Image Department Meteorology
Meteorology_Home Weather_Server News/Seminars
People
Research
Academics Application Contact_Us

Hawaiian_Weather
US_Mainland_Weather
Tropical_Weather
Satellite_Imagery
Polar_Imagery
Radar_Imagery
Marine
Numerical_Models
LAPS
Lightning_Data
Forecasts
Vog_Forecasts
Observations
Archive
Links Disclaimer
Space
SOEST_Home
University_of_Hawaii_Home

Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans:
Narrow the Menu List
Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit
Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special
Hawaiian Islands Synoptic Discussion and Guidance

852
FXHW60 PHFO 301334
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
334 AM HST MON MAR 30 2015

.SYNOPSIS...
A FAIRLY WET TRADE WIND WEATHER PATTERN WILL PREVAIL THROUGH MOST
OF THE UPCOMING WEEK. WHILE THE TRADE WINDS WILL FOCUS SHOWERS
OVER WINDWARD SLOPES AND COASTS...LEEWARD AREAS WILL SEE A FEW
SHOWERS AS WELL. LIGHTER WINDS WILL ALLOW SEABREEZES TO DEVELOP
IN SOME AREAS ON TUESDAY...WITH SCATTERED SHOWERS POSSIBLE ACROSS
INTERIOR AND LEEWARD SECTIONS.

&&

.DISCUSSION...
FREQUENT SHOWERS HAVE CONTINUED TO STREAM ACROSS MAINLY WINDWARD
SECTIONS OF THE STATE DURING THE NIGHT. RAINFALL AMOUNTS HAVE BEEN
GENERALLY LIGHT...WITH MOST WINDWARD GAUGES RECORDING LESS THAN A
QUARTER INCH DURING THE PAST SIX HOURS. SURFACE ANALYSIS DEPICTS A
1031 MB HIGH ABOUT 800 MILES NORTH OF KAUAI. MODERATE TO FRESH
TRADES PREVAIL OVER THE STATE TO THE SOUTH OF THIS HIGH. ALOFT...
A FLAT RIDGE AXIS IS BEING GRADUALLY SUPPRESSED SOUTH OF THE
STATE...AS A SHORTWAVE TROUGH PUSHES EASTWARD FROM THE DATELINE
ALONG 30N. THE 12Z SOUNDINGS SHOW SLIGHTLY WEAKENED INVERSIONS
BASED AROUND 8000 FEET...WITH NEAR NORMAL PWATS JUST OVER ONE
INCH. MIMIC-TPW SATELLITE IMAGERY INDICATES A SLIGHTLY DRIER AIRMASS
JUST TO THE EAST OF THE STATE...WITH ESTIMATED PWATS IN THAT AREA
SLIGHTLY BELOW ONE INCH.

MODERATE TO FRESH TRADES WILL CONTINUE ACROSS THE STATE TODAY...
AS THE SFC HIGH PASSES BY TO OUR NORTH. HEIGHTS WILL BEGIN TO FALL
ALOFT...AS A MID/UPPER LEVEL TROUGH PUSHES EASTWARD FROM THE
DATELINE OVER THE NW HAWAIIAN ISLANDS. THIS WILL ALLOW FOR THE
INVERSION TO RISE AND WEAKEN FURTHER...CONTINUING THE PROCESS
WHICH APPEARS TO HAVE ALREADY BEGUN DURING THE NIGHT. THIS SHOULD
KEEP TRADE WIND SHOWERS FAIRLY ACTIVE EVEN DURING THE AFTERNOON
HOURS...ALTHOUGH THE SLIGHTLY DRIER AIRMASS MOVING IN FROM THE
EAST MAY REDUCE SHOWER COVERAGE SOMEWHAT.

TRADES ARE EXPECTED TO WEAKEN TONIGHT AND TUESDAY...AS THE
MID/UPPER TROUGH PASSES NORTH OF THE STATE...AND A WEAK SFC TROUGH
DEVELOPS IN RESPONSE NEAR AND NORTH OF THE ISLANDS. MODELS
INDICATE THAT THE INVERSION WILL WEAKEN AND RISE A BIT FURTHER
DURING THIS TIME...WITH SOME MODEST INCREASE OF LOW LEVEL MOISTURE
AS WELL. THE TRADES MAY WEAKEN ENOUGH TO ALLOW SEABREEZES TO
DEVELOP ACROSS MANY AREAS ON TUESDAY AFTERNOON. INCREASED
MOISTURE/INSTABILITY COULD GENERATE A FEW HEAVIER DOWNPOURS MONDAY
NIGHT AND TUESDAY...POTENTIALLY ALSO ENHANCED BY SEABREEZE
CONVERGENCE TUESDAY AFTERNOON.

