847 
FXHW60 PHFO 231412 CCA
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SAT MAR 23 2013

.SYNOPSIS...
CLOUDS AND SHOWERS ASSOCIATED WITH A WEAK FRONTAL BOUNDARY OVER MAUI 
COUNTY WILL CONTINUE TO AFFECT MOST OF THE STATE THIS WEEKEND. THE 
FRONT WILL STALL AND TRANSITION TO A TROUGH THAT WILL LINGER IN THE 
VICINITY OF THE CENTRAL ISLANDS INTO EARLY NEXT WEEK. THE REMNANT 
MOISTURE ASSOCIATED WITH THIS FEATURE WILL REMAIN ACROSS THE 
STATE...BRINGING WET WEATHER...ESPECIALLY ACROSS PORTIONS OF THE 
WESTERN ISLANDS...FOR THE NEXT SEVERAL DAYS.

&&

.DISCUSSION...
A SHALLOW NORTH NORTHEAST TO SOUTH SOUTHWEST ORIENTED FRONTAL 
BOUNDARY HAS MOVED ACROSS WESTERN AND CENTRAL MOLOKAI OVERNIGHT 
BASED ON SURFACE OBSERVATIONS...THE VAD WIND PROFILE FROM THE 
MOLOKAI RADAR AND SATELLITE BASED SCATTEROMETER OBSERVATIONS. THE 
FRONT APPEARS TO BE NEAR EASTERN MOLOKAI AND LANAI AROUND 300 AM HST 
THIS MORNING. ELSEWHERE...A 1026 MB SURFACE HIGH IS LOCATED FAR WEST 
NORTHWEST OF KAUAI. THE ROUNDED EASTERN END OF A SURFACE RIDGE 
EXTENDS FROM THIS HIGH THROUGH A POINT ABOUT 200 MILES NORTH OF 
KAUAI. AS A RESULT...THE LOW-LEVEL FLOW OVER KAUAI AND OAHU IS FROM 
THE NORTHEAST. EAST OF THE FRONT...THE WINDS REMAIN LIGHT AND ARE 
GENERALLY FROM A SOUTH TO SOUTHEAST DIRECTION. WATER VAPOR IMAGERY 
SHOWS THE AXIS OF THE UPPER LEVEL TROUGH...WHICH WAS SUPPORTING THIS 
FRONT HAS SHIFTED FAR NORTH NORTHEAST OF THE ISLANDS. WITH THE LOSS 
OF THIS UPPER LEVEL SUPPORT...ALONG WITH THE FACT THERE IS 
NORTHEASTERLY FLOW WEST OF THE FRONT AND SOUTHEASTERLY FLOW TO THE 
EAST...IT APPEARS THE FRONTAL BOUNDARY IS ALREADY BEGINNING TO 
TRANSITION INTO A SURFACE TROUGH.

ANOTHER UPPER LEVEL TROUGH IS LOCATED FAR WEST OF KAUAI. SATELLITE 
IMAGERY SHOWS BROKEN TO OVERCAST CIRRUS CLOUDS OVER MOST OF THE 
ISLAND CHAIN. THESE HIGH CLOUDS ARE OBSCURING MOST OF THE LOW CLOUDS 
BELOW IN INFRARED SATELLITE IMAGERY. THE HIGH CLOUDS...WHICH CONSIST 
MAINLY OF ICE CRYSTALS...ARE BEING TRANSPORTED BY AN UPPER LEVEL 
SUBTROPICAL JET STREAM THAT IS ALONG THE EAST FLANK OF THE SECOND 
UPPER LEVEL TROUGH LOCATED FAR WEST OF KAUAI. RADAR REFLECTIVITY 
DATA SHOWS SHOWERS WITH LIGHT TO MODERATE RAINFALL ALONG THE 
FRONTAL BAND IN THE VICINITY OF LANAI...EASTERN MOLOKAI AND WEST 
MAUI. ADDITIONAL LIGHT TO MODERATE SHOWERS ARE OVER THE KAIWI 
CHANNEL AND JUST WEST OF THE LEEWARD BIG ISLAND COAST. ISOLATED 
LIGHT SHOWERS ARE IN THE VICINITY OF OAHU AND THE SOUTHEASTERN BIG 
ISLAND COAST,

