FXHW60 PHFO 220640
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
840 PM HST MON DEC 21 2009
.SYNOPSIS...
A SERIES OF WEAK FRONTS WILL PASS ACROSS THE ISLANDS OVER THE NEXT
SEVEN DAYS. BRIEF BOUTS OF LIGHT TO MODERATE TRADES WILL FOLLOW EACH
FRONTAL ENCOUNTER...WITH ANY FRONTAL SHOWERS EXPECTED TO FOCUS ON
WINDWARD AND MAUKA AREAS.
&&
.DISCUSSION...
THE SUBTROPICAL RIDGE EXTENDS SOUTHWEST FROM A 1027 MB HIGH NEAR
38N135W THROUGH 25N155W AND 22N180W THIS EVENING. LOWS PASSING
EASTWARD WITHIN THE WINTER MID LATITUDE STORM TRACK HAVE STEADILY
PUSHED THE RIDGE FARTHER AND FARTHER SOUTH OVER THE PAST
WEEK...WEAKENING IT IN THE PROCESS. THE COMING WEEK WILL SEE A
SERIES OF FRONTS PASSING ACROSS THE ISLANDS BEFORE WASHING OUT.
THESE FRONTS WILL BE WEAK AND WILL BE ACCOMPANIED BY BRIEF BOUTS OF
FRONTAL SHOWERS AND LIGHT TO MODERATE POST FRONTAL TRADE WINDS.
THE FIRST OF THESE FRONTS IS ABOUT 240 MILES NORTHWEST OF KAUAI AND
IS POISED TO REACH THAT ISLAND LATE TONIGHT OR TUESDAY...THEN
CONTINUE MOVING SOUTHEAST BEFORE STALLING IN THE VICINITY OF THE BIG
ISLAND TUESDAY NIGHT AND WEDNESDAY. WINDS AHEAD OF THE FRONT ARE
LIGHT...WITH WINDS ALREADY SHIFTING TO LIGHT NORTHWESTERLIES WEST OF
MOLOKAI. A FEW SHOWERS HAVE FORMED AHEAD OF THE FRONT ACROSS OAHU AS
MILD LOW LEVEL CONVERGENCE SETS UP WITHIN THE PREFRONTAL
ENVIRONMENT. WE EXPECT THIS ACTIVITY TO CONTINUE AND POSSIBLY
INCREASE IN COVERAGE...BUT WIDESPREAD HEAVY SHOWERS ARE NOT EXPECTED
TONIGHT GIVEN THE STABILITY OF OUR AIRMASS. REMNANT MOISTURE AND THE
PROXIMITY OF AN UPPER TROUGH EAST OF THE BIG ISLAND MAY ENHANCE SOME
FRONTAL SHOWERS OVER THEM TUESDAY NIGHT AND WEDNESDAY AS THE FRONT
STALLS.
POST FRONTAL TRADES WILL BE BRIEF AS THE WEAK FOLLOWING HIGH MOVES
EAST AND ANOTHER FRONT APPROACHES FROM THE NORTHWEST. WINDS WILL
AGAIN BE LIGHT AHEAD OF THE FRONT...WITH LAND AND SEA BREEZES
DOMINATING. THIS FRONT IS ALSO EXPECTED TO BE RATHER WEAK...REACHING
KAUAI THURSDAY AND PASSING ACROSS THE ISLAND CHAIN TO THE BIG ISLAND
THURSDAY NIGHT AND FRIDAY. SHOWERS WILL FAVOR NORTH AND NORTHEAST
FACING SLOPES AS TRADE WINDS BUILD BACK IN BEHIND THE FRONT.
A THIRD FRONT IS FORECAST TO APPROACH THE STATE SUNDAY OR MONDAY.
&&
.MARINE...
A SERIES OF MODERATE TO EXTREMELY LARGE SWELLS WILL AFFECT THE
ISLANDS THIS WEEK. THE CURRENT SWELL WILL PROVIDE BORDERLINE
ADVISORY LEVEL SURF THROUGH TONIGHT. A LARGER NORTHWEST SWELL WILL
BEGIN TO FILL IN TUESDAY...PEAK TUESDAY NIGHT OR EARLY WEDNESDAY
WITH HEIGHTS NEAR LOW END WARNING LEVELS...THEN GRADUALLY LOWER INTO
THURSDAY. A THIRD AND MUCH LARGER NORTHWEST SWELL IS EXPECTED TO
BEGIN FILLING IN ON THURSDAY...WITH WARNING LEVEL SURF EXPECTED
THURSDAY NIGHT AND FRIDAY. WAVEWATCH MODEL GUIDANCE SHOWS OPEN OCEAN
SWELL HEIGHTS OF AROUND 20 FEET WITH RATHER LONG PERIODS. THIS WOULD
PRODUCE WAVE HEIGHTS SIMILAR TO WHAT WE SAW A COUPLE OF WEEKS AGO.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST TUESDAY FOR NORTH AND WEST FACING
SHORES OF KAUAI AND NIIHAU...AS WELL AS FOR NORTH FACING SHORES OF
OAHU...MOLOKAI AND MAUI.
&&
$$
POWELL
