Heavy Rain in Hawaii, June 10, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST WED JUN 10 2015

.SYNOPSIS...
TRADE WINDS WILL GRADUALLY DIMINISH OVER THE NEXT FEW DAYS AS A
SURFACE TROUGH PASSES NORTH OF THE STATE. LOCALIZED SEA BREEZES WILL
BECOME MORE WIDESPREAD OVER THE WEEKEND. CLOUDS AND SHOWERS WILL BE
FOCUSED PRIMARILY OVER WINDWARD AND MAUKA AREAS MAINLY AT NIGHT AND
DURING THE MORNING FOR THE NEXT COUPLE DAYS...THEN BEGIN TO DEVELOP
OVER INTERIOR AND LEEWARD AREAS DURING THE AFTERNOON AND EVENING BY
THE WEEKEND.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL LOW NORTHEAST OF THE STATE.
THIS LOW IS GRADUALLY MOVING SOUTHWESTWARD. ANOTHER TROUGH IS
LOCATED FAR TO THE NORTHWEST...WITH A HIGH TO OUR NORTHWEST. AT THE
SURFACE...HIGH PRESSURE IS LOCATED FAR TO THE NORTH-NORTHEAST...WITH
SURFACE TROUGHS TO THE NORTHWEST AND TO THE EAST OF THE STATE. 12Z
SOUNDINGS FROM LIHUE AND HILO SHOW INVERSIONS OF 8-10KFT AND
PRECIPITABLE WATERS JUST OVER 1.3 INCHES. EARLY MORNING MIMIC TOTAL
PRECIPITABLE WATER IMAGERY SHOWS POCKETS OF SIMILAR MOISTURE
EXTENDING SEVERAL HUNDRED MILES UPSTREAM TO THE NORTHEAST.

THE UPPER LEVEL LOW NORTHEAST OF THE STATE IS EXPECTED TO MOVE NORTH
AND WEAKEN...BECOMING ABSORBED INTO THE DIGGING UPPER TROUGH THAT
CUTS OFF WELL NORTH OF THE STATE. AS THIS OCCURS...SUBSIDENCE
ASSOCIATED WITH BUILDING MID-LEVEL HEIGHTS WILL HELP TO STRENGTHEN
AND LOWER THE INVERSION. FORECAST SOUNDINGS/CROSS SECTIONS SHOW THE
CURRENT ELEVATED INVERSION STRENGTHENING FROM THURSDAY INTO
FRIDAY...THOUGH WITH MOISTURE DEPTH DIMINISHING MORE RAPIDLY BY
TONIGHT. RAINFALL AMOUNTS HAVE BEEN HIGHER OVER KAUAI/BIG
ISLAND...WITH A THIRD TO A HALF INCH IN THE PAST 12 HOURS COMPARED
TO LESS THAN A TENTH OF AN INCH ELSEWHERE. THIS MATCHES UP WITH THE
POCKETS OF GREATER MOISTURE SEEN IN THE MIMIC IMAGERY. A MULTI-MODEL
BLEND OF PRECIPITABLE WATER FIELDS SHOWS A DOWNWARD TREND FROM LATE
THURSDAY THROUGH FRIDAY...WITH BELOW NORMAL MOISTURE VALUES HEADING
INTO THE WEEKEND.

12Z MODELS SHOW THE HIGH WILL SHIFT NORTHWARD AND ACTUALLY
STRENGTHEN THROUGH THE WEEKEND. HOWEVER...THE SURFACE TROUGH TO OUR
EAST WILL SHIFT NORTHWEST AND PASS BETWEEN US AND THE HIGH...KEEPING
THE GRADIENT LIGHT ACROSS THE ISLANDS. INITIALLY THE GRADIENT WILL
WEAKEN SLIGHTLY OVER THE NEXT COUPLE DAYS...THEN FURTHER DIMINISH
OVER THE WEEKEND AS A WEAK LOW DEVELOPS NORTH OF THE AREA ALONG THE
TROUGH. MODERATE TRADE WINDS WILL GIVE WAY TO LOCALIZED SEA BREEZES
LATE IN THE WEEK...THEN MORE WIDESPREAD SEA BREEZES OVER THE
WEEKEND. IT APPEARS THAT THERE SHOULD REMAIN ENOUGH OF A BACKGROUND
GRADIENT TO KEEP SOME SHOWERS FOCUSED ACROSS WINDWARD SECTIONS AT
NIGHT...WITH THE BULK OF THE CLOUDS AND SHOWERS OCCURRING ACROSS
INTERIOR AND LEEWARD SECTIONS DURING THE AFTERNOON AND EVENING. THE
DRIER AND MORE STABLE AIRMASS WILL LIMIT RAINFALL AMOUNTS.

&&

.AVIATION...
MODERATE TO LOCALLY BREEZY TRADE WINDS SHOULD START TO DIMINISH
INTO TONIGHT AS A SURFACE TROUGH EAST OF THE STATE MOVES CLOSER AND
BECOMES MORE PRONOUNCED. HOWEVER...AT THIS TIME WINDS REMAIN CLOSE
TO THE THRESHOLD FOR LOW LEVEL TURB AND AIRMET TANGO HAS JUST BEEN
ISSUED. ALTHOUGH...THERE HAVE NOT BEEN ANY REPORTS OF TURB THIS
MORNING...VAD WIND PROFILES SHOW WINDS BETWEEN 15 AND 20 KT THROUGH
THE LAYER. MORNING AMDAR REPORTS SHOW THE MAIN LOW LEVEL INVERSION
NEAR 10 THOUSAND FEET AND A WEAK SECONDARY INVERSION AROUND 5
THOUSAND FEET. AMDARS SHOW WINDS AT THIS LEVEL NEARING 25 KT...
SUGGESTING MOST SIGNIFICANT TURB WILL BE 5 THOUSAND FEET AND BELOW.
AIRMET TANGO FOR LOW LEVEL TURB IS LIKELY TO BE CANCELLED BY THIS
EVENING.

OTHERWISE...CLOUDS AND SHOWERS WILL FOCUS ALONG WINDWARD AND
MOUNTAIN AREAS. MOST WINDWARD ACTIVITY IS EXPECTED ALONG MAUI AND
BIG ISLAND SLOPES. SOME SHOWERS WILL CARRY PASSING PERIODS MVFR CIGS
AND VIS...ELSEWHERE VFR WILL PREVAIL.

&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE TYPICALLY WINDIER
AREAS NEAR MAUI AND THE BIG ISLAND. THIS ADVISORY ENDS BY
TONIGHT...WHICH MATCHES THE LATEST HIGH RESOLUTION WRF GUIDANCE FROM
UH.

WAVEWATCH GUIDANCE SHOWS A SMALL EASTERLY SWELL FROM FORMER BLANCA
REACHING US TONIGHT. SO FAR THE WINDWARD BUOYS NEAR THE ISLANDS HAVE
NOT PICKED UP ON THIS LONGER PERIOD ENERGY.

&&

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

&&

DISCUSSION/MARINE...BRAVENDER
AVIATION...EATON