MOISTURE ASSOCIATED WITH THE FRONTAL BOUNDARY WILL REMAIN IN THE 
VICINITY OF THE ALOHA STATE...PROVIDING LOW CLOUDS AND SHOWERS. THE 
SATELLITE DERIVED PRECIPITABLE WATER VALUES OVER THE CENTRAL ISLANDS 
ARE ESTIMATED TO BE ABOUT 1.4 INCHES...WITH LESSER VALUES TOWARD 
KAUAI. THE PRESENCE OF THE WEAK SURFACE FRONT IS ALSO KEEPING THE 
SURFACE PRESSURE GRADIENT FAIRLY WEAK OVER THE REGION. THEREFORE... 
SURFACE WINDS ARE EXPECTED TO REMAIN ON THE LIGHTER SIDE...EXCEPT 
FOR KAUAI AND OAHU WHICH WILL EXPERIENCE SLIGHTLY STRONGER 
NORTHEASTERLY FLOW FOR THE NEXT 24 TO 30 HOURS TO THE WEST OF THE 
FRONT / TROUGH. 

THE TROUGH IS EXPECTED TO LINGER ACROSS THE ISLANDS INTO EARLY NEXT 
WEEK. FORECAST MODELS INDICATE UPPER LEVEL SHORT WAVES WILL ALSO 
MOVE ACROSS THE ISLANDS DURING THE NEXT FEW DAYS. THE PASSAGE OF 
THESE UPPER LEVEL FEATURES IS EXPECTED TO PRODUCE A SLIGHT 
DESTABILIZATION OF THE AIR MASS OVER THE REGION. WITH THE LINGERING 
MOISTURE IN THE VICINITY OF THE ISLANDS...THE STATE WILL LIKELY HAVE 
MORE WIDESPREAD LOW CLOUDS AND SHOWERS. THE PRESENCE OF THE TROUGH 
WILL ALSO LIKELY KEEP WINDS RELATIVELY LIGHT. THE SUBTROPICAL JET 
STREAM WILL ALSO PERSIST AT THE UPPER LEVELS ABOVE THE STATE...WHICH 
WILL CONTINUE TO BRING HIGH CLOUDS ACROSS THE REGION...KEEPING SKIES 
SOMEWHAT CLOUDY FROM THIS WEEKEND INTO EARLY NEXT WEEK.

TRADE WINDS MAY FINALLY RETURN TO THE ISLANDS TOWARDS THE MIDDLE OF 
NEXT WEEK...AS THE SURFACE TROUGH EVENTUALLY DISSIPATES...AND 
SURFACE HIGH PRESSURE BUILDS FAR NORTH OF THE ISLANDS. SHOWERS 
CARRIED BY THE TRADES WILL MAINLY AFFECT WINDWARD AND MAUKA SECTIONS 
OF THE ISLANDS.

&&

.AVIATION...
MOISTURE IN THE FORM OF LOW CLOUDS AND SHOWERS ASSOCIATED WITH A 
WEAKENING FRONT OVER THE CENTRAL ISLANDS WILL PRODUCE AREAS OF 
MVFR...AND ISOLATED IFR CONDITIONS...ESPECIALLY OVER PORTIONS OF 
MAUI COUNTY EARLY THIS MORNING. AN AIRMET FOR MOUNTAIN OBSCURATION 
IS CURRENTLY IN EFFECT FOR THE HIGHER TERRAIN ON MAUI...LANAI... 
MOLOKAI...OAHU AND KAUAI. THESE CONDITIONS MAY PERSIST THROUGH THIS 
AFTERNOON AS THE FRONT TRANSITIONS TO A SURFACE TROUGH...WHICH IS 
EXPECTED TO STALL OVER THE CENTRAL ISLANDS LATER TODAY.

&&

.MARINE...
THE CURRENT NORTHWEST SWELL CONTINUES TO SUBSIDE EARLY THIS 
MORNING...WITH THE SIGNIFICANT WAVE HEIGHT AT THE WAIMEA BAY BUOY 
DOWN TO 6 FEET WITH A PERIOD OF 13 SECONDS. A LONG PERIOD NORTHWEST 
SWELL ARRIVING LATE SUNDAY WILL PRODUCE MODERATE SURF HEIGHTS ALONG 
NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS...WHICH WILL 
PEAK BELOW THE HIGH SURF ADVISORY CRITERIA ON MONDAY. THIS SWELL 
WILL GRADUALLY SUBSIDE FROM TUESDAY THROUGH WEDNESDAY. SMALL SOUTH 
SWELLS WILL MAINTAIN BACKGROUND SURF ALONG SOUTH FACING SHORES 
THROUGH THE MIDDLE OF NEXT WEEK.

NO SMALL CRAFT ADVISORY CONDITIONS ARE FORECAST FOR THE HAWAIIAN 
COASTAL WATERS INTO THE MIDDLE OF NEXT WEEK.

&&

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

&&

$$

HOUSTON