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Hawaiian Islands Synoptic Discussion and Guidance

520
FXHW60 PHFO 241701 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
701 AM HST MON NOV 24 2014

.UPDATE...
ADJUSTED CHANCES FOR RAIN TODAY AS A COLD FRONT PROGRESSES
EASTWARD ACROSS THE ISLAND CHAIN. INCREASED POPS OVER OAHU UNTIL
MID-MORNING...THEN BEGINNING OVER MAUI COUNTY MID-MORNING AND BIG
ISLAND THIS AFTERNOON.

&&

.SYNOPSIS...
A WEAKENING COLD FRONT WILL CONTINUE TO MOVE ACROSS THE SMALLER
ISLANDS THIS MORNING...THEN STALL AND QUICKLY DISSIPATE NEAR THE
BIG ISLAND LATER THIS AFTERNOON. SHOWERS WILL BRING MAINLY LIGHT TO
MODERATE RAIN...BUT A FEW BRIEF PERIODS OF LOCALIZED HEAVY RAIN ARE
CERTAINLY POSSIBLE...ESPECIALLY OVER MOUNTAIN AREAS OF OAHU AND MAUI
COUNTY. COOLER...DRIER AIR AND STRONGER NORTHERLY WINDS WILL FOLLOW
THE FRONT...WITH WINDS TURNING NORTH LATER THIS AFTERNOON AND
NORTHEAST BY TUESDAY. LOCALLY BREEZY TRADES WILL THEN CONTINUE
THROUGH THE WEEK...BRINGING BRIEF WINDWARD AND MAUKA SHOWERS.

&&

.PREV DISCUSSION.../ISSUED 410 AM HST MON NOV 24 2014/

A SHARP MID/UPPER LVL TROUGH CONTINUES TO MIGRATE E AT ABOUT 30 MPH
ACROSS THE N CENTRAL PACIFIC...WHILE A SFC COLD FRONT BOUNDARY
MOVING ACROSS THE CENTRAL PART OF THE ISLAND CHAIN. A BAND OF
SHOWERS WITH PERIODS OF BRIEF LOCALIZED HEAVY RAIN MARKS THE
LEADING EDGE OF THE FRONT...WHICH WAS OBSERVED ON RADAR OVER OAHU
AT AROUND 700 AM HST. THE BAND OF SHOWERS IS MOVING E/SE AT 20 TO
25 MPH...AND RAIN COVERAGE SHOULD GRADUALLY DECREASE ACROSS OAHU
BY MID-MORNING. RAIN IS EXPECTED TO STAY OVER OAHU UNTIL MID-
MORNING...THEN MOVE OVER MAUI COUNTY BY MID-MORNING AND BIG ISLAND
BY THIS AFTERNOON. MODERATE RAIN AND BRIEF HEAVY DOWNPOURS WILL BE
POSSIBLE ALONG THE FRONT.

MEANWHILE...SFC HIGH PRESSURE REMAINS CENTERED FAR NE OF THE
AREA...WITH AN ASSOCIATED SFC RIDGE AXIS STRETCHING TO ABOUT 200
MILES SE OF THE BIG ISLAND. THIS SYNOPTIC SETUP IS NOW SHIFTING
WINDS AROUND THE BIG ISLAND TO A MORE S TO SW FLOW AS THE FRONT
CONTINUES TO MOVE DOWN THE ISLAND CHAIN TODAY. THE BULK OF THE MODEL
GUIDANCE REMAINS IN FAIR AGREEMENT REGARDING THE OVERALL SOLUTION
FOR THE FROPA...MOVING ACROSS OAHU AND MAUI COUNTY THROUGH THE REST
OF THE MORNING HOURS...THEN STALLING AND QUICKLY BREAKING DOWN
AROUND THE BIG ISLAND THIS AFTERNOON. A RELATIVELY DRY PROFILE FOR
THE MID LVLS...AND PWATS AROUND 1 INCH IN THE 12Z LIHUE SOUNDING
SUGGEST THAT SHOWERS SHOULD REMAIN LIGHT TO MODERATE IN GENERAL.

AN UPPER LEVEL TROUGH IS PASSING NORTH OF HAWAII TODAY CAUSING
STRONG WINDS ALOFT OVER THE STATE. WINDS AT THE SUMMITS OF MAUNA
KEA AND MAUNA LOA ARE EXPECTED IN THE ADVISORY LEVEL RANGE
TODAY...WESTERLY AT 35 TO 50 MPH AND GUSTS TO 60 MPH.

