Current Conditions
Temp3.5 C
RH9 %
WindSSE 12 mph
RoadOpen
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

577
FXHW60 PHFO 260646
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
846 PM HST FRI JUL 25 2014

.SYNOPSIS...
MODERATE TRADE WINDS WILL FOCUS SHOWERS MAINLY ACROSS WINDWARD
AND MAUKA AREAS. AN INCREASE IN SHOWER ACTIVITY IS EXPECTED TO
MOVE FROM EAST TO WEST ACROSS THE STATE DURING THE WEEKEND.
TRADES MAY STRENGTHEN SOMEWHAT EARLY NEXT WEEK.

&&

.DISCUSSION...
A QUIET LATE JULY EVENING IS IN PROGRESS ACROSS THE STATE. RADAR
LOOPS AND RAIN GAUGE DATA SHOW PASSING TRADE SHOWERS ACROSS SOME
WINDWARD AREAS...WITH RAINFALL ACCUMULATIONS GENERALLY REMAINING
ON THE LIGHT SIDE. A TYPICAL SUMMERTIME SURFACE PATTERN PREVAILS...
WITH THE NORTHEAST PACIFIC HIGH CENTERED ABOUT 1400 MILES
NORTHEAST OF HONOLULU. A WEAK LOW PRESSURE AREA IS LOCATED ABOUT
720 MILES SOUTH SOUTHEAST OF SOUTH POINT ON THE BIG ISLAND...AND
IS BEING MONITORED FOR SIGNS OF DEVELOPMENT WHILE MOVING TO THE
WEST. WATER VAPOR IMAGERY DEPICTS A MID LEVEL RIDGE EXTENDING
FROM THE BIG ISLAND EASTWARD...WITH AN UPPER LEVEL TROUGH LOCATED
SEVERAL HUNDRED MILES NORTHEAST OF KAUAI. THE 00Z SOUNDINGS SHOW A
WELL DEFINED INVERSION BASED AROUND 7000 FEET...WITH NEAR NORMAL
PRECIPITABLE WATER VALUES OF BETWEEN 1.3 AND 1.4 INCHES. MIMIC-TPW
IMAGERY SHOWS AN AREA OF HIGHER MOISTURE (PWATS 1.5 TO 1.7 INCHES)
APPROACHING THE STATE FROM THE EAST...WITH THE LEADING EDGE ABOUT
100 MILES SOUTHEAST OF THE BIG ISLAND.

THROUGH THE OVERNIGHT...WOULD EXPECT TRADE SHOWERS TO INCREASE
ACROSS WINDWARD AREAS IN THE TYPICAL MANNER...WITH A FEW OF THE
SHOWERS SPILLING OVER INTO SOME LEEWARD AREAS. THE HIGHEST RAIN
CHANCES SHOULD OCCUR ACROSS WINDWARD SLOPES OF THE BIG ISLAND AND
HALEAKALA...AS THE AREA OF ENHANCED MOISTURE MOVES IN LATE
TONIGHT. THE EXISTING FORECAST REFLECTS THE ABOVE THINKING...
AND NO UPDATES ARE PLANNED FOR THIS EVENING.

LITTLE CHANGE IS EXPECTED TO THE OVERALL MODERATE TRADE WIND
PATTERN THROUGH THE WEEKEND. MODELS APPEAR TO INITIALIZE THE
AREA OF HIGHER MOISTURE CURRENTLY JUST EAST OF THE STATE
REASONABLY WELL...AND MOVE THIS AREA STEADILY WESTWARD THROUGH
SUNDAY. DURING THIS TIME...THE UPPER LEVEL TROUGH INITIALLY
NORTHWEST OF KAUAI WILL MOVE EASTWARD...PASSING NORTH OF THE STATE
SUNDAY AND SUNDAY NIGHT. WOULD EXPECT THE TRADE INVERSION TO RISE
AND WEAKEN A BIT IN RESPONSE...WHICH COMBINED WITH THE ADDITIONAL
MOISTURE MOVING THROUGH COULD PRODUCE A FEW LOCALLY HEAVIER
SHOWERS AT TIMES. PERSISTENT MODERATE TRADE FLOW SHOULD KEEP THE
SHOWERS MOVING ALONG HOWEVER. POPS WILL REMAIN QUITE HIGH OVER
WINDWARD AND MAUKA SECTIONS ESPECIALLY DURING THE NIGHT AND EARLY
MORNING HOURS...WITH SOME SPILLOVER INTO LEEWARD SECTIONS OF THE
SMALLER ISLANDS.

