Satellite Interpretation Message
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000
ATHW40 PHFO 211231
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1230 UTC SUN SEP 21 2014

BASED ON DATA THROUGH 1200 UTC SEPTEMBER 21 2014

REGIONAL SATELLITE IMAGERY SHOWS THAT LOW CLOUDS HAVE DIMINISHED
OVER MOST OF THE MAIN HAWAIIAN ISLANDS SINCE SATURDAY EVENING...
ALTHOUGH CLOUDINESS OF VARYING TYPES CONTINUES NEAR AND OVER THE BIG
ISLAND. LATEST IMAGERY IN FACT SHOWS ISOLATED CLOUD TOPS EXTENDING
AS HIGH AS 40 THOUSAND FEET OVER LEEWARD BIG ISLAND WATERS...AND
ALSO ABOUT 150 TO 275 MILES EAST OF WINDWARD BIG ISLAND...WHERE
THUNDERSTORMS ARE LIKELY OCCURRING. WATER VAPOR IMAGERY SHOWS A
SHARP TROUGH ALOFT AXIS STRADDLING THE ISLAND CHAIN NEAR MAUI...AND
THE PRESENCE OF THIS FEATURE IS LIKELY ADDING INSTABILITY TO AN AREA
WHERE INCREASED LOW LEVEL MOISTURE IS NOTED.

LIGHT WINDS PREVAIL OVER THE ISLANDS...BUT FAVOR AN EASTERLY
DIRECTION AT CLOUD LEVEL. WHILE THE LIGHT EASTERLY COMPONENT OF THE
WIND AT CLOUD LEVEL HAS PUSHED FEW TO SCATTERED LOW CLOUDS AND
ISOLATED SHOWERS OVER WINDWARD PORTIONS OF THE ISLANDS
OVERNIGHT...THE OVERALL TREND HAS BEEN TOWARD CLEARING OF SKIES OVER
THE ISLANDS SINCE SUNSET ON SATURDAY. MEANWHILE...SCATTERED TO
LOCALLY OVERCAST LAYERED CLOUDS ARE OVER THE BIG ISLAND...ADJACENT
LEEWARD WATERS...AND OVER WATERS EAST AND SOUTHEAST OF THE BIG
ISLAND. INCREASED MOISTURE IN THE VICINITY OF THE BIG ISLAND IS
ASSOCIATED WITH WEAK TROPICAL DISTURBANCES PASSING TO THE SOUTH...
WITH THIS MOISTURE BEING ENHANCED DUE TO A TROUGH ALOFT IN THE
VICINITY.

WATER VAPOR IMAGERY SHOWS THAT THE AXIS OF THIS SHARP TROUGH ALOFT
IS OVER MAUI COUNTY...MOVING SOUTHEAST NEAR 10 MPH. WITH THE TROUGH
ALIGNED IN THIS MANNER...WINDS ALOFT OVER KAUAI AND OAHU ARE FROM
THE EAST-NORTHEAST...WHILE WINDS ALOFT OVER THE BIG ISLAND ARE
FROM THE SOUTHWEST. A RIDGE ALOFT IS SEEN TO THE DISTANT SOUTHEAST
OF THE ISLANDS...AND STRONG SOUTHWESTERLY WINDS ALOFT ARE BETWEEN
THE TROUGH AND THE RIDGE. THIS IS RESULTING IN UPPER LEVEL WINDS
THAT ARE NOT CONDUCIVE FOR THE FURTHER DEVELOPMENT OF A WEAK
WESTWARD-MOVING TROPICAL DISTURBANCE LOCATED ABOUT 425 MILES
SOUTHWEST OF OAHU. ASSOCIATED SHOWERS AND THUNDERSTORMS HAVE
DIMINISHED NEAR THIS DISTURBANCE OVER THE PAST 6 HOURS...BUT
MOISTURE EXTENDING NORTH AND EAST FROM THE DISTURBANCE HAS HELPED TO
FUEL THE THUNDERSTORMS DESCRIBED EARLIER NEAR THE BIG ISLAND.

WHILE MOST ISLANDS LIE IN AN AREA OF RELATIVELY FEW LOW CLOUDS ON
THE LARGE SCALE...AN EAST TO WEST ORIENTED CLOUD BAND...MARKING A
STALLED AND WEAKENING FRONT...IS ABOUT 500 TO 600 MILES NORTH OF
OAHU. ANOTHER CLUSTER OF NEARLY STATIONARY LOW CLOUDS IS ABOUT 300
TO 400 MILES NORTH OF MAUI COUNTY...ASSOCIATED WITH A WEAK SURFACE
TROUGH THAT EXTENDS SOUTHWARD TOWARD OAHU.

$$

BIRCHARD





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