Wildfire in Hawaii, May 19, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST TUE MAY 19 2015

.SYNOPSIS...
TRADE WINDS WILL START TO DIMINISH ON WEDNESDAY...THEN BREAK DOWN
INTO A LIGHT SEA BREEZE PATTERN ON THURSDAY AS A WEAKENING FRONT
APPROACHES FROM THE NORTHWEST. THIS FRONT WILL REACH KAUAI ON
FRIDAY...THEN DISSIPATE OVER THE WEEKEND AS IT MOVES DOWN THE ISLAND
CHAIN. A WEAK HIGH WILL BUILD NORTH OF THE STATE BEHIND THE
FRONT...BRINGING A RETURN TO LIGHT TRADE WINDS EARLY NEXT WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A WEAK UPPER LEVEL LOW NORTH OF KAUAI...
WITH A RIDGE FARTHER NORTH. A 60 KT WEST-SOUTHWESTERLY JET IS
LOCATED OVER THE SOUTHERN HALF OF THE STATE. AT THE SURFACE...HIGH
PRESSURE IS NEARLY STATIONARY ABOUT 700 MILES NORTH-NORTHEAST OF THE
STATE...WITH A COLD FRONT FAR TO THE NORTHWEST. 00Z SOUNDINGS SHOW
INVERSIONS RANGING FROM 5KFT AT LIHUE TO 7KFT AT HILO...WITH
PRECIPITABLE WATERS OF 0.8-0.9 INCHES RESPECTIVELY. EARLY AFTERNOON
MIMIC TOTAL PRECIPITABLE WATER IMAGERY SHOWS THIS DRIER AIR...
GREATEST ACROSS THE WESTERN HALF OF THE STATE...WITH A POCKET OF
HIGHER MOISTURE JUST OUTSIDE OF THE COASTAL WATERS EAST OF THE BIG
ISLAND.

CONDITIONS HAVE BEEN DRY OVER MUCH OF THE STATE...WITH ONLY A
COUPLE GAGES RECEIVING A HUNDREDTH OF AN INCH THIS AFTERNOON.
SHOWERS HAVE BEEN MORE ACTIVE ACROSS WINDWARD BIG ISLAND...WHERE A
NUMBER OF LOCATIONS RECEIVED UP TO A TENTH OF AN INCH DURING THE
AFTERNOON. THE NEXT POCKET OF MOISTURE...CURRENTLY SEEN AS AN AREA
OF SHOWERY CLOUDS JUST MOVING INTO THE WINDWARD COASTAL WATERS
NORTHEAST AND EAST OF THE BIG ISLAND...WILL AFFECT MAINLY THE BIG
ISLAND AND MAUI TONIGHT...ONCE AGAIN ENHANCING SHOWERS ACROSS
PRIMARILY WINDWARD SECTIONS. WINDWARD AND MAUKA SHOWERS WILL ALSO
CONTINUE ACROSS KAUAI AND OAHU...WITH MUCH LIGHTER RAINFALL AMOUNTS.

THE COLD FRONT TO THE NORTHWEST WILL APPROACH THE ISLANDS...
INITIALLY SHIFTING THE RIDGE SOUTHWARD ACROSS US ON THURSDAY. TRADE
WINDS WILL DIMINISH A BIT ON WEDNESDAY...THEN BREAK DOWN COMPLETELY
ON THURSDAY BENEATH THE RIDGE. WINDS WILL BE DOMINATED BY LOCALLY
DRIVEN DAYTIME SEA BREEZES AND NIGHTTIME LAND BREEZES. FORECAST
SOUNDINGS/CROSS SECTIONS SHOW INVERSION HEIGHTS AND MOISTURE DEPTH
DROPPING ON WEDNESDAY/THURSDAY. WITH THIS DRY CONVECTIVE PATTERN...
CLOUDS AND SHOWERS WILL BE GREATEST DURING THE AFTERNOON AND EARLY
EVENING...WITH CLEARING OVERNIGHT AND DURING THE MORNING. THE DRY
AIRMASS AND LOW INVERSION WILL LIMIT SHOWER COVERAGE AND RAINFALL
AMOUNTS. SHOWERS MAY BE MORE ACTIVE NEAR THE BIG ISLAND...WHERE THE
12Z GFS SHOWS MOISTURE TO BE SLOWER TO DIMINISH.