TRADE WINDS SHOULD INCREASE OVER THE ISLANDS ONCE AGAIN ON
WEDNESDAY AS THE MID LEVEL DISTURBANCE MOVES AWAY TO OUR NE AND
THE NEARBY LOW LEVEL TROUGH WASHES OUT. A SHORTWAVE MID LEVEL
RIDGE PASSING OVERHEAD SHOULD STRENGTHEN AND LOWER THE INVERSION
ONCE AGAIN AS WELL...THUS WOULD EXPECT TYPICAL TRADE WIND WEATHER
WITH MOSTLY LIGHT SHOWERS FOCUSING WINDWARD AND MAUKA.

FORECAST UNCERTAINTY INCREASES FROM THURSDAY INTO NEXT WEEKEND...
DUE TO MODEL VARIATIONS IN THE EVOLUTION OF A COMPLEX DEEP LAYERED
TROUGH DEVELOPING OVER THE CENTRAL PACIFIC. MOST OF THE MODELS VEER
AND WEAKEN TRADE WIND FLOW LOCALLY TO SOME EXTENT...WITH THE
SMALLER ISLANDS POSSIBLY FALLING WITHIN THE RAIN SHADOW OF THE
BIG ISLAND. AS NOTED PREVIOUSLY...A 10-20 DEGREE DIFFERENCE IN
WIND DIRECTION WOULD HAVE SIGNIFICANT IMPLICATIONS FOR SENSIBLE
WEATHER OVER THE ISLANDS DURING THIS TIME. FORECAST MODELS HAVE
BEEN INCONSISTENT WITH THEIR SOLUTIONS FOR EARLY THIS WEEK...
THEREFORE CONFIDENCE IN THE LATER PERIOD FORECASTS IS NOT
PARTICULARLY HIGH AT THIS TIME.

&&

.AVIATION...
CLOUDS AND SHOWERS WILL REMAIN FOCUSED OVER WINDWARD SECTIONS OF
THE STATE TODAY...AS MODERATE TO FRESH TRADE WINDS PREVAIL. AIRMET
SIERRA FOR MOUNTAIN OBSCURATION REMAINS IN EFFECT FOR WINDWARD
SECTIONS OF ALL ISLANDS.

VFR CONDITIONS WILL PREVAIL ELSEWHERE...WITH JUST ISOLATED MVFR
CEILINGS POSSIBLE AT TIMES MAINLY IN -SHRA.

AIRMET TANGO FOR MODERATE LOW LEVEL TURBULENCE IS IN EFFECT
OVER AND S THRU W OF THE MOUNTAINS DUE TO THE TRADE WINDS.

&&

.MARINE...
NW SWELL PEAKED AROUND MIDDAY SUNDAY AT BUOY 51101...AND APPEARS
TO HAVE PEAKED DURING THE NIGHT AT THE NEARSHORE CDIP BUOYS OFF
KAUAI AND OAHU. THIS SWELL AND RESULTING SURF WILL CONTINUE
TO GRADUALLY SUBSIDE TODAY THROUGH TUESDAY...AND THE HIGH SURF
ADVISORY FOR NORTH AND WEST FACING SHORES HAS BEEN DROPPED.

OTHERWISE...SMALL SOUTH SWELL WILL CONTINUE PRODUCING SMALL SURF
ON SOUTH FACING SHORES THROUGH MID WEEK. A SMALL WNW SWELL MAY
ARRIVE INTO THE ISLANDS NEXT WEEKEND.

THE SUNDAY EVENING ASCAT PASS MISSED THE HAWAIIAN COASTAL WATERS...
BUT AVAILABLE MESONET DATA AND HIGH-RESOLUTION WRF MODEL OUTPUT
SUGGEST THAT SMALL CRAFT ADVISORY WINDS OF 25 KT ARE CONTINUING
IN THE TYPICALLY WINDY WATERS AROUND THE BIG ISLAND AND MAUI
COUNTY. THE ADVISORY REMAINS POSTED FOR THOSE AREAS THROUGH
TODAY. MODELS SUGGEST THAT 25 KT WINDS MAY PERSIST ACROSS SOME
WATERS INTO TONIGHT...BUT WILL LET THE DAY SHIFT MONITOR LATER
TRENDS AND HOPEFULLY SEE AN ASCAT PASS BEFORE DECIDING WHETHER TO
EXTEND THE SCA BEYOND 6 PM.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

$$

JACOBSON





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



This page is maintained voluntarily by the MKWC and the UHMET faculty, staff, and students.
It was last modified on: Tue, Sep 21 2010 - 2314 UTC
Send comments to: Ryan Lyman