AS THE FRONT DISSIPATES AND HIGH PRESSURE RE-ESTABLISHES IN THE WAKE
OF THE AFOREMENTIONED UPPER LEVEL TROUGH...WINDS BEHIND THE FROPA
WILL STRENGTHEN AND TURN FROM THE N THIS LATER THIS AFTERNOON.
OVERALL CONDITIONS WILL BECOME MUCH DRIER AND GUSTY LATE TONIGHT
THROUGH TUE...WITH DEWPOINTS DROPPING INTO THE UPPER 50S.

THE STRONG HIGH PRESSURE N OF THE ISLANDS WILL KEEP A MODERATE TO
LOCALLY FRESH TRADE WIND REGIME ACROSS THE AREA THROUGH THE REST OF
THE WEEK. LOW LEVEL MOISTURE SHOULD GRADUALLY RECOVER DURING THE
SECOND HALF OF THE WEEK WITH SHOWER ACTIVITY SHIFTING OVER WINDWARD
AND MAUKA AREAS.


&&

.AVIATION...
A COLD FRONT MOVING ACROSS OAHU AS OS 17Z WILL CONTINUE MOVING
SOUTHEAST ACROSS THE STATE TODAY...REACHING MOLOKAI AND MAUI COUNTY
LATER THIS MORNING. AREAS OF MVFR CONDITIONS WILL BE LIKELY
WITHIN A BAND OF CLOUDS AND SHOWERS ALONG THE FRONT...WITH
ISOLATED/BRIEF IFR CONDITIONS POSSIBLE. AIRMET SIERRA FOR MOUNTAIN
OBSCURATION HAS BEEN POSTED ACROSS OAHU THROUGH 19Z AND MAYBE COME
NECESSARY FOR MAUI COUNTY LATER. THE FRONT WILL
WEAKEN AS IT APPROACHES THE BIG ISLAND LATE THIS AFTERNOON INTO
THIS EVENING...BUT DEVELOPING NORTHERLY FLOW WILL LIKELY CAUSE AN
INCREASE IN SHOWER ACTIVITY AND THE POTENTIAL FOR MOUNTAIN
OBSCURATION ALONG THE SLOPES OF THE HAMAKUA COAST.

A TROUGH ALOFT WILL ALSO BE PASSING ACROSS THE STATE TODAY. MODELS
INDICATE SOME POTENTIAL FOR HIGH LEVEL TURBULENCE AS THIS TROUGH
MOVES THROUGH...BUT GIVEN THE LACK OF ANY TURB REPORTS FROM
AIRCRAFT TRANSITING BETWEEN HAWAII AND ASIA HAVE ONLY INCLUDED A
MENTION OF ISOLATED MOD TURB IN THE AIRMET TANGO BULLETIN AT THIS
TIME.

&&

.MARINE...
THE COMBINATION OF STRONG NORTHERLY WINDS BEHIND A COLD FRONT AND A
LARGE NORTHWEST SWELL WILL BRING SMALL CRAFT ADVISORY CONDITIONS
OVER MOST MARINE ZONES THROUGH 6 AM HST TUESDAY. THEN BY WEDNESDAY...
STRONG NORTHEASTERLY WINDS WILL LIKELY BRING ANOTHER ROUND OF SMALL
CRAFT ADVISORY CONDITIONS OVER THE TYPICALLY WINDIER WATERS AROUND
THE BIG ISLAND AND MAUI COUNTY.

THE CURRENT NORTH-NORTHWEST SWELL WILL BRING SURF HEIGHTS TO
ADVISORY THROUGH TUESDAY FOR NORTH FACING SHORES OF ALL SMALLER
ISLANDS...AND FOR WEST FACING SHORES OF KAUAI COUNTY. BREEZY TRADE
WINDS LATER IN THE WEEK WILL PRODUCE CHOPPY SURF ALONG EAST FACING
SHORES...BUT IS EXPECTED TO REMAIN BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU-MOLOKAI-MAUI
WINDWARD WEST-WINDWARD HALEAKALA.

WIND ADVISORY UNTIL 6 PM HST THIS EVENING FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-KAIWI CHANNEL-MAUI
COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND WINDWARD WATERS.

SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM HST TUESDAY
FOR BIG ISLAND SOUTHEAST WATERS.

&&

$$

UPDATE...FOSTER
DISCUSSION/MARINE...FOSTER/REYNES
AVIATION...EATON




Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office