LATE IN THE WEEK...AN UPPER LEVEL TROUGH WILL DIG NORTHEAST OF THE
STATE. THE 12Z GFS AND ECMWF ARE IN BETTER AGREEMENT WITH THE
LOCATION OF THIS TROUGH...WITH THE GFS TRENDING COOLER AND ECMWF
TRENDING WARMER WITH 500MB TEMPERATURES OVER THE ISLANDS. WHILE THE
BULK OF THE UPPER LEVEL ENERGY WILL PASS NORTHEAST OF THE STATE...
THIS SYSTEM WILL STILL PROPEL THE COLD FRONT SOUTHWARD ACROSS US.
THE ECMWF IS FASTER THAN THE GFS...AND ALSO QUICKER TO WEAKEN THE
FRONT. MODEL CROSS SECTIONS OVER THE ISLANDS SHOW AN INCREASE IN
MOISTURE DEPTH FRIDAY NIGHT OVER KAUAI...WITH A DIMINISHING TREND AS
IT MOVES FARTHER EAST ACROSS THE STATE. NORTH TO NORTHEAST WINDS
WILL FILL IN BEHIND THE FRONT OVER THE WEEKEND...AS A NEW HIGH
BUILDS NORTH OF THE AREA. BOTH GFS/ECMWF SHOW THIS HIGH BEING WEAKER
THAN THE LAST COUPLE...WITH RELATIVELY LIGHT TRADES EXPECTED FOR THE
FIRST HALF OF NEXT WEEK.

&&

.AVIATION...
A RATHER STABLE TRADE WIND FLOW WILL PERSIST THROUGH TONIGHT WITH A
DECREASE IN SPEED EXPECTED DURING THE DAY ON WEDNESDAY. LOW
LEVEL MOISTURE IN THE TRADE WINDS WILL CONTINUE TO BE GREATER OVER
THE SOUTHERN END OF THE STATE...GIVING HIGHER CHANCES FOR MOUNTAIN
OBSCURATION OVER WINDWARD BIG ISLAND AND MAUI SLOPES TONIGHT.
ELSEWHERE...VFR CONDITIONS WILL PREVAIL WITH ONLY ISOLATED AREAS OF
MVFR CIGS ACROSS WINDWARD TERRAIN.

THERE IS AN INVERSION AROUND 6000 TO 7000 FT...WITH WINDS BELOW
MAINLY IN THE 15 TO 20 KT RANGE ACCORDING TO RADAR VAD. CONDITIONS
FOR LOW LEVEL TURBULENCE TO THE LEE OF ISLAND TERRAIN WILL CONTINUE
TO BE BORDER LINE TONIGHT...WITH LOW LEVEL TURBULENCE CHANCES
DIMINISHING TOMORROW.

&&

.MARINE...
THE MORNING ASCAT PASS SHOWED A SOLID AREA OF 25 KNOTS THROUGH
ALENUIHAHA CHANNEL...WITH A COUPLE 25 KNOTS NEAR SOUTH POINT AS
WELL. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE TYPICALLY WINDIER
WATERS NEAR MAUI AND THE BIG ISLAND. WITH HIGH-RESOLUTION GUIDANCE
SHOWING WINDS CONTINUING THROUGH THE EVENING BEFORE DIMINISHING...
WILL KEEP THE ADVISORY GOING THROUGH THE NIGHT.

A SERIES OF SOUTH SWELLS WILL AFFECT THE STATE THROUGH THE
WEEKEND...WITH THE FIRST TO ARRIVE LATE TONIGHT. THE AMERICAN SAMOA
BUOY PICKED UP ON THIS SWELL THIS PAST WEEKEND...AND SEAS HAVE
REMAINED ELEVATED SINCE. A REINFORCEMENT IS EXPECTED LOCALLY ON
SATURDAY...WITH HIGHER VALUES POSSIBLE SUNDAY INTO MONDAY. SURF IS
EXPECTED TO REMAIN BELOW ADVISORY LEVELS WITH THESE SWELLS. A SERIES
OF SMALL NORTHWEST SWELLS WILL ALSO CONTINUE THROUGH EARLY NEXT
WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST WEDNESDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

DISCUSSION/MARINE...BRAVENDER
AVIATION...WROE