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Hawaiian Islands Synoptic Discussion and Guidance
503
FXHW60 PHFO 230134
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST SUN NOV 22 2009
.SYNOPSIS...
HIGH PRESSURE TO THE NORTHEAST OF THE ISLANDS IS MOVING EAST AND THE
ASSOCIATED SURFACE RIDGE WILL MOVE NEARER TO THE ISLANDS. TRADE
WINDS WILL BE MODERATE IN STRENGTH AND THEN INCREASE AGAIN WEDNESDAY
WHEN A NEW HIGH BUILDS TO THE NORTH. PASSING SHOWERS WILL MAINLY
AFFECT THE WINDWARD OR MOUNTAIN AREAS.
&&
.DISCUSSION...
PRECIPITATION THROUGH THE DAY HAS BEEN SPARSE...MOSTLY CONFINED TO
THE WINDWARD BIG ISLAND. SATELLITE IMAGERY SHOWS SOME SHOWER CLOUDS
UPWIND...WHICH IS TO THE EAST NORTHEAST OF THE MAIN HAWAIIAN
ISLANDS...THAT MAY COME ASHORE LATER TONIGHT. THE SHOWERS WOULD BE
LESS SIGNIFICANT THAN LAST NIGHT. AFTERNOON BALLOON SOUNDINGS ARE
STABLE AND RELATIVELY DRY.
&&
.PREV DISCUSSION 10 AM...
OVERALL THROUGH MOST OF THIS WEEK A STANDARD WEATHER
PATTERN WILL PREVAIL IN WHICH TRADE WIND SHOWERS FAVOR THE WINDWARD
AND MOUNTAIN AREAS. SHOWER ACTIVITY IS TYPICALLY SOMEWHAT GREATER
DURING THE NIGHTTIME AND MORNING HOURS. THE ATMOSPHERE IS QUITE DRY
THROUGH MID AND UPPER LEVELS DUE TO THE RIDGING ALOFT. GFS AND ECMWF
MODELS SHOW SOME MOISTURE BEING DRAWN UP FROM THE SOUTHEAST ONTO THE
BIG ISLAND WEDNESDAY AND THURSDAY...THIS MOISTURE COULD BE ADVECTED
INTO THE TRADE WIND FLOW AND LEAD TO ENHANCED TRADE SHOWERS OVER THE
SMALLER ISLANDS BY MID WEEK.
OVER THE NORTH PACIFIC...THE SURFACE HIGH FAR NORTHEAST WILL SHIFT
EASTWARD AND THE SURFACE RIDGE WILL MOVE TO ALMOST 200 MILES NORTH
OF HONOLULU MONDAY AND TUESDAY. TRADE WINDS WILL DECREASE TO
MODERATE STRENGTH DURING THIS PERIOD. MODELS AGREE ON MOVING A COLD
FRONT TOWARD KAUAI TUESDAY NIGHT BUT STALLING IT NORTH OF THE
ISLANDS WEDNESDAY AND THURSDAY. IT APPEARS THE ASSOCIATED UPPER
TROUGH IS NOT STRONG ENOUGH TO PUSH THE FRONT DOWN ACROSS THE MAIN
HAWAIIAN ISLANDS. BY WEDNESDAY A NEW SURFACE HIGH MOVES IN BEHIND
THE FRONT AND TRADE WINDS ARE STRENGTHENED.
&&
.MARINE...
THE CURRENT HIGH SURF ADVISORY FOR NORTH AND WEST KAUAI AND
NIIHAU...AS WELL AS NORTH SHORES OF OAHU MOLOKAI AND MAUI RUNS
THROUGH MONDAY NIGHT. IT IS POSSIBLE THE ADVISORY MAY BE EXTENDED
THROUGH TUESDAY. SURF WILL BE RUNNING HIGH ON NORTHERN AND SOME
WESTERN SHORES MOST DAYS THIS WEEK DUE TO A SUCCESSION OF STRONG
LOWS MOVING ACROSS THE NORTH PACIFIC. A LARGE STORM SYSTEM THAT
MOVED INTO THE CENTRAL NORTH PACIFIC TODAY SHOULD PRODUCE A LARGER
NORTHWEST SWELL THAT WOULD ARRIVE TUESDAY NIGHT WITH THE PEAK
OCCURRING WEDNESDAY. WARNING LEVEL SURF REACHING 25 FEET ON
WEDNESDAY IS LIKELY ON NORTH FACING SHORES THAT HAVE GOOD EXPOSURE
TO THIS NEXT NORTHWEST SWELL.
SMALL CRAFT ADVISORIES HAVE BEEN CANCELED. THE TYPICALLY WINDY
CHANNELS AND WATERS SOUTH OF THE BIG ISLAND WILL LIKELY BE AT SMALL
CRAFT ADVISORY STRENGTH AGAIN BY TUESDAY NIGHT OR WEDNESDAY WHEN
TRADE WINDS INCREASE.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST TUESDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU-MOLOKAI-MAUI
WINDWARD WEST-WINDWARD HALEAKALA.
&&
$$
HOAG
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
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This page is maintained voluntarily by the MKWC and the UHMET faculty, staff, and students.
It was last modified on: Tue, Jun 16 2009 - 0632 UTC
Send comments to: Ryan Lyman
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