High Surf in Hawaii, March 1 to 2, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST WED FEB 29 2012

.SYNOPSIS...
HIGH PRESSURE FAR NORTHEAST OF HAWAII WILL MAINTAIN TRADE WINDS
UNTIL THIS WEEKEND. CURRENT FRESH TRADES WILL EASE OFF BY THURSDAY
NIGHT. SHOWERS RIDING IN ON THE TRADES WILL BE MOST ACTIVE DURING
THE NIGHT AND MORNING HOURS...FAVORING THE WINDWARD AND MAUKA AREAS.
SOME SHOWERS WILL BE HEAVIER...DUE TO A COOLER ATMOSPHERE ALOFT.

&&

.DISCUSSION...
A SURFACE HIGH NORTHEAST OF THE ISLANDS IS DRIVING FRESH EASTERLY
WINDS ACROSS THE EAST HALF OF THE STATE. A SURFACE TROUGH TO THE
WEST IS INDUCING EAST SOUTHEAST WINDS ACROSS KAUAI AND OAHU. THE
TROUGH IS ALSO GENERATING HEAVY SHOWERS AND THUNDERSTORMS...MOSTLY
WEST OF KAUAI. UPPER LEVEL WESTERLY WINDS ARE BLOWING DENSE HIGH
CLOUDS OVER THE ISLANDS FROM THE TOPS OF THE THUNDERSTORMS. THE HIGH
CLOUDS COULD LINGER INTO THURSDAY NIGHT.

COOLER THAN NORMAL TEMPERATURES ALOFT ASSOCIATED WITH AN UPPER LOW
NORTHWEST OF KAUAI IS KEEPING THE AIRMASS OVER THE STATE UNSTABLE.
ANOTHER UPPER LOW IS FORECAST TO FORM TO THE NORTHEAST...WHICH WILL
AID IN KEEPING TEMPERATURES ALOFT COOL AND SHOWERS ENHANCED THROUGH
THIS WEEKEND. THE TRADE WINDS WILL CARRY THE SHOWERS TO WINDWARD AND
MAUKA SECTIONS...WITH SOME PASSING OVER LEEWARD SECTIONS OF THE
SMALLER ISLANDS.

THE TRADE WINDS WILL DIMINISH THURSDAY NIGHT AS THE SURFACE HIGH TO
THE NORTHEAST MOVES AWAY TO THE EAST. ANOTHER LARGER HIGH WILL MOVE
EAST...ENDING UP NORTH OF THE ISLANDS THIS WEEKEND. THE HIGH WILL
PUSH A SHEARLINE ACROSS THE STATE. MODELS DISAGREE ON THE TIMING
AND IMPACT OF THE SHEARLINE...WITH THE ECMWF BRINGING THE FEATURE
DOWN THE ISLAND CHAIN ON SUNDAY AND SUNDAY NIGHT WHILE THE GFS MOVES
IT THROUGH SUNDAY NIGHT AND MONDAY.

BOTH MODELS DEPICT A DEVELOPMENT OF A STRONG SURFACE LOW NORTHEAST
OF THE STATE AS THE SHEARLINE PASSES ACROSS THE ISLANDS. THE ECMWF
DEVELOPS THE LOW FARTHER WEST THAN THE GFS...AND THUS CLOSER TO THE
STATE. IN SO DOING...IT WEAKENS THE PRESSURE GRADIENT AND SUBSEQUENT
STRONG WINDS THAT THE GFS IS PROJECTING TO OCCUR. WILL GET A BETTER
FEEL ON WHAT WILL HAPPEN IN A COUPLE OF DAYS.

&&

.AVIATION...
AN AIRMET IS UP FOR MOUNTAIN OBSCURATION OVER KAUAI DUE TO LOW
CLOUDS AND SHOWERS. AN AIRMET IS ALSO UP FOR MODERATE RIME ICING
AROUND KAUAI. MVFR CONDITIONS ARE POSSIBLE OVER WINDWARD SLOPES OF
THE OTHER ISLANDS. VFR CONDITIONS PREVAIL AT ALL TAF SITES...THOUGH
SOME SHOWERS MAY PRODUCE TEMPORARY MVFR CONDITIONS.

&&

.MARINE...
BRISK WINDS IN EXPOSED WATERS WILL RESULT IN ROUGH OCEAN CONDITIONS.
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT FOR MOST COASTAL WATERS
EITHER FOR WINDS OF AROUND 25 KT OR COMBINED SEAS OF 10 FEET. THE
SCA AND A HIGH SURF ADVISORY FOR EAST FACING SHORES SHOULD BOTH BE
GONE BY THURSDAY NIGHT.

THE WAVE WATCH III MODEL BASED ON THE GFS ATMOSPHERIC MODEL SHOWS A
VERY LARGE NORTHEAST SWELL ACROSS THE ENTIRE STATE SUNDAY NIGHT AND
MONDAY. THE ECMWF GLOBAL MODEL DISAGREES WITH GFS ON THE POSITION OF
THE LOW...HOWEVER...PUTTING THE SWELL OVER AND WEST OF KAUAI.
CONFIDENCE IN THE SURF FORECAST IS THEREFORE LOW.

&&

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

SMALL CRAFT ADVISORY UNTIL 6 AM HST THURSDAY FOR ALL HAWAIIAN WATERS
EXCEPT THE LEEWARD WATERS OF KAUAI OAHU AND MAUI COUNTY.

&&

CRAIG