Wildfire in Hawaii, March 24 to 31, 2016

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1005 AM HST THU MAR 24 2016

.SYNOPSIS...
A WEAK TROUGH OF LOW PRESSURE WILL REMAIN WEST OF THE STATE
TODAY...THEN SLOWLY PUSH EASTWARD ACROSS THE ISLAND CHAIN TONIGHT
THROUGH SATURDAY. AN UNSTABLE AIRMASS IS EXPECTED TO ACCOMPANY THE
TROUGH AS IT MOVES THROUGH THE AREA...BRINGING UNSETTLED WEATHER
ALONG WITH THE POTENTIAL FOR HEAVY RAINFALL AND THUNDERSTORMS.
THE TROUGH WILL SHIFT EAST OF THE STATE ON SUNDAY...WITH A DRIER
AIRMASS MOVING BACK OVER THE ISLANDS. A COLD FRONT WILL THEN
APPROACH FROM THE NORTHWEST ON MONDAY AND SLOWLY PUSH
SOUTHEASTWARD THROUGH THE STATE MONDAY NIGHT THROUGH TUESDAY
NIGHT. HIGH PRESSURE WILL THEN BUILD NORTH OF THE STATE DURING THE
MIDDLE TO LATTER PART OF NEXT WEEK...WITH LIGHT TO MODERATE TRADES
ALONG WITH A COOLER AND DRIER AIRMASS RETURNING TO THE ISLANDS.

&&

.DISCUSSION...
CURRENTLY AT THE SURFACE...A TROUGH OF LOW PRESSURE RUNS FROM
SOUTHWEST TO NORTHEAST BETWEEN 20N165W AND 30N157W...OR AROUND 160
MILES TO THE WEST-NORTHWEST OF KAUAI. MEANWHILE...FAR NORTHEAST OF
THE ISLANDS...A 1031 MB HIGH IS CENTERED NEAR 36N134W WITH RIDGING
EXTENDING SOUTHWESTWARD INTO THE BIG ISLAND. ALOFT...A SHORTWAVE
TROUGH IS EVIDENT IN WATER VAPOR IMAGERY AROUND 25N175W...AND THIS
FEATURE WILL HAVE A BIG IMPACT ON THE LOCAL WEATHER OVER THE NEXT
SEVERAL DAYS. VISIBLE SATELLITE IMAGERY SHOWS CLEAR TO PARTLY
CLOUDY SKIES IN PLACE ACROSS THE AREA THIS MORNING...WITH RADAR
IMAGERY SHOWING A FEW ISOLATED SHOWERS MAINLY ACROSS THE COASTAL
WATERS. MAIN SHORT TERM CONCERNS FOR TODAY REVOLVE AROUND RAIN
CHANCES AND THE POTENTIAL FOR THUNDERSTORMS.

TODAY...
THE SURFACE TROUGH OF LOW PRESSURE WEST OF KAUAI...WILL REMAIN
NEARLY STATIONARY THROUGH THE DAY. MEANWHILE...THE SHORTWAVE
TROUGH WELL WEST-NORTHWEST OF THE STATE...WILL DIG SOUTHEASTWARD
THROUGH THE DAY...RESULTING IN AMPLIFICATION OF AN UPPER LEVEL
TROUGH TO THE WEST OF KAUAI BY LATE THIS AFTERNOON. AS THIS
OCCURS...THE PREVAILING SOUTHEASTERLY BOUNDARY LAYER WINDS WILL
BRING INCREASING DEEP LAYER MOISTURE NORTHWARD INTO THE
STATE...PARTICULARLY ACROSS KAUAI...WHICH WILL BE IN CLOSER
PROXIMITY TO THE SURFACE TROUGH. THE ISLANDS WILL REMAIN IN A
WEAK WIND REGIME...WITH SEA BREEZES EXPECTED IN MOST AREAS. THE
COMBINATION OF SEA BREEZE CONVERGENCE...TERRAIN
ENHANCEMENT...ALONG WITH PRECIPITABLE WATER /PW/ VALUES BETWEEN
1.3 AND 1.5 INCHES ACROSS THE STATE...SHOULD ALLOW FOR DECENT
COVERAGE OF SHOWERS ACROSS THE INTERIOR OF THE ISLANDS THIS
AFTERNOON. AS FOR THUNDER POTENTIAL...MID-LEVEL LAPSE RATES AND
MOISTURE PROFILES WON/T BE PARTICULARLY CONDUCIVE FOR THUNDERSTORM
DEVELOPMENT ACROSS MOST OF THE STATE. THE ONE EXCEPTION MAY BE
ACROSS THE WESTERN ISLANDS...PARTICULARLY NIIHAU AND KAUAI...WHERE
SURFACE BASED CAPE VALUES RISE TO AROUND 1500 J/KG AND 500
MILLIBAR TEMPERATURES DROP TO AROUND -11 TO -12 CELSIUS. AS A
RESULT...WE WILL UPDATE THE FORECAST TO INCLUDE A SLIGHT CHANCE OF
THUNDER ACROSS THE WESTERN ISLANDS.

