Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 201355
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
355 AM HST SUN APR 20 2014

.SYNOPSIS...
TRADE WINDS WILL INCREASE TODAY AND TONIGHT...THEN REMAIN STRONG
ON MONDAY...BEFORE DROPPING BACK TO MODERATE LEVELS BY MIDWEEK.
SHOWERS WILL CONTINUE TO FOCUS ACROSS WINDWARD AND MAUKA
AREAS...WITH SHOWERS SPILLING OVER INTO SOME LEEWARD AREAS AS
WELL.

&&

.DISCUSSION...
RADAR LOOPS INDICATE INCREASED SHOWER ACTIVITY MOVING QUICKLY
WESTWARD ACROSS THE STATE DURING THE PAST FEW HOURS...BUT RAIN
GAUGES SHOW GENERALLY LIGHT ACCUMULATIONS OVER WINDWARD AREAS.
THE 12Z SOUNDINGS SHOW THE INVERSION BASED BETWEEN 5500 AND
8000 FEET...WITH WINDS AROUND 850 MB (JUST BELOW THE INVERSION)
INCREASING TO 23-27 KNOTS AT LIHUE. SATELLITE IMAGERY CONTINUES
TO SHOW ABUNDANT MID/HIGH LEVEL CLOUDINESS STREAMING NORTHWARD
ACROSS THE REGION...TO THE EAST OF A MID/UPPER LEVEL TROUGH
CENTERED SEVERAL HUNDRED MILES TO THE SOUTHWEST. AT THE
SURFACE...A 1031 MB HIGH IS CENTERED ABOUT 950 MILES NORTH OF
KAUAI AND IS BUILDING EASTWARD.

THE PRIMARY WEATHER CONCERN THROUGH THE SHORT TERM IS THE
POTENTIAL FOR GUSTY ADVISORY LEVEL TRADE WINDS...AS STRONG HIGH
PRESSURE PASSES BY TO THE NORTH OF THE STATE. THE 00Z UH-WRF RUN
CONTINUES TO SUGGEST THAT THE STRONGEST WINDS ARE LIKELY TO OCCUR
TONIGHT AND MONDAY...WITH 925 MB WINDS INCREASING TO 35 TO 40
KNOTS IN SOME AREAS. MODEL SOUNDINGS DO NOT SHOW QUITE AS STRONG
AN INVERSION AS ONE WOULD IDEALLY LIKE TO SEE IN ORDER TO MAXIMIZE
WIND PRODUCTION AT THE SURFACE...BUT STILL THINK THAT SOME OF THE
TYPICALLY FAVORED DOWNSLOPE AREAS WILL RECEIVE AT LEAST MINIMAL
ADVISORY CONDITIONS AT TIMES ESPECIALLY TONIGHT AND MONDAY.
EARLIER PUSHED BACK THE START TIME OF THE WIND ADVISORY TO 10 AM
THIS MORNING...AND WILL NOT MAKE ANY FURTHER CHANGES AT THIS
POINT. SEE THE LATEST ADVISORY PRODUCT FOR DETAILS ON AREAS
MOST LIKELY TO BE AFFECTED BY THIS EVENT.

OTHERWISE...MIMIC-TPW SATELLITE IMAGERY AND MODEL DATA CONTINUE
TO SUGGEST THAT AN AREA OF SOMEWHAT ENHANCED LOW LEVEL MOISTURE
WILL CONTINUE MOVING WESTWARD INTO THE STATE THIS MORNING. WOULD
EXPECT THIS ADDITIONAL MOISTURE WITHIN THE BUILDING TRADE FLOW TO
SUPPORT INCREASED SHOWER ACTIVITY ACROSS WINDWARD AND MAUKA
AREAS...WITH SOME SPILLOVER INTO LEEWARD SECTIONS.

STRONG TRADES WILL PREVAIL TONIGHT AND MONDAY AS THE HIGH PASSES
TO OUR NORTH...THEN TRADES SHOULD FALL BACK TO MODERATE LEVELS ON
TUESDAY WITH THE HIGH MOVING FURTHER AWAY TO THE NORTHEAST. THE
OTHER PLAYER IN OUR WEATHER DURING THE EARLY TO MID WEEK PERIOD
WILL BE A SLOW MOVING MID/UPPER TROUGH TO THE SOUTHWEST OF THE
STATE. GUIDANCE IS A BIT MORE EMPHATIC WITH MAINTAINING THIS
FEATURE IN THE MID LEVELS (500 MB) THAN IT WAS PREVIOUSLY... BUT
SHOWS BASICALLY NO REFLECTION IN THE LOWER LEVELS WITH A DISTINCT
DRY LAYER MAINTAINED BETWEEN THE MOISTURE ALOFT AND THE MOIST
TRADE FLOW AT LOW LEVELS. AT THIS POINT IT STILL APPEARS THAT
THERE WILL BE LITTLE IMPACT FROM THIS FEATURE ON SENSIBLE WEATHER
ASIDE FROM CONTINUED BOUTS OF MID/HIGH CLOUDINESS...BUT THIS IS
SOMETHING TO KEEP AN EYE ON THROUGH THE NEXT FEW DAYS. BARRING
ANY SURPRISES...EXPECT SHOWERS TO CONTINUE PRIMARILY ACROSS THE
TYPICAL WINDWARD AND MAUKA AREAS THROUGH MIDWEEK...WITH SOME
SPILLOVER INTO LEEWARD DUE TO THE STRENGTH OF THE TRADES.

