Area Forecast Discussion
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420
FXPQ60 PGUM 052113
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
713 AM CHST FRI MAY 6 2016

.SYNOPSIS...
PGUA DOPPLER WEATHER RADAR SHOWS ISOLATED SHOWERS MOVING THROUGH
THE MARIANAS WATERS. THE VAD WIND PROFILE REVEALS EAST WINDS OF 12
TO 20 KNOTS THROUGH THE LOWEST 5 THOUSAND FEET OF THE AIR. THE
WEATHER BALLOON FROM THURSDAY MORNING SHOWS THE WINDS SWITCH TO
SOUTHWEST AT AROUND 25 THOUSAND FEET.

&&

.DISCUSSION...
MODELS...RADAR AND SATELLITE ALL SHOW LITTLE IN THE WAY OF
UPSTREAM ACTIVITY FOR THE MARIANAS OVER THE NEXT FEW DAYS AT
LEAST. SEAS WILL EDGE UP A FOOT FOR THE WEEKEND...THEN BACK DOWN.
WINDS WILL REMAIN EAST WITH LITTLE CHANGE THROUGH THE FORECAST
PERIOD.

&&

.FIRE WEATHER...
WINDS ARE EXPECTED TO REMAIN BELOW RED FLAG CRITERIA THROUGH THE
FORECAST PERIOD...ALTHOUGH THEY MIGHT COME CLOSE SATURDAY. THE
KEETCH-BYRAM DROUGHT INDEX IS UP TO 768 THOUGH...MATCHING ITS PEAK
EARLIER THIS YEAR. THAT MEANS WE ARE NOW ONCE AGAIN IN COMPETITION
WITH THE 2010 PEAK OF 779...WHICH HAPPENED IN JUNE.

&&

.CLIMATE...
ACCORDING TO MY SPREADSHEETS...THE ONLY WAY THE NORTHWEST PACIFIC
CAN STILL BE TROPICAL CYCLONE FREE AT THE END OF MAY...AS WE HAVE
A GOOD SHOT AT DOING THIS YEAR...IS IF LA NINA IS ON THE WAY. IT
CAN ONLY HAPPEN UNDER NEUTRAL BECOMING LA NINA WHICH IS NOT THIS
YEAR...OR EL NINO BECOMING LA NINA...WHICH IS ONE OF THE LIKELY
OUTCOMES. IN A FEW WEEKS WE MAY BE ABLE TO COMPLETELY RULE OUT EL
NINO OR EL NINO BECOMING NEUTRAL.

&&

.EASTERN MICRONESIA...
LATEST ASCAT SATELLITE STREAMLINE ANALYSIS REVEALS MODERATE TO
FRESH TRADE WINDS FROM CHUUK STATE EASTWARD TO THE MARSHALL
ISLANDS. A TRADE-WIND DISTURBANCE IS VISIBLE NEAR 160E...
APPROACHING KOSRAE AND POHNPEI THIS MORNING. EXPECT SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM TO REACH KOSRAE LATER
THIS MORNING...AND POHNPEI THIS EVENING. FARTHER WEST...DRIER
TRADES SHOULD MAINTAIN FAIR CONDITIONS NEAR CHUUK THRU SATURDAY
MORNING. BY SATURDAY EVENING... CONVECTION RELATED TO THE SAME
SYSTEM NEAR POHNPEI WILL ALSO SPREAD WESTWARD OVER CHUUK.
MEANWHILE...SURFACE RIDGING EAST OF THIS SAME DISTURBANCE WILL
PROVIDE FAIR WEATHER TO MAJURO UNTIL SATURDAY MORNING.

A TRADE-WIND CONVERGENCE ZONE BETWEEN 3N AND 8N IS MEANDERING
EASTWARD FROM NEAR 180 TO BEYOND 155W. THIS FEATURE IS ANTICIPATED
TO REACH THE MARSHALL ISLANDS BY SATURDAY NIGHT WITH ANOTHER ROUND
OF WET WEATHER FOR MAJURO. AS IT PROGRESSES FARTHER WESTWARD...IT
WILL ALSO PROLONG WETNESS FOR KOSRAE...POHNPEI AND CHUUK THRU
EARLY NEXT WEEK.

&&

.WESTERN MICRONESIA...
REASONING FOR THE CHUUK FORECAST CAN BE FOUND UNDER EASTERN
MICRONESIA ABOVE.

CONVERGING TRADE WINDS BETWEEN TWO TRADE-WIND DISTURBANCES...ONE
SOUTHWEST OF KOROR NEAR 130E AND ANOTHER ONE SOUTHEAST OF YAP AT
145E ARE TAKING ADVANTAGE OF MID-LEVEL MOISTURE AND DIVERGENT FLOW
ALOFT TO TRIGGER SPORADIC CONVECTION SOUTH OF KOROR AND YAP NEAR
6N. STRONG SUBSIDENCE ABOVE 700MB ASSOCIATED WITH AN UPPER-LEVEL
TROUGH OVER KOROR AND YAP SHOULD PREVENT THE BULK OF THIS
CONVECTION FROM SPREADING NORTHWARD AT LEAST THRU THIS EVENING.
AS THE UPPER TROUGH GRADUALLY DRIFTS WESTWARD AWAY FROM BOTH
LOCATIONS ON SATURDAY...AN ENVIRONMENT FAVORABLE FOR CONVECTION
WILL SHIFT NORTHWARD. AS A RESULT...EXPECT CONVECTION TO SPREAD
OVER KOROR NEAR NOON SATURDAY AND POSSIBLY OVER YAP ON SUNDAY.
PERIODIC HEAVIER SHOWERS PRODUCED BY THIS CONVECTION SHOULD
PROVIDE MORE RELIEF FROM THE CURRENT DROUGHT THRU EARLY NEXT
WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

STANKO/CHAN



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