Area Forecast Discussion
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000
FXPQ60 PGUM 272204
AFDPQ

AREA FORECAST DISCUSSION...RESENT
NATIONAL WEATHER SERVICE TIYAN GU
749 AM CHST SAT FEB 28 2015

.SYNOPSIS...NORTHEAST WINDS AND A FEW SMALL SHOWERS PREVAIL
ACROSS THE MARIANAS THIS MORNING. RELATIVELY DRY WEATHER IS
EXPECTED THROUGH THE WEEKEND AND INTO MONDAY.

&&

.DISCUSSION...
LITTLE CHANGE MADE TO THE FORECAST. 2 KFT WINDS ON THE VAD WERE
20 KNOTS AND SCATTEROMETER DATA SHOWED NORTHEAST WINDS BETWEEN 15
TO 20 KTS. THESE WIND SPEEDS ARE CONSISTENT WITH CURRENT MODEL
PREDICTIONS. WINDS OF 15 TO 20 MPH TODAY WILL DECREASE TO 10 TO 15
MPH TONIGHT. THE LIGHTER WINDS WILL PERSIST THROUGH MONDAY BEFORE
AN AREA OF HIGH PRESSURE BUILDS OUT INTO THE NORTHWEST PACIFIC AND
ELEVATES WIND SPEEDS.

RADAR IMAGERY THIS MORNING SHOWED ONLY A FEW SHOWERS MOVING ACROSS
THE LOCAL AREA. SATELLITE PRECIPITABLE WATER INDEX SHOWED A SLIGHTLY
HIGHER VALUE OVER THE MARIANAS COMPARED TO PREVIOUS DAYS. THIS
MAY LEAD TO A SLIGHTLY INCREASED CHANCE OF SHOWERS TODAY...BUT
STILL BELIEVE THAT A SLIGHT CHANCE OF SHOWERS MENTIONED IN TODAY`S
FORECAST SHOULD SUFFICE. MODEL PREDICTIONS KEEP DEEP LAYER
MOISTURE LACKING THROUGH THE FORECAST. GFS...ECMWF AND NAVGEM
PORTRAY A WEAK TROUGH MOVING ACROSS THE MARIANAS MONDAY THROUGH
TUESDAY. WHILE THESE FEATURES MAY PRODUCE A FEW MORE CLOUDS STILL
ONLY EXPECT ISOLATED SHOWERS TO PREVAIL BECAUSE OF THE LACK OF
DEEP MOISTURE.

&&

.MARINE...
OBSERVATIONS THIS MORNING FROM THE RITIDIAN AND IPAN BUOY INDICATED
SEAS AT AROUND 6 TO 7 FEET. A EAST AND NORTHEAST SWELL ARE PRESENT
ACROSS THE MARIANAS THIS MORNING. THE NORTHEAST SWELL WILL BE
REPLACED BY A NORTH SWELL MONDAY. THESE SWELLS WILL NOT BECOME
LARGE SO ONLY EXPECT A MODERATE RISK OF RIP CURRENTS ON NORTH AND
EAST FACING REEFS THROUGH THE FORECAST.

&&

.FIRE WEATHER...
FIRE WEATHER WATCH IS STILL OUT UNTIL SUNDAY AFTERNOON. WINDS MAY
BE HIGH ENOUGH AND RELATIVE HUMIDITY LOW ENOUGH THIS AFTERNOON TO
PRODUCE CONDITIONS FAVORABLE FOR ANOTHER RED FLAG WARNING. WINDS
MAY DECREASE ENOUGH SUNDAY SO THAT A RED FLAG WARNING MAY NOT
NECESSARY.

&&

.EASTERN MICRONESIA...
A FRESH TRADE-WIND SURGE IS PROGRESSING ACROSS MICRONESIA THIS
MORNING. ITS LEADING EDGE...IN THE FORM OF A TRADE DISTURBANCE IS
PASSING OVER CHUUK. SPORADIC DEEP CONVECTION ASSOCIATED WITH THIS
SYSTEM WILL PERSIST THERE THRU THIS EVENING. A TRADE CONVERGENT ZONE
RELATED TO THE SURGE CAN BE SEEN BETWEEN 3N AND 6N...MEANDERING
EASTWARD FROM THE DISTURBANCE ACROSS THE DATE LINE TO NEAR 165W.
SHOWERS AND POSSIBLE THUNDERSTORMS NEAR THIS ZONE WILL TRAIN ACROSS
KOSRAE THRU SUNDAY AFTERNOON. BEING JUST NORTH OF THE NORTHERN
EXTENT OF THE ZONE...SHOWER COVERAGE OVER POHNPEI SHOULD STAY AT
ISOLATED THRU THIS EVENING BUT CANNOT RULE OUT A THUNDERSTORM OR
TWO. BESIDES BEING NORTH OF THE CONVERGENT ZONE...LATEST SOUNDING
FROM MAJURO ALSO REVEALS MUCH DRIER AIR ABOVE 500MB. THIS WILL LOWER
THE CHANCE OF THUNDERSTORMS BUT A WEAK DISTURBANCE EMBEDDED ALONG
THE ZONE COULD STILL SQUEEZE OUT A FEW SHOWERS THERE THRU SUNDAY.

THE LARGE SUB-TROPICAL HIGH CURRENTLY NORTH OF WAKE ISLAND NEAR
35N170E WILL SLOWLY DRIFT EASTWARD ACROSS THE DATE LINE OVER THE
NEXT COUPLE OF DAYS. THIS SHOULD ALLOW TRADE WINDS TO EASE ACROSS
THE REGION. NEVERTHELESS RESIDUAL TRADE CONVERGENCE IS GOING TO
MAINTAIN ISOLATED THUNDERSTORMS NEAR CHUUK...POHNPEI AND KOSRAE
UNTIL MONDAY NIGHT. AS TRADE WINDS DECREASE FURTHER TOWARD
MIDWEEK...A DRIER TRADE REGIME WOULD SPREAD WESTWARD FROM MAJURO
INTO THE REST OF THE LOCALES.

LATEST READINGS FROM BOTH ALTIMETRY AND COMPUTER MODELS GUIDANCE
SUPPORT A FURTHER DECREASE ON THE NORTH-NORTHEAST SWELL NEAR CHUUK
AND POHNPEI. THIS HAS ALLOWED SURF HEIGHTS TO DROP BELOW ADVISORY
LEVELS THIS MORNING. ON ANOTHER HAND...LATEST ASCAT SATELLITE
IMAGERY INDICATES THE TRADE-WIND SURGE IS BECOMING MORE ROBUST WITH
20 TO 25-KNOT WINDS BETWEEN 6N AND 15N FROM 153E TO THE DATE LINE.
EAST-NORTHEAST WIND WAVES AND SWELL GENERATED BY THIS SURGE WILL
CAUSE SURF TO RISE ACROSS CHUUK...POHNPEI...KOSRAE STATES AND THE
MARSHALL ISLANDS TODAY AND TONIGHT. WITH A LOWER THRESHOLD OF 8
FEET...SURF IS EXPECTED TO REACH HAZARDOUS LEVELS ON KOSRAE BY NOON.
SURF HEIGHTS ON CHUUK...POHNPEI AND MAJURO SHOULD STAY BELOW
HAZARDOUS LEVELS OF 12