TONIGHT...
THE UPPER LEVEL TROUGH WILL CONTINUE TO AMPLIFY WEST OF THE STATE
THROUGH THE NIGHT...SHIFTING THE SURFACE TROUGH OF LOW PRESSURE
NEAR KAUAI BY DAYBREAK FRIDAY. DEEP LAYER MOISTURE WILL CONTINUE
TO INCREASE ACROSS THE ISLANDS IN ADVANCE OF THE TROUGH...WITH PW
VALUES RISING TO BETWEEN 1.5 AND 1.7 INCHES ACROSS OAHU...KAUAI
AND NIIHAU BY DAYBREAK FRIDAY. 500 MILLIBAR TEMPERATURES WILL
CONTINUE TO COOL...DROPPING TO BETWEEN -12 AND -14 CELSIUS ACROSS
THE WESTERN HALF OF THE STATE. AS A RESULT...WE EXPECT AN INCREASE
IN SHOWER COVERAGE PARTICULARLY ACROSS THE WESTERN HALF OF THE
STATE...WHERE THE POTENTIAL FOR HEAVY RAINFALL AND THUNDERSTORMS
WILL ALSO EXIST.

FRIDAY AND FRIDAY NIGHT...
THINGS GET A BIT MORE INTERESTING ACROSS THE ISLANDS...AS THE
SURFACE TROUGH TRACKS STEADILY EASTWARD THROUGH KAUAI AND OAHU
DURING THE DAY AND THROUGH MAUI COUNTY AND INTO THE BIG ISLAND
OVERNIGHT. AT THE SAME TIME...THE UPPER LEVEL TROUGH IS EXPECTED
TO FURTHER AMPLIFY AND POSSIBLY CLOSE OFF AS IT PIVOTS EASTWARD
THROUGH THE ISLAND CHAIN. WITH PLENTY OF DEEP LAYER MOISTURE IN
PLACE WITH PW VALUES AROUND OR IN EXCESS OF 1.5 INCHES...500
MILLIBAR TEMPERATURES BETWEEN -12 AND -14 CELSIUS...AND 0-6
KILOMETER BULK SHEAR VALUES BETWEEN 25 AND 30 KNOTS...SOME
ORGANIZED THUNDERSTORMS WILL BE POSSIBLE ACROSS THE ISLANDS. THE
OVERLYING CLOUD COVER THROUGH THE DAY WILL HAVE A BIG IMPACT ON
WHETHER OR NOT SOME STRONG THUNDERSTORMS ARE ABLE TO
DEVELOP...BUT IF ENOUGH HEATING IS REALIZED WHICH IS SUGGESTED BY
SOME OF THE MODELS SHOWING SURFACE BASED CAPE VALUES RISING TO
BETWEEN 2000 AND 2500 J/KG...SOME OF THE STRONGER STORMS MAY
BE CAPABLE OF PRODUCING SMALL HAIL AND GUSTY WINDS. IN FACT...A
SEVERE STORM OR TWO CAN/T ENTIRELY BE RULED OUT.

