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Hawaiian Islands Synoptic Discussion and Guidance

917
FXHW60 PHFO 300135
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
335 PM HST THU JAN 29 2015

.SYNOPSIS...
CLOUDS AND A FEW SHOWERS ASSOCIATED WITH A WEAK FRONT WILL LINGER
OVER THE SMALLER ISLANDS THROUGH FRIDAY. FOR THE WEEKEND... A
BRIEF RETURN OF LIGHT TRADE WINDS WILL FOCUS PASSING SHOWERS OVER
WINDWARD SLOPES... WITH AFTERNOON SEA BREEZES AND CLOUDS OVER
LEEWARD AREAS. WINDS WILL TURN SOUTH MONDAY AND THEN WEST THROUGH
MIDWEEK WITH INCREASING SHOWERS.

&&

.DISCUSSION...

A DIFFUSE FRONT NEAR THE ISLANDS IS BRINGING BANDS OF LOW OVERCAST
CLOUDS THIS AFTERNOON TO OAHU AND KAUAI. TONIGHT... SOME FRONTAL
MOISTURE WILL REACH MAUI COUNTY BRINGING AN INCREASE TO CLOUDS AND
CHANCE OF SHOWERS OVER LEEWARD SLOPES... WHILE PASSING SHOWERS AND
PARTLY CLOUDY SKIES REMAIN OVER OAHU AND KAUAI. THE BIG ISLAND
WILL SEE PARTIAL CLEARING TONIGHT AS LAND BREEZES PUSH CLOUDS AND
MOISTURE OFFSHORE.

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...
BRIEF PERIODS OF MVFR CIGS AND -SHRA WILL BE POSSIBLE IN ASSOCIATION
WITH A WEAKENING FRONTAL BOUNDARY...PARTICULARLY ACROSS MAUI COUNTY
LATE TONIGHT THROUGH MID MORNING FRIDAY. OTHERWISE...PREDOMINANTLY
VFR CONDITIONS ARE EXPECTED AT THE TERMINALS THROUGH THE TAF
FORECAST PERIOD.

AIRMET SIERRA REMAINS IN EFFECT FOR MTN OBSC OVER OAHU. CONDITIONS
ARE EXPECTED TO IMPROVE BY 0400Z...AND THE AIRMET WILL LIKELY BE
CANCELLED AT THAT TIME.

MTN OBSC HAS ENDED OVER KAUAI...SO THE AIRMET HAS BEEN CANCELLED
HERE.

ADDITIONAL AIRMETS FOR MTN OBSC MAY BE NEEDED LATER TONIGHT FOR MAUI
COUNTY.

&&

.MARINE...
A MODERATE NW SWELL WILL GRADUALLY DIMINISH THROUGH TONIGHT.
HOWEVER... REINFORCING SWELLS FROM THE NW AND NNW WILL ARRIVE
FRIDAY AND SATURDAY RESPECTIVELY...CONTINUING ELEVATED SURF
THROUGH THE WEEKEND ALONG N FACING SHORES...AND LESS SO ALONG W
FACING SHORES...ESPECIALLY AS THE SWELL TURNS TOWARD THE N
SATURDAY. SURF WILL GRADUALLY DIMINISH 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