HEADING INTO NEXT WEEK...THE NORTHEAST PACIFIC HIGH IS FORECAST
TO WEAKEN SOMEWHAT AS A COLD FRONT MOVES EASTWARD NORTH OF
30N...BUT AT THE SAME TIME A TROPICAL LOW PASSING WELL SOUTH OF
THE STATE MAY BE ABLE TO MAINTAIN OR EVEN TIGHTEN THE PRESSURE
GRADIENT LOCALLY. OVERALL WOULD EXPECT A TYPICAL TRADE WIND
PATTERN TO PREVAIL FOR MONDAY THROUGH AT LEAST TUESDAY...WITH
PASSING SHOWERS MAINLY AFFECTING WINDWARD AND MAUKA.

TOWARD THE MIDDLE TO LATER PART OF NEXT WEEK...SOME OF THE MODEL
GUIDANCE CONTINUES TO BRING ANOTHER SURGE OF DEEP TROPICAL
MOISTURE UP TOWARD THE STATE FROM THE SOUTHEAST. THIS MOISTURE
WOULD BE ASSOCIATED WITH THE REMNANTS OF CURRENT EAST PACIFIC
TROPICAL STORM GENEVIEVE. THE GUIDANCE SUITE HAS BEEN RATHER
INCONSISTENT WITH BOTH THE TIMING AND EXTENT OF ANY POSSIBLE
MOISTURE SURGE. THERE IS THE POTENTIAL FOR ANOTHER ROUND OF
HEAVY SHOWERS ACROSS THE STATE LATER NEXT WEEK AND INTO NEXT
WEEKEND...BUT FORECAST UNCERTAINTY REMAINS QUITE HIGH AT THIS
POINT.

&&

.AVIATION...
TEMPO MVFR CONDITIONS WILL LIKELY OCCUR THIS EVENING THROUGH
SATURDAY MORNING...MAINLY OVER WINDWARD AND MAUKA SECTIONS...AS
LOW CLOUDS AND ACCOMPANYING SHOWERS RIDE THE TRADE WINDS. VFR WILL
OTHERWISE PREDOMINATE.

&&

.MARINE...
THERE IS NO RECENT ASCAT DATA AVAILABLE ACROSS THE HAWAIIAN
COASTAL WATERS...BUT AN EARLIER ASCAT PASS ACROSS THE WESTERN
WATERS AND CURRENT MESONET DATA IMPLY THAT WINDS ARE LIKELY BELOW
SMALL CRAFT ADVISORY /SCA/ CRITERIA THROUGHOUT THE AREA. THE
NORTHEAST PACIFIC SURFACE HIGH WILL MOVE SLIGHTLY FURTHER AWAY
FROM THE STATE DURING THE WEEKEND...BUT A LOW PRESSURE AREA
PASSING WELL SOUTH OF THE AREA MAY TIGHTEN THE GRADIENT ACROSS
THE ISLANDS SOMEWHAT. WINDS MAY INCREASE TO SCA LEVELS AS EARLY
AS SUNDAY EVENING ACROSS THE TYPICALLY WINDIER AREAS AROUND MAUI
COUNTY AND THE BIG ISLAND...BUT THIS REMAINS UNCERTAIN. SCA
CONDITIONS WILL REMAIN POSSIBLE IN THE TYPICALLY WINDY AREAS
THROUGH MUCH OF NEXT WEEK.

AS FOR SURF...A SMALL SSW SWELL MAY PRODUCE A MINOR BUMP ON SOUTH
FACING SHORES SATURDAY NIGHT AND SUNDAY. SHORT PERIOD TRADE WIND
SWELL WILL CONTINUE ACROSS EAST FACING SHORES...POSSIBLY
INCREASING A BIT EARLY NEXT WEEK IF TRADES STRENGTHEN. NO
SIGNIFICANT NORTH THROUGH WEST SWELLS ARE EXPECTED THROUGH THE
NEXT SEVERAL DAYS. OVERALL...SURF WILL REMAIN WELL BELOW ADVISORY
LEVELS ON ALL SHORES THROUGH THE WEEKEND AND INTO THE FIRST PART
OF NEXT WEEK.

&&

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

&&

$$

DISCUSSION/MARINE...JACOBSON
AVIATION...KINEL




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