1100 MILES TO THE NE IS PROVIDING BRISK TRADE WINDS
TO THE ISLANDS AND SURROUNDING WATERS. A NEARLY STATIONARY CLOSED
LOW ALOFT...SEEN ON WATER VAPOR IMAGERY SW OF THE ISLANDS NEAR 18N
161W...HAS BROUGHT COLDER THAN NORMAL TEMPERATURES TO THE MID AND
UPPER ATMOSPHERE...RESULTING IN FAIRLY SIGNIFICANT ATMOSPHERIC
INSTABILITY...AND AREAS OF BROKEN TO OVERCAST HIGH CLOUDS. A BAND OF
INCREASED LOW LEVEL MOISTURE EMBEDDED WITHIN THE TRADE FLOW HAS BEEN
TRAVERSING THE ISLAND CHAIN FOR MUCH OF THE NIGHT...AND SOAKING
WINDWARD PORTIONS OF ALL ISLANDS WITH SOME BRIEFLY HEAVY SHOWERS...
ESPECIALLY MAUI AND THE BIG ISLAND...WITH LIGHTNING REPORTED NEAR
HILO A LITTLE AFTER 2 AM. OVER THE BIG ISLAND SUMMITS...SUB-FREEZING
TEMPERATURES ARE IN THE LOW 20/S...AND MOISTURE EXTENDING ABOVE THE
SUMMIT LEVEL IS LIKELY BRINGING A WINTRY MIX OF PRECIP...PRIMARILY
FREEZING RAIN...AND A WINTER STORM WARNING REMAINS IN EFFECT DUE TO
THE ASSOCIATED HAZARDS. WINDS OVER HALEAKALA REMAIN SUSTAINED ABOVE
30 MPH...AND THE ONGOING WIND ADVISORY HAS BEEN EXTENDED THROUGH
TONIGHT.

GFS AND ECMWF BOTH DEPICT A SLIGHT DRYING TREND BY THIS
AFTERNOON...AS THE BAND OF LOW LEVEL MOISTURE WORKS ITS WAY
WESTWARD. STILL EXPECT PASSING SHOWERS AND RELATIVELY CLOUDY SKIES
AS THE TRADE WINDS FORCE MOISTURE UP THE SLOPES IN AN UNSTABLE
ATMOSPHERE. HAVE ADDED ISOLATED THUNDERSTORMS TO THE MORNING
FORECAST FOR WINDWARD MAUI AND WINDWARD BIG ISLAND...AND ADJACENT
COASTAL WATERS...AND A CHANCE OF THUNDERSTORMS OVER LEEWARD AND
INTERIOR PORTIONS OF THE BIG ISLAND FOR THIS AFTERNOON...AS DAYTIME
HEATING PROVIDES A FOCUS.

THE TRADE WINDS WILL DROP A NOTCH ON MONDAY OVER THE SMALLER
ISLANDS...AS A COLD FRONT APPROACHING FROM THE NW DECREASES THE
PRESSURE GRADIENT W OF THE ISLANDS...AND TURNS WINDS TO THE ESE.
MODERATE TO FRESH TRADE WINDS WILL REMAIN HOWEVER THROUGH MOST OF
THE WEEK...ESPECIALLY OVER COASTAL WATERS E OF THE ISLANDS...AS THE
FRONT WEAKENS AND NEW HIGH PRESSURE PASSES N OF THE ISLANDS. LATEST
MODEL RUNS DEPICT SOME WEAKENING OF THE TRADES TOWARD THE END OF THE
WEEK...AS ANOTHER LOW ALOFT DEVELOPING NEAR THE ISLANDS INCREASES
THE POTENTIAL FOR WET WEATHER.

WHILE THE CURRENT UPPER LEVEL LOW IS FORECAST TO DRIFT E...MOVING
OVER THE BIG ISLAND THROUGH TONIGHT...AND E OF THE ISLANDS MONDAY
AND TUESDAY...THE ASSOCIATED MID LEVEL LOW IS EXPECTED TO LINGER SE
OF THE BIG ISLAND THROUGH MID-WEEK. END RESULT WILL BE A TREND
TOWARD DRIER TRADE WIND WEATHER OVER THE SMALLER ISLANDS...WITH A
WETTER THAN NORMAL TRADE WIND WEATHER PATTERN REMAINING OVER THE BIG
ISLAND.

&&

.AVIATION...
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT THE LEEWARD TERMINALS...
BUT MVFR CIG/VIS...AND ISOL IFR CIG/VIS...WILL AFFECT WINDWARD
SLOPES OF ALL ISLANDS...AND WINDWARD TERMINALS LIKE PHTO AND PHLI.
AIRMET TANGO IS IN PLACE FOR LOW LEVEL TURB TO THE S AND W
OF THE MTS OF ALL ISLANDS...DUE TO STRONG TRADE WINDS. AIRMET SIERRA
HAS BEEN ISSUED FOR MT OBSC ON MAUI AND THE BIG ISLAND...AND AIRMET
ZULU IS ALSO IN EFFECT FOR AREAS AROUND MAUI AND THE BIG
ISLAND...FOR LIGHT TO MODERATE RIME ICING.

&&

.MARINE...
STRONG TRADE WINDS AND ASSOCIATED SEAS HAVE PROMPTED AN EXTENSION
OF THE SMALL CRAFT ADVISORY /SCA/ FOR ALL WATERS. THE MOKAPU BUOY E
OF OAHU IS REPORTING COMBINED SEAS NEAR 10 FT...WITH A PRIMARY
PERIOD NEAR 10 SECONDS...AS IS THE PAUWELA BUOY IN THE COASTAL
WATERS N OF KAHULUI...AND CHOPPY SHORT-PERIOD SURF ALONG E FACING
SHORES IS LARGE ENOUGH TO WARRANT A HIGH SURF ADVISORY. ALTHOUGH
TRADES ARE EXPECTED TO EASE OVER AND W OF THE ISLANDS EARLY IN THE
NEW WEEK...A LONG FETCH OF TRADE WINDS TO THE E WILL MAINTAIN THE
SHORT-PERIOD TRADE SWELL FOR MUCH OF THE WEEK...WITH LATEST WWIII
GUIDANCE INDICATING THAT COMBINED SEAS WILL STAY ABOVE THE 10 FT SCA
CRITERION UNTIL FRIDAY. BOTH THE HIGH SURF ADVISORY AND SCA HAVE
BEEN EXTENDED...AS WINDS AND SEAS WILL REMAIN HIGH THROUGH AT LEAST
MONDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST MONDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

WINTER STORM WARNING UNTIL 6 AM HST MONDAY FOR BIG ISLAND SUMMITS.

WIND ADVISORY UNTIL 6 AM HST MONDAY FOR HALEAKALA SUMMIT.

SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR ALL HAWAIIAN WATERS.

&&

BIRCHARD