180 
FXHW60 PHFO 151330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON JUL 15 2013

.SYNOPSIS...
LIGHT EAST TO SOUTHEAST WINDS WILL BECOME MORE EASTERLY AND INCREASE 
SLIGHTLY THROUGH THE WEEK. SHOWERS ALSO WILL BECOME HEAVIER ACROSS 
MUCH OF THE STATE AROUND TUESDAY...AND THEN AGAIN OVER THE WEEKEND.

&&

.DISCUSSION...
SURFACE OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS REPORTED LIGHT 
WINDS WITH A BIT OF A SOUTH VECTOR COMPONENT ACROSS MOST OF THE 
STATE...AND SOUNDING DATA SHOWED THIS COMPONENT PRESENT THROUGH THE 
DEPTH OF SURFACE MIXED LAYER. SURFACE SPEEDS REMAINED HIGHER IN THE 
ALENUIHAHA CHANNEL. PRESSURE TRENDS WERE MIXED...SUGGESTING LITTLE 
CHANGE THROUGH THE SHORT RUN.

ALTHOUGH THE AIR MASS WAS ON THE DRY SIDE OF AVERAGE FOR THE 
SEASON...IT HAD MOISTENED SLIGHTLY OVERNIGHT...AND SATELLITE 
ESTIMATES OF PRECIPITABLE WATER SHOWED THE AIR MASS UPWIND HOLDING 
CLOSE-TO-TYPICAL AMOUNTS OF WATER VAPOR. RADAR DATA ALSO REPORTED 
CONSIDERABLE SHOWER ACTIVITY. EXISTING POPS WERE ADEQUATE FOR MOST 
WINDWARD ZONES...BUT PERSISTENT SHOWERS ALONG WEST SHORES OF THE BIG 
ISLAND REQUIRED A BOOST. QPF ALSO HAS BEEN INCREASED ACROSS THE 
STATE.

ALOFT...A LARGE LOW SPRAWLED TO THE NORTHWEST OF THE STATE...AND A 
WEAKER HIGH TO THE EAST...BUT THE LOCAL GRADIENT WAS NEARLY FLAT. 
GUIDANCE PREDICTED THIS INDIFFERENT CONDITION TO PERSIST THROUGH 
MUCH OF THE FORECAST PERIOD...AS A SERIES OF RETROGRADING LOWS PASS 
BY TO THE NORTH OF THE ISLANDS...BUT PRODUCE LITTLE NET CHANGE AT 
MID-LEVELS OVERHEAD.

THE SUBTROPICAL RIDGE AT THE SURFACE TO THE NORTH WILL REBUILD 
SOMEWHAT FROM ITS CURRENT MINIMUM...BUT ALL THE COMMOTION OVER IT 
WILL KEEP IT FROM STRENGTHENING MUCH. THUS...MODEST TRADE WINDS WILL 
RETURN...AND THEN PREVAIL.

GUIDANCE BROADLY SUPPORTED THE ARRIVAL OF A SLIGHTLY MOISTER AIR 
MASS AROUND TUESDAY...AND THEN AGAIN FROM FRIDAY INTO THE WEEKEND... 
BUT BY EARLY NEXT WEEK THE GREATEST CONCENTRATIONS OF WATER VAPOR 
SHOULD BECOME LIMITED TO AROUND THE BIG ISLAND. CURRENT CONDITIONS 
DESPITE THE DRY AIR MASS SUGGEST THAT...CONTRARY TO EARLIER 
PHILOSOPHY...EACH OF THE NEW MOISTURE FLUXES COULD AFFECT MORE THAN 
JUST THE USUAL WINDWARD SLOPES. TYPICALLY PREFERRED AREAS LIKELY 
WILL REMAIN FAVORED...MEANING THAT ONCE AGAIN THE BIGGEST CHANGE 
FROM USUAL CONDITIONS WILL BE NOT SO MUCH IN RAINFALL 
DISTRIBUTION...BUT IN AMOUNTS. THUS...QPF ALSO HAS BEEN INCREASED 
THROUGH THE MIDDLE AND END OF THE FORECAST PERIOD. IF MODEL TRENDS 
CONTINUE...THEN POPS MAY NEED A BOOST STATEWIDE AS WELL.

&&

.MARINE...
SMALL SOUTH SWELLS WILL CONTINUE TODAY...BUT A MODERATE SOUTH SWELL 
WILL BUMP UP THE SURF TUESDAY WITH SURF APPROACHING ADVISORY LEVELS 
ON WEDNESDAY AS THE SWELL PEAKS.

A SMALL CRAFT ADVISORY IS UP FOR THE ALENUIHAHA CHANNEL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR ALENUIHAHA 
CHANNEL.

&&

$$

RYSHKO