SATURDAY AND SATURDAY NIGHT...
THE UPPER LEVEL TROUGH WILL PIVOT EASTWARD THROUGH THE
DAY...SHIFTING THE SURFACE TROUGH EAST OF THE BIG ISLAND BY
SATURDAY EVENING. DEEP LAYER MOISTURE AND MID-LEVEL TEMPERATURES
WILL REMAIN CONDUCIVE FOR THUNDERSTORM DEVELOPMENT OVER MAUI
COUNTY AND THE BIG ISLAND THROUGH SATURDAY EVENING...SO WILL KEEP
A MENTION OF THUNDERSTORMS IN THE FORECAST IN THESE AREAS.
ELSEWHERE...DEEP LAYER MOISTURE AND THE CHANCES FOR RAIN WILL BE
DECREASING BEHIND THE PASSAGE OF THE UPPER LEVEL TROUGH.

SUNDAY THROUGH NEXT THURSDAY...
THE 12Z ECMWF AND 12Z GFS BOTH SHOW THE SURFACE AND UPPER LEVEL
TROUGHS EAST OF THE BIG ISLAND BY DAYBREAK SUNDAY...WITH A DRIER
AIRMASS OVERSPREADING THE STATE. A COLD FRONT WILL THEN APPROACH
THE STATE FROM THE NORTHWEST ON MONDAY...AND TRACK SOUTHEASTWARD
DOWN THE ISLAND CHAIN MONDAY NIGHT THROUGH TUESDAY
NIGHT...WITH A BAND OF SHOWERS LIKELY ACCOMPANYING THE FRONT.
HIGH PRESSURE IS THEN EXPECTED TO BUILD NORTH OF THE STATE DURING
THE MIDDLE TO LATTER PART OF NEXT WEEK...WITH RELATIVELY DRY
CONDITIONS EXPECTED ACROSS THE AREA.

&&

.AVIATION...
RELATIVELY MOIST LIGHT SE BACKGROUND FLOW COULD LEAD TO SOME SEA
BREEZE FORCED CONVECTION OVER THE ISLANDS THIS AFTERNOON WITH
LOCALIZED MVFR AND BRIEF IFR POSSIBLE IN SHRA AFTER 22Z. APPROACHING
SHORTWAVE TROUGH WILL INCREASE THE CHANCE FOR MVFR AND MT OBSC WITH
ISOL IFR IN SHRA/+TSRA ESPECIALLY NEAR KAUAI STARTING THIS EVENING
AND POSSIBLY GETTING TO OAHU AND MAUI COUNTY LATER IN THE NIGHT.
CONFIDENCE ON DETAILS OF CONVECTIVE EVOLUTION DECREASES QUITE A BIT
BY LATE NIGHT AS OUR HIGHER RESOLUTION GUIDANCE HAS LARGE
DIFFERENCES IN THE POSSIBLE SOLUTIONS.

&&

.MARINE...
THERE ARE NO MARINE WARNINGS IN EFFECT. WATERS AROUND HAWAII ARE
EXPECTED TO REMAIN QUIET THROUGH MONDAY WITH ONLY A SMALL NORTH
NORTHWEST SWELL PEAKING TONIGHT FOLLOWED BY A SMALL NORTHWEST SWELL
THIS WEEKEND. SURF WILL REMAIN BELOW ADVISORY LEVELS AND WINDS ARE
EXPECTED TO REMAIN LIGHT. SMALL BACKGROUND SOUTH SWELLS WILL
CONTINUE THROUGH THE PERIOD. A VERY LARGE NORTHWEST SWELL IS
FORECAST TO ARRIVE TUESDAY AND PEAK LATE TUESDAY NIGHT...POSSIBLY
BRINGING WARNING LEVEL SURF TO NORTH AND WEST FACING SHORES.

A SLIGHT CHANCE OF THUNDERSTORMS IS POSSIBLE STARTING THIS
AFTERNOON AND CONTINUING INTO FRIDAY...ESPECIALLY FOR WESTERN
AREAS. IF CONDITIONS WARRANT...SHORT-FUSED SPECIAL MARINE
WARNINGS MAY NEED TO BE ISSUED.

&&

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

&&

DISCUSSION...JELSEMA
AVIATION...R BALLARD
MARINE...EATON