Satellite Interpretation Message
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000
ATHW40 PHFO 061837
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1830 UTC SAT FEB 06 2016

BASED ON DATA THROUGH 1800 UTC FEBRUARY 06 2016

SATELLITE IMAGES CENTERED OVER THE MAIN HAWAIIAN ISLANDS SHOW THAT
SKY COVER VARIES WILDLY FROM ISLAND TO ISLAND...RANGING FROM
COMPLETELY CLEAR TO ENTIRELY OVERCAST. INITIAL VISIBLE IMAGES OF
THE DAY INDICATE THAT SUNNY SKIES PREVAIL OVER NIIHAU...KAUAI AND
THE BIG ISLAND. MOSTLY SUNNY SKIES ARE OVER MAUI COUNTY...BUT
SCATTERED TO BROKEN SHOWERY LOW CLOUDS ARE NOTED OVER NEAR SHORE
WATERS SOUTH OF MAUI...AND WEST OF THE BIG ISLAND. MEANWHILE...
SKIES ARE COMPLETELY OVERCAST OVER OAHU AND SURROUNDING NEAR
SHORE WATERS...DUE TO THE PRESENCE OF A SLOW-MOVING...NORTHEAST
TO SOUTHWEST ORIENTED...BAND OF LOW CLOUDS.

NOT ONLY DOES SKY COVER VARY DRASTICALLY FROM PLACE TO PLACE
ACROSS THE STATE...ANIMATION OF SATELLITE IMAGERY SHOWS THAT
STRONG GRAVITY WAVES MOVING RAPIDLY NORTHWEST TO SOUTHEAST ACROSS
THE AREA ARE DRAMATICALLY CHANGING CLOUD COVER OVER ANY PARTICULAR
AREA. ONE EXAMPLE IS THE SKY COVER OVER OAHU...AND ITS EVOLUTION
OVER THE PAST 6 HOURS. SKIES WERE NEARLY CLEAR OVER THE ISLAND
AROUND 2 AM BUT THEN LOW CLOUDS QUICKLY INCREASED BETWEEN OAHU AND
KAUAI BY 4 AM...ONLY TO SEE A BRIEF PERIOD OF CLEARING AROUND 6 AM
TRANSITION TO THE CURRENT OVERCAST CONDITIONS. LOW CLOUDS ARE
MOVING TOWARD THE WEST NEAR AND SOUTH OF THE BIG ISLAND...ARE
NEARLY STATIONARY NEAR MAUI AND OAHU...AND ARE MOVING TOWARD THE
SOUTHEAST NEAR AND NORTHWEST OF KAUAI. THESE CLOUD MOTIONS
HIGHLIGHT THE WEAK LOW-LEVEL CONVERGENCE THAT IS LIKELY TO BE AT
LEAST PARTIALLY RESPONSIBLE FOR THE SHOWERY LOW CLOUDS NEAR OAHU
THIS MORNING.

THE LEADING EDGE OF A 150 TO 200 MILE WIDE BAND OF BROKEN TO
OVERCAST SHOWERY AND STABLE LOW CLOUDS LIES ABOUT 175 MILES
NORTHWEST OF KAUAI...WHICH IS MOVING SOUTHEAST AT ABOUT 20 MPH.
THIS CLOUD BAND MARKS A COLD FRONT THAT EXTENDS FROM NEAR 30N 153W
TO NORTHWEST OF KAUAI...TO 18N 180. NORTHWEST OF THIS BOUNDARY...
BROKEN TO OVERCAST SHOWERY CUMULUS AND TOWERING CUMULUS CLOUDS
PREVAIL...INDICATIVE OF AN UNSTABLE AND COLD AIR MASS.

WATER VAPOR IMAGERY SHOWS THAT A PERSISTENT RIDGE OF HIGH PRESSURE
IN THE MID AND UPPER LEVELS OF THE ATMOSPHERE CONTINUES TO
PREVAIL SOUTH AND SOUTHWEST OF THE ISLANDS...BUT ALSO SHOWS THAT
IT HAS WEAKENED AND BEEN SUPPRESSED SOUTHWARD FROM WHERE IT WAS
EARLIER IN THE WEEK. THIS APPEARS TO HAVE OCCURRED IN RESPONSE TO
A SOUTHWARD DIP IN THE JET STREAM TO THE NORTH OF THE
ISLANDS...WITH A TROUGH ALOFT SUPPORTING THE SURFACE FRONT
DESCRIBED ABOVE. ALTHOUGH THIS TROUGH IS NOT VERY SHARP SOUTH OF
30N...IT LIES ALONG A LINE FROM 30N 155W TO 25N 156W TO NEAR KAUAI
AND OAHU TO 21N 166W...AND IS MOVING RAPIDLY EAST ACROSS THE AREA
AT SPEEDS BETWEEN 60 AND 70 MPH.

$$

BIRCHARD


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