Drought in Hawaii, February 1 to 28, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST FRI JAN 31 2014

.SYNOPSIS...
A FRONT APPROACHING THE ISLANDS FROM THE NORTHWEST WILL KEEP
SOUTHERLY WINDS OVER THE ISLANDS TONIGHT...ALONG WITH SHOWERS MOVING
OVER THE ISLANDS FROM SOUTH TO NORTH. THE FRONT IS EXPECTED TO MOVE
OVER KAUAI SATURDAY...AND THEN STALL OUT NEAR THE CENTRAL ISLANDS BY
SUNDAY. A DEVELOPING SURFACE TROUGH OVER THE ISLANDS MONDAY NIGHT
WILL HELP TO INVIGORATE LEFT OVER MOISTURE...BRINGING THE
POSSIBILITY OF LOCALLY HEAVY RAIN TO THE SMALLER ISLANDS.

&&

.DISCUSSION...
NO CHANGES IN STORE AT THIS TIME FOR THE SHORT TERM. SOUTHERLY WINDS
AHEAD OF THE APPROACHING COLD FRONT WILL CONTINUE TO BRING SHOWERS
OVER THE ISLANDS OVERNIGHT. THE SHOWERS HAVE BEEN CONCENTRATED NEAR
THE SMALLER ISLANDS AND THAT IS EXPECTED TO CONTINUE THROUGHOUT THE
NIGHT.

THE MODELS REMAIN IN GOOD AGREEMENT WITH THE LOW FAR NORTHWEST OF
THE ISLANDS REMAINING NEARLY STATIONARY FOR THE NEXT 24 HOURS...AND
THEN LIFTING TO THE NORTH NORTHEAST THROUGH MONDAY AFTERNOON. THE
FRONT STILL LOOKS TO PASS OVER KAUAI TOMORROW...WITH CLOUDS AND
SHOWERS IMPACTING THE SMALLER ISLANDS THROUGH SUNDAY NIGHT AS THE
FRONT SETTLES NEAR THE CENTRAL ISLANDS.

THE NEXT SIGNIFICANT WEATHER CHALLENGE IS INTRODUCED DURING THE
START OF THE WORK WEEK. THE MODELS START TO DIVERGE IN THE
PARTICULARS...BUT THERE IS GENERAL AGREEMENT WITH A SURFACE TROUGH
FORMING ALONG THE FRONTAL REMNANTS OVER THE CENTRAL ISLANDS.
SLIGHTLY COLDER TEMPERATURES MOVE IN AT 700 MB AND 500 MB MONDAY
NIGHT/TUESDAY. THE ECMWF IS COLDER AT 700 MB THAN THE GFS...WHILE
BOTH ARE PRETTY SIMILAR AT 500 MB. TEMPERATURES AT 500 MB WOULD BE
JUST BARELY WITHIN 1 STANDARD DEVIATION FROM NORMAL....WHILE 700 MB
TEMPERATURES WOULD BE JUST OUTSIDE NORMAL BASED ON THE ECMWF. THE
SURFACE TROUGH...COMBINED WITH THE UPPER LEVEL WIND FLOW PATTERN
WOULD CONTINUE TO BRING IN LOW LEVEL MOISTURE FROM THE
SOUTH...BRINGING PRECIPITABLE WATER VALUES HIGHER THAN NORMAL.

AT THIS TIME...CONSIDER THE MOST SIGNIFICANT THREAT TO BE THAT OF
SOME HEAVY RAINS...PARTICULARLY OVER THE SMALLER ISLANDS MONDAY
NIGHT THROUGH TUESDAY. LOOKING AT THE LATEST GUIDANCE...THINK THE
THREAT IS GREATEST OVER KAUAI AND OAHU...BUT MAUI COUNTY WOULD BE
CLOSE ENOUGH. WITH THE COLDEST UPPER LEVEL TEMPERATURES OVER
KAUAI...THE ATMOSPHERE COULD BE UNSTABLE ENOUGH TO TRIGGER A
THUNDERSTORM OR TWO MONDAY NIGHT OR TUESDAY MORNING. WOULD WANT TO
SEE MORE INSTABILITY AND MODEL AGREEMENT BEFORE EXPANDING EITHER THE
HEAVY RAIN OR THUNDERSTORM AREA.

THE ECMWF AND GFS STILL DEVELOP A SURFACE LOW NORTHWEST OF THE
ISLANDS WEDNESDAY...BUT ARE NOT AS AGGRESSIVE WITH THE SYSTEM AS 24
HOURS AGO. THIS WILL LIKELY KEEP SHOWERS OVER THE ISLANDS INTO THE
MIDDLE OF THE WEEK. THE MODELS VARY ON HOW SUCCESSFUL A HIGH
PRESSURE RIDGE IS IN BUILDING NORTH OF THE ISLANDS FOR THE SECOND
HALF OF THE WEEK.

&&

.MARINE...
WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY /SCA/ LEVEL
THROUGH THE FORECAST PERIOD. A NEW LARGE NORTHWEST SWELL IS EXPECTED
TO ARRIVE LATE SATURDAY AND WILL LIKELY BRING ADVISORY LEVEL SURF
SUNDAY THROUGH MONDAY. THIS SWELL MAY ALSO REQUIRE A SCA FOR EXPOSED
AREAS. ANOTHER MODERATE SIZED NORTHWEST SWELL WILL ARRIVE LATE
TUESDAY NIGHT INTO WEDNESDAY. CURRENT INDICATIONS ARE THAT SURF
WILL REMAIN BELOW ADVISORY CRITERIA WITH THAT SWELL.

&&

.AVIATION...
AIRMET SIERRA IS IN EFFECT FOR KAUAI OAHU MOLOKAI AND LANAI FOR
MOUNTAIN OBSCURATION BELOW 1500 FEET. LOW CLOUDS WILL LIKELY CAUSE
TEMPO MVFR CONDITIONS AT THE TERMINALS WEST OF MAUI OVERNIGHT...
WITH TEMPO IFR EXPECTED IN FOG ACROSS CENTRAL LANAI. TEMPO MVFR
CONDITIONS MAY SPREAD EAST SATURDAY AS A FRONT APPROACHES FROM THE
NORTHWEST.

&&

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

&&

DISCUSSION/MARINE...M BALLARD
AVIATION...POWELL