LONGER RANGE GUIDANCE INDICATES A STATIC PATTERN ACROSS THE
CENTRAL PACIFIC THROUGH THE NEXT SEVERAL DAYS. MODERATE TRADES
WITH PRIMARILY WINDWARD AND MAUKA SHOWERS ARE LIKELY TO CONTINUE
ACROSS HAWAII FROM WEDNESDAY AT LEAST THROUGH THE END OF THE WEEK.

&&

.AVIATION...
TRADE WIND WILL BE STRENGTHENING THIS MORNING...BECOMING QUITE
WINDY AND GUSTY...AS THE SOURCE OF THE WIND...A STG SFC HIGH PASSES
ALMOST DUE N OF THE ISLAND THROUGH MONDAY. AIRMET TANGO FOR
TURBULENCE TO THE LEE OF THE ALL ISLANDS WILL CONT WELL INTO
TONIGHT AND MONDAY.

THE OTHER CONCERN IS FOR MTN OBSC ASSOCIATED WITH THE LOW CLOUDS AND
SHOWERS RIDING IN WITH THE TRADE WINDS. SO FAR...ALTHOUGH THE CLOUDS
AND SHOWERS HAVE INCREASED...THE CLD BASES ARE JUST ABV MVFR
CRITERIA OF 3K AND THE VIS STAYING ABV 5 MI. WE WILL CONT TO MONITOR
FOR WIDESPREAD MVFR CONDS AS THE DAY PROGRESSES. THESE SHOWERS WILL
BE FAVORING THE WINDWARD AND MTN AREAS WITH A FEW OF THESE SHOWERS
BLOWN DOWNWIND INTO LEEWARD SECTIONS OF THE SMALLER ISLANDS. LEEWARD
BIG ISLAND WILL SEE ITS NORMAL AFTERNOON CLOUDS AND ISOL SHOWERS.

AIRMET ZULU REMAINS IN EFFECT FOR LGT RIME IC DUE TO DENSE LAYERED
CLOUDS OVER THE BIG ISLAND 15K TO 35K. EXPECT THESE CLDS TO THIN OUT
BY 22Z.

OTHERWISE...VFR CONDS PREVAIL.

&&

.MARINE...
ALTHOUGH AN 08Z ASCAT PASS SHOWED WINDS BELOW 25 KNOTS ACROSS
A GOOD PORTION OF THE COASTAL WATERS...WINDS ARE EXPECTED TO
INCREASE TO ADVISORY LEVELS EVERYWHERE LATER TODAY AS HIGH
PRESSURE STRENGTHENS TO OUR NORTH. A SMALL CRAFT ADVISORY REMAINS
POSTED FOR ALL WATERS. WINDS MAY REACH NEAR GALE FORCE AT TIMES
TONIGHT AND MONDAY IN THE ALENUIHAHA CHANNEL.

STRENGTHENING TRADE WINDS WILL PRODUCE SHORT PERIOD...CHOPPY SURF
ALONG EAST FACING SHORES...POSSIBLY REACHING ADVISORY LEVELS
SOMETIME TONIGHT...AND LIKELY REACHING ADVISORY LEVELS FOR MONDAY
THROUGH TUESDAY. OTHERWISE...A SMALL TO MODERATE NORTHWEST SWELL
WILL CONTINUE TODAY...THEN DECLINE TONIGHT AND MONDAY. ANOTHER
MODERATE NORTHWEST SWELL IS EXPECTED TO ARRIVE WEDNESDAY...
PEAK ON THURSDAY...THEN SLOWLY DECLINE ON FRIDAY. RESULTING SURF
ON NORTH AND WEST FACING SHORES WILL REMAIN WELL BELOW ADVISORY
LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 10 AM THIS MORNING TO 6 PM HST MONDAY FOR
WAIANAE COAST-OAHU KOOLAU-OLOMANA-WAIANAE MOUNTAINS-LANAI-
KAHOOLAWE-MAUI WINDWARD WEST-MAUI LEEWARD WEST-MAUI CENTRAL
VALLEY-SOUTH BIG ISLAND-BIG ISLAND NORTH AND EAST-KOHALA-BIG
ISLAND INTERIOR.

SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR ALL HAWAIIAN
WATERS.

&&

$$

DISCUSSION/MARINE...JACOBSON
AVIATION...LAU





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