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Hawaiian Islands Synoptic Discussion and Guidance

859
FXHW60 PHFO 270146
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST SUN APR 26 2015

.SYNOPSIS...
A WEAKENING FRONT WILL MOVE ACROSS OAHU THIS EVENING...REACH MAUI
COUNTY OVERNIGHT...THEN DISSIPATE OVER MAUI COUNTY MONDAY NIGHT AND
TUESDAY. SOME PASSING SHOWERS WILL ACCOMPANY THE FRONT. HIGH
PRESSURE WILL BUILD IN NORTH OF THE AREA THIS WEEK WITH TRADE WINDS
BECOMING RATHER BREEZY. ABUNDANT CLOUD COVERAGE AND OCCASIONAL
SHOWERS WILL OCCUR OVER WINDWARD AND MAUKA AREAS WITH THE TRADE
WINDS SUFFICIENTLY STRONG TO BLOW SOME PASSING SHOWERS OVER TO SOME
LEEWARD LOCATIONS.

&&

.DISCUSSION...
THE LEADING EDGE OF A WEAKENING FRONTAL BAND HAS RECENTLY REACHED
NORTHERN AND WESTERN SECTIONS OF OAHU WITH THE BACK EDGE IN THE
KAUAI CHANNEL. RADAR AND SATELLITE IMAGERY SHOWS THE FRONT IS MOVING
VERY SLOWLY TOWARD THE EAST AT THE PRESENT TIME. UPPER LEVEL SUPPORT
IS LACKING IN THE ISLAND VICINITY SO MAINLY LIGHT SHOWERS ARE
ACCOMPANYING THE FRONT WITH A FEW EMBEDDED MODERATE SHOWERS EMBEDDED
ALONG IT. THERE ARE ALSO A FEW PASSING SHOWERS SEEN OUT AHEAD OF THE
FRONT. THE FRONT WILL CONTINUE MOVE OVER OAHU THIS EVENING
ACCOMPANIED BY SOME PASSING SHOWERS. THE FRONT WILL THEN SPREAD
OVER MAUI COUNTY LATER TONIGHT AND MONDAY WITH MAINLY LIGHT SHOWERS
ACCOMPANYING IT. IT IS THEN FORECAST TO DISSIPATE NEAR MAUI MONDAY
NIGHT AND TUESDAY.





STRONG HIGH PRESSURE WILL BE BUILDING IN TO OUR NORTH IN THE FRONTS
WAKE. TRADE WINDS WILL PICK UP AND BECOME RATHER BREEZY FOR MOST OF
THIS WEEK. LEFTOVER MOISTURE FROM THE DISSIPATED FRONT WILL LINGER
ACROSS THE AREA AND OVER THE WATERS TO OUR EAST. ALSO THE WESTERN
END OF A MID LEVEL TROUGH WILL LINGER NEAR THE BIG ISLAND. THE
COMBINATION OF THE STRONGER TRADE WINDS AND ABUNDANT LOW LEVEL
MOISTURE WILL CAUSE A WET TRADE WIND WEATHER PATTERN TO SET UP FOR
THE NEXT FEW DAYS. WINDWARD AND MAUKA AREAS WILL EXPERIENCE THE
GREATEST AMOUNT OF SHOWER ACTIVITY BUT THE TRADE WINDS WILL BE
SUFFICIENTLY STRONG ENOUGH TO BLOW SOME PASSING SHOWERS OVER TO
LEEWARD AREAS AT TIMES.

AS THE HIGH MOVES OFF TO THE NORTHEAST AND WEAKENS LATER IN THE
WEEK...TRADE WINDS WILL GRADUALLY DROP OFF JUST A BIT WITH A DRYING
TREND EXPECTED AS WELL.

&&

.MARINE...
A NEW NORTHERLY SWELL GRADUALLY RISE TONIGHT AND MONDAY WITH SURF
HEIGHTS EXPECTED TO REACH LOW END ADVISORY LEVELS ALONG NORTH AND
EAST FACING SHORELINES. THIS SWELL WILL LINGER ON INTO TUESDAY AND
LOWER GRADUALLY ON WEDNESDAY. STRENGTHENING TRADE WINDS WILL KEEP
SHORT PERIOD CHOPPY SURF ELEVATED ALONG EAST FACING SHORES THROUGH
MOST OF THE WEEK.

STRONG HIGH PRESSURE BUILDING IN TO THE NORTH WILL CAUSE AN INCREASE
IN TRADE WINDS OVER THE AREA THROUGH MOST OF THE WEEK. WINDS AND
SEAS WILL EXCEED SMALL CRAFT ADVISORY THRESHOLDS ACROSS MOST OF THE
AREA BY MONDAY MORNING.

&&

.AVIATION...
A COLD FRONT WILL EDGE SLOWLY SOUTHEASTWARD THROUGH THE ISLAND CHAIN
TONIGHT...PUSHING THROUGH OAHU THIS EVENING AND MOVING INTO MAUI
COUNTY OVERNIGHT. UNSETTLED WEATHER CAN BE EXPECTED AS THE FRONT
MOVES THROUGH WITH OCCASIONAL MVFR CIGS/VSBYS AT THE TAF
SITES...WITH ISOLATED IFR CONDITIONS POSSIBLE. BEHIND THE COLD FRONT
WINDS WILL PICK UP OUT OF THE NORTH AND NORTHEAST AS THE TRADES KICK
BACK IN.

NO AIRMETS ARE CURRENTLY IN EFFECT. AIRMET SIERRA MAY BE NECESSARY
FOR MOUNTAIN OBSCURATION ACROSS OAHU AND MAUI COUNTY LATER THIS
EVENING.

AIRMET TANGO MAY BECOME NECESSARY LATER TONIGHT ACROSS THE NORTHERN
ISLANDS DUE TO MODERATE LOW LEVEL TURB AS THE TRADE WINDS PICK UP
AND INVERSION HEIGHTS LOWER.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM 6 AM MONDAY TO 6 PM HST TUESDAY FOR
NIIHAU-KAUAI WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU-
OLOMANA-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-WINDWARD
HALEAKALA.

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-MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA
CHANNEL.

&&

$$

SYNOPSIS/DISCUSSION/MARINE...BURKE
AVIATION...JELSEMA




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