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Hawaiian Islands Synoptic Discussion and Guidance

910
FXHW60 PHFO 292007
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1007 AM HST THU JAN 29 2015

.SYNOPSIS...
CLOUDS AND A FEW SHOWERS ASSOCIATED WITH A WEAK FRONT WILL MOVE OVER
KAUAI AND OAHU TODAY...AND GRADUALLY SPREAD TO MAUI COUNTY TONIGHT
AND FRIDAY. THIS MOISTURE WILL LINGER THROUGH THE WEEKEND...AND A
BRIEF RETURN OF LIGHT TRADE WINDS WILL FOCUS PASSING SHOWERS OVER
WINDWARD SLOPES... WITH AFTERNOON CLOUDS OVER LEEWARD AREAS.
WINDS WILL TURN SOUTH MONDAY AND THEN WEST THROUGH MIDWEEK WITH
AN INCREASE IN SHOWERS.

&&

.DISCUSSION...
A DIFFUSE COLD FRONT PASSING THROUGH THE ISLANDS IS BRINGING A BANDS OF
LOW OVERCAST CLOUDS TO THE AREA. THIS MORNING... OAHU IS CURRENTLY
UNDER ONE OF THESE CLOUD BANDS WITH CLOUDY SKIES PREVAILING AND
LIGHT TO MODERATE SHOWERS MOVING INTO THE ISLAND FROM THE
SOUTHWEST. THESE CLOUDS AND SHOWERS ARE EXPECTED TO DIMINISH OVER
OAHU THIS AFTERNOON. KAUAI IS IN A DRY SLOT BETWEEN CLOUD BANDS
BUT LOW CLOUDS ARE EXPECTED TO OVERTAKE THE GARDEN ISLE THIS
AFTERNOON WITH SCATTERED SHOWERS. ISLANDS FROM MAUI TO THE BIG
ISLAND HAVE RELATIVELY CLEAR SKIES WITH LIGHT SOUTHEAST FLOW.
CLOUDS WILL FILL IN OVER THE LOWER ELEVATIONS OF MAUI AND COUNTY
AND THE BIG ISLAND AS DAYTIME HEATING PROGRESSES. TONIGHT... SOME
FRONTAL MOISTURE WILL REACH MAUI COUNTY BRINGING AN INCREASE TO
CLOUDS AND CHANCE OF SHOWERS OVER LEEWARD SLOPES.

WINDS WILL REMAIN LIGHT THROUGH THE WEEKEND BUT WIND DIRECTION
WILL SPIN AROUND THE COMPASS AS THE GENERAL FLOW SHIFTS FROM SW
TODAY... WEST OVERNIGHT... NORTH FRIDAY... NE SATURDAY... EAST
SUNDAY... AND FINALLY BACK TO SOUTH MONDAY. THE WEAK FRONT NEAR
THE ISLANDS TODAY WILL PULL NORTH OVERNIGHT WITH A WEAK RIDGE
FILLING IN NORTH OF THE ISLANDS OVER THE WEEKEND. MOISTURE FROM
THE FRONT WILL LINGER OVER WINDWARD AREAS BRINGING PASSING CLOUDS
AND LIGHT/MODERATE SHOWERS THROUGH THE WEEKEND. FOR LEEWARD AREAS
OVER THE WEEKEND... AFTERNOON CLOUDS AND SEA BREEZES ARE LIKELY
WITH THE SEA BREEZES OVERPOWERING THE LIGHT TRADES. NIGHTTIME
SKIES WILL CLEAR WITH COOLER LATE NIGHT TEMPERATURES DUE TO
RADIATIONAL HEATING.

A FRONT APPROACHING FROM THE NORTHWEST WILL TURN ISLAND WINDS OUT
OF THE SOUTH MONDAY INTO MONDAY NIGHT WHILE PUSHING THE SURFACE
RIDGE SOUTH OF THE ISLANDS. SHOWER COVERAGE WILL INCREASE WITH THE
ISLAND TOPOGRAPHY FOCUSING RAINFALL OVER THE LEEWARD SLOPES.
TUESDAY/WEDNESDAY WINDS SHIFT FROM THE WEST WITH WEST FACING
SLOPES CATCHING THE MAJORITY OF RAINFALL AND SCATTERED SHOWERS
FALLING ELSEWHERE. THESE WEST WINDS WILL USHER THE INITIAL FRONT
OVER THE ISLANDS TUESDAY...WITH ANOTHER EXPECTED THURSDAY. THE
FRONTS WILL BE A FOCUS OF RAINFALL AS THEY MOVE OVER THE STATE.
WINDS OVER THE BIG ISLAND SUMMITS ARE ALSO EXPECTED TO INCREASE
AROUND THIS TIME. THE GFS AND ECMWF DIFFER ON THE TIMING AND
STRENGTH OF THESE FRONTS...THUS THE LONGER RANGE FORECAST WILL
POTENTIALLY BE SUBJECT TO LARGE CHANGES.

&&

.AVIATION...
A WEAK FRONT JUST NW OF KAUAI...WILL MOVE THROUGH KAUAI THIS
AFTERNOON...PASS OVER OAHU THIS EVENING AND MOVE INTO MAUI COUNTY
OVERNIGHT. PREDOMINANTLY VFR CONDITIONS ARE EXPECTED AT THE
TERMINALS...BUT BRIEF PERIODS OF MVFR CIGS AND -SHRA WILL BE
POSSIBLE ALONG AND AHEAD OF THIS FRONT.

AIRMET SIERRA IS CURRENTLY IN EFFECT FOR MTN OBSC OVER OAHU. WE MAY
BE ABLE TO DROP THE AIRMET FOR AWHILE THIS AFTERNOON...BUT MTN OBSC
MAY BECOME A PROBLEM AGAIN THIS EVENING AS THE FRONT APPROACHES.
AIRMETS FOR MTN OBSC MAY BE ALSO BE NEEDED FOR KAUAI THIS AFTERNOON
AS THE FRONT MOVES THROUGH.

&&

.MARINE...
A MODERATE NW SWELL WILL GRADUALLY DIMINISH THROUGH TONIGHT.
HOWEVER... REINFORCING SWELLS FROM THE NW AND NNW WILL ARRIVE
FRIDAY AND SATURDAY RESPECTIVELY...LEADING TO ELEVATED SURF ALONG
N FACING SHORES...AND LESS SO ALONG W FACING SHORES...ESPECIALLY
AS THE SWELL TURNS TOWARD THE N SATURDAY. BOTH SWELLS WILL
PRODUCE SURF NEAR ADVISORY LEVELS...WITH SURF REMAINING ELEVATED
THROUGH SUNDAY BEFORE GRADUALLY DIMINISHING MONDAY AND TUESDAY.
THE OAHU SURF DISCUSSION /SRDHFO/ WAS UPDATED WEDNESDAY AND
CONTAINS DETAILED INSIGHT ON THE SOURCE OF THE SWELLS.

WHILE WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY /SCA/
CRITERIA THROUGH AT LEAST THE WEEKEND...COMBINED SEAS MAY TOP OUT
NEAR 10 FEET SATURDAY IN MARINE ZONES EXPOSED TO THE NNW SWELL.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

MORRISON...DISCUSSION AND MARINE
JELSEMA...AVIATION



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