368
FXHW60 PHFO 012002
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST SUN NOV 1 2009
SYNOPSIS
A CHANGE IN AIRMASS IS IN STORE AS A BOUNDARY NORTHWEST OF THE STATE
MOVES SOUTHEAST EARLY THIS WEEK. IT WILL BRING A PERIOD OF SHOWERS
MONDAY AND TUESDAY...FOLLOWED BY COOLER AIR BEHIND IT.
DISCUSSION
WATER VAPOR IMAGERY SHOWS A WEAKENING SHORTWAVE TROUGH 350 MILES
WEST NORTHWEST OF KAUAI...AND A STRONGER DEVELOPING SHORTWAVE 800
MILES NORTHWEST OF KAUAI. ACROSS THE FAR NORTHERN PACIFIC...ALONG
170W JUST SOUTH OF 50N...THERE IS ANOTHER SYSTEM THAT MAY HAVE AN
IMPACT ON THE STATE DURING THE SECOND HALF OF THE WEEK. VISIBLE AND
IR IMAGERY SHOWS A RAGGED BAND OF CLOUDS NORTHWEST OF KAUAI
ASSOCIATED WITH A WEAKENING STATIONARY FRONT...WITH MORE TYPICAL
TRADE CONDITIONS ACROSS THE STATE. 12Z SOUNDINGS FROM LIHUE AND HILO
SHOW INVERSIONS RUNNING 6-7KFT...WITH PRECIPITABLE WATERS RANGING
FROM 1.1 AT LIHUE TO 1.4 AT HILO. THE AMSU/SSMI BLENDED TOTAL
PRECIPITABLE WATER IMAGERY IS SIMILAR ACROSS THE STATE...WITH PW
VALUES INCREASING TO 1.6-1.8 INCHES IN A BAND ALONG THE OLD FRONT.
AS THE FARTHER NORTHWEST SYSTEM DIGS TOWARD THE STATE...IT WILL PICK
UP THE WEAKER SYSTEM HELP TO REINVIGORATE THE SURFACE FRONT. THE 12Z
GFS IS A BIT WEAKER AND SLOWER THAN EARLIER RUNS...BUT SHOWS THE
BOUNDARY REACHING KAUAI MONDAY NIGHT AND PROGRESSING DOWN THE ISLAND
CHAIN THROUGH TUESDAY NIGHT. WHILE THIS FEATURE LOOKS MORE LIKE A
SHEARLINE...WITH EASTERLY WINDS PRECEDING IT AND STRONGER
NORTHEASTERLY WINDS FOLLOWING IT...THERE IS A CHANGE IN AIRMASS
WITH 850MB TEMPERATURES DROPPING 2-3C BEHIND IT. WINDS WILL ALSO BE
STRONGER BEHIND THE BOUNDARY AS THE COOLER AIR MOVING ACROSS WARMER
WATER LEADS TO MORE UNSTABLE CONDITIONS AND GREATER MIXING WITHIN
THE BOUNDARY LAYER. THE HIGHER RESOLUTION NAM AND RSM SEEM TO HAVE A
BETTER HANDLE ON THE WINDS THAN THE GFS.
BY MIDWEEK...ATTENTION TURNS TO A DEVELOPING SYSTEM EAST OF THE
STATE. THE SHORTWAVE CURRENTLY NEAR 50N MENTIONED ABOVE WILL DIG
SOUTHEASTWARD AND EVENTUALLY CUTOFF. THIS IS THE SYSTEM THAT THE
EXTENDED MODELS HAVE BEEN HAVING TROUBLE WITH THE PAST FEW DAYS. THE
12Z GFS HAS CONTINUED THE TREND OF ITS RECENT RUNS...DEVELOPING THE
LOW FARTHER EAST AWAY FROM THE STATE. THE 12Z ENSEMBLES STILL SHOW
10-15 DEGREES OF SPREAD LONGITUDINALLY AS TO WHERE THE LOW WILL
DEVELOP...WHICH IS BETTER THAN THE 30-40 DEGREES OF SPREAD FROM
EARLIER RUNS. THE ENSEMBLES BREAK DOWN INTO TWO MAIN GROUPS...A MORE
CUTOFF/MORE WESTERLY ONE WHICH INCLUDES THE OPERATIONAL RUN AND A
MORE PROGRESSIVE/MORE EASTERLY ONE. EITHER WAY...IT PLACES HAWAII
MORE SOLIDLY IS A PERSISTENT NORTHEASTERLY FLOW THAN EARLIER RUNS.
THE 12Z ECMWF ALSO SHOWS THE SAME TREND...DEVELOPING THE CUTOFF LOW
FARTHER EAST AND KEEPING US UNDER STRONGER NORTHEASTERLIES. GIVEN
THE CONSISTENT TREND OF THE EXTENDED MODELS...WITH ADJUST THE
FORECAST TOWARD THIS SOLUTION.
MARINE
THE WAIMEA BAY BUOY HAS BEEN RUNNING 9-10 FEET/17-18 SECONDS THIS
MORNING...WHICH IS STILL A FEW FEET HIGHER THAN THE 12Z WAVEWATCH
III GUIDANCE. OBSERVERS FROM THE NORTH SHORE OF OAHU REPORT SURF OF
UP TO 20 FEET...IN LINE WITH THE GOING HIGH SURF ADVISORY. WW3 SHOWS
THE CURRENT SWELL SLOWLY SUBSIDING ON MONDAY. IN ADDITION...WITH THE
HIGHER SWELL AND HIGHER SIGNIFICANT WAVE HEIGHTS...WE HAVE ISSUED A
SMALL CRAFT ADVISORY FOR 10 FOOT SEAS FOR THE NORTHWEST COASTAL
WATERS THROUGH TONIGHT.
IN ADDITION TO THE SEAS...WINDS WILL INCREASE TO SMALL CRAFT
ADVISORY LEVELS OF 25 KNOTS BEHIND THE COLD FRONT. WINDS WILL BE
STRONGEST AGAIN ACROSS NORTHWEST WATERS...WHERE THE FRONT WILL HAVE
THE MOST STRENGTH. THE MORNING QUIKSCAT PASS SHOWED WINDS OF +25
KNOTS BEHIND THE BOUNDARY...AND 12Z NAM/RSM SHOW WINDS OF THIS
STRENGTH REACHING KAUAI LATE MONDAY.
HFO WATCHES/WARNINGS/ADVISORIES
HIGH SURF ADVISORY FOR NORTH AND WEST FACING SHORES OF NIIHAU KAUAI
AND OAHU UNTIL 6 PM MONDAY.
HIGH SURF ADVISORY FOR NORTH FACING SHORES OF MOLOKAI AND MAUI UNTIL
6 PM MONDAY.
SMALL CRAFT ADVISORY UNTIL 10 PM HST THIS EVENING FOR KAUAI
NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-
KAUAI CHANNEL-OAHU WINDWARD WATERS.
BRAVENDER
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