Flash Flood Warning 14, NWS Honolulu, HI

974 
WGHW70 PHFO 140901
FFSHFO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
1101 PM HST SUN JUL 13 2014

HIC001-140910-
/O.CAN.PHFO.FF.W.0014.000000T0000Z-140714T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
HAWAII HI-
1101 PM HST SUN JUL 13 2014

...THE FLASH FLOOD WARNING IS CANCELLED FOR THE ISLAND OF HAWAII IN
HAWAII COUNTY...

WEATHER RADAR SHOWED THAT HEAVY RAINFALL HAS MOVED OFFSHORE. THUS THE
FLASH FLOOD WARNING IS CANCELLED. RUNOFF WILL REMAIN HIGHER THAN 
USUAL IN STREAM BEDS AND LOW-LYING AREAS FOR SEVERAL HOURS.

LAT...LON 1956 15543 1954 15523 1921 15514 1889 15574

$$

RYSHKO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN JUL 13 2014

.SYNOPSIS...
A TROUGH PASSING SOUTH OF THE STATE WILL SPREAD A VERY MOIST AIR
MASS NORTHWEST FROM THE BIG ISLAND...ENCOURAGING THE DEVELOPMENT OF
LOCALLY HEAVY SHOWERS THROUGH TUESDAY. MEANWHILE...TRADE WINDS WILL
PERSIST THROUGH THE FORECAST PERIOD...STRENGTHENING TONIGHT...
WEAKENING THROUGH THE FIRST HALF OF THE WEEK...AND THEN
STRENGTHENING AGAIN FROM WEDNESDAY INTO FRIDAY.

&&

.DISCUSSION...
A TROUGH PASSING SOUTH OF THE BIG ISLAND BROUGHT WITH IT A MOIST AIR
MASS FROM THE DEEP TROPICS...ENCOURAGING HEAVY SHOWERS AND
THUNDERSTORMS TO DEVELOP ALONG NORTHEAST AND SOUTHEAST SLOPES OF THE
BIG ISLAND FROM THIS AFTERNOON INTO TONIGHT. THIS AIR MASS LIKELY
WILL SPREAD FURTHER NORTHWEST ONTO PARTS OF MAUI COUNTY OVERNIGHT. A
DRIER AIR MASS WILL PREVAIL FROM MOLOKAI TO NIIHAU THROUGH THE SHORT
RUN...BUT THE DEEPER MOISTURE WILL REACH MOST OF THE STATE BY
TUESDAY. THE PASSING TROUGH ALSO WILL TIGHTEN THE PRESSURE GRADIENT
ACROSS THE STATE...LEADING TO LOCALLY STRONGER TRADE WINDS THROUGH
THE NEXT 24 TO 36 HOURS.

INTERESTINGLY...THE CONVECTION WAS DRIVEN ALMOST EXCLUSIVELY BY THE
PLENTIFUL MOISTURE FROM LOWER LEVELS. ALOFT...MODERATE RIDGING
EXTENDED OVER THE AREA FROM THE EAST...AND GUIDANCE GENERALLY AGREED
IN PREDICTING THE RIDGE TO BUILD GRADUALLY THROUGH ABOUT TUESDAY.
LIKEWISE...TEMPERATURES ALOFT WERE WARMER THAN THE USUAL -10 CELSIUS
THRESHOLD FOR SIGNIFICANT RISK OF THUNDER. AS A RESULT...LOCAL TOOLS
RUN ON MODEL OUTPUT ALSO UNDER-PREDICTED THE CHANCE OF THUNDER FOR
THE BIG ISLAND THIS EVENING...AND MAY DO SO AGAIN FOR THE REST OF
THE STATE DURING THE NEXT COUPLE OF DAYS. THAT SAID...THE GREATEST
CONVERGENCE AT THE SURFACE SHOULD REMAIN CLOSE TO THE TROUGH
AXIS...LIMITING THE LIKELIHOOD OF DEEP CONVECTION OVER THE SMALLER
ISLANDS.

BY THE SECOND HALF OF THE WEEK...RIDGING ALOFT SHOULD BUILD EVEN
FURTHER...SUPPORTING SLIGHTLY STRONGER TRADE WINDS NEAR THE SURFACE.
THE WINDS WILL CLEAR OUT MOST OF THE LINGERING MOISTURE IN TURN...
THOUGH SOME WILL END UP ENHANCING SHOWERS OVER WINDWARD SLOPES.

&&

.AVIATION...
MOISTURE FROM A SURFACE TROUGH MOVING THROUGH THE AREA WILL MAINLY
AFFECT WINDWARD PARTS OF THE BIG ISLAND TONIGHT...AND EVENTUALLY THE
OTHER ISLES TONIGHT AND TOMORROW AS IT MOVES WEST.  PERIODS OF MVFR
AND IFR CONDITIONS WILL OCCUR...ESPECIALLY IN WINDWARD AND MAUKA
SECTIONS. AIRMETS FOR MOUNTAIN OBSCURATION HAVE ALREADY BEEN ISSUED
FOR THE BIG ISLAND...MAUI AND MOLOKAI.  LANAI...OAHU AND KAUAI WILL
BE ADDED LATER IF NECESSARY.

ISOLATED THUNDERSTORMS HAVE ALSO BEEN FIRING OVER WINDWARD AREAS OF
THE BIG ISLAND...AND THE CHANCE FOR MORE WILL GRADUALLY DIMINISH AS
THE NIGHT WEARS ON.

&&

.MARINE...
THE TROUGH PASSING JUST TO THE SOUTH WILL KEEP THE PRESSURE GRADIENT
STRONG ENOUGH TO REQUIRE A SMALL CRAFT ADVISORY THROUGH TONIGHT. AS
THE TROUGH MOVES WEST OF THE BIG ISLAND INTO MONDAY MORNING...THE
GRADIENT SHOULD RELAX ENOUGH SO THAT WINDS DROP BELOW THE 25-KNOT
ADVISORY THRESHOLD. ANY DECREASE IN WINDS WILL BE BRIEF THOUGH...AS
BUILDING HIGH PRESSURE FAR NORTHEAST OF THE STATE LIKELY WILL
STRENGTHEN WINDS ENOUGH TO REQUIRE A SMALL CRAFT ADVISORY AGAIN BY
THE SECOND HALF OF THE WEEK.

A SOUTH SWELL WILL BRING INCREASED SURF TO SOUTH-FACING SHORES
THROUGH TUESDAY...POSSIBLY RAISING IT TO NEAR THE ADVISORY LEVEL.
ANOTHER SOUTH SWELL WILL ARRIVE AROUND WEDNESDAY...SUPPORTING
MODERATE SURF ALONG SOUTH-FACING SHORES INTO NEXT WEEKEND.

&&

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

&&

AVIATION...KINEL
REST...RYSHKO