FNUS70 PHFO 181710
FWSHFO

SPOT FORECAST FOR PRESIDENTS DAY
NATIONAL WEATHER SERVICE HONOLULU HI
710 AM HST SAT APR 18 2009

IF CONDITIONS BECOME UNREPRESENTATIVE...PLEASE CONTACT
THE NATIONAL WEATHER SERVICE.

.DISCUSSION...LIGHT WINDS WILL PREVAIL ON THE LARGE SCALE
THROUGH THE FORECAST PERIOD...ALLOWING ISLAND SCALE WINDS
TO DOMINATE THE FLOW. THIS MEANS THAT LOW-LEVEL WINDS WILL
BE DOWNSLOPE IN THE NIGHTS AND MORNINGS...AND UPSLOPE DURING
THE AFTERNOONS AND EVENINGS. EMISSIONS WILL TEND TO MOVE UPSLOPE
AND POOL ALONG THE SLOPES IN THE AFTERNOONS AND EVENINGS...
AND THEN MOVE BACK DOWNSLOPE IN THE OVERNIGHT...LIKELY AFFECTING
MANY POPULATED AREAS IN EAST HAWAII. IN ADDITION...EMISSIONS WILL
LIKELY BE TRAPPED IN A LAYER CLOSE TO THE GROUND IN THE LATE NIGHTS
AND EARLY MORNINGS...WITH EMISSIONS IN THIS LAYER BECOMING LESS
CONCENTRATED BY MID TO LATE MORNING AS ISLAND HEATING INCREASES
VERTICAL MIXING. TRADE WINDS ARE NOT EXPECTED TO RETURN TO THE
BIG ISLAND UNTIL WEDNESDAY.

.TODAY...
SKY/WEATHER.........SUNNY UNTIL NOON...THEN MOSTLY CLOUDY.
                    CHANCE OF SHOWERS AFTER NOON.
MAX TEMPERATURE.....AROUND 66.
MIN HUMIDITY........75 PERCENT.
20-FOOT WINDS.......NORTH AROUND 5 MPH UNTIL 10 AM...THEN EAST.
MIXING HEIGHT.......4000 FT AGL.
TRANSPORT WINDS.....SOUTHWEST AROUND 5 MPH SHIFTING TO THE EAST IN
                    THE AFTERNOON.

.TONIGHT...
SKY/WEATHER.........MOSTLY CLOUDY UNTIL MIDNIGHT...THEN MOSTLY CLEAR.
                    CHANCE OF EVENING SHOWERS.
MIN TEMPERATURE.....AROUND 51.
MAX HUMIDITY........100 PERCENT.
20-FOOT WINDS.......SOUTHEAST AROUND 5 MPH UNTIL 10 PM...THEN LIGHT
                    AND VARIABLE.
MIXING HEIGHT.......4000 FT AGL.
TRANSPORT WINDS.....SOUTHWEST AROUND 5 MPH.

.SUNDAY...
SKY/WEATHER.........PARTLY SUNNY. SCATTERED SHOWERS AFTER NOON.
MAX TEMPERATURE.....AROUND 66.
MIN HUMIDITY........75 PERCENT.
20-FOOT WINDS.......NORTH AROUND 5 MPH UNTIL 10 AM...THEN
                    SOUTHEAST.
MIXING HEIGHT.......4000 FT AGL.
TRANSPORT WINDS.....VARIABLE LESS THAN 10 MPH.


FORECASTER...BIRCHARD

$$

REQUESTED BY...NPS
REASON FOR REQUEST...VOLCANIC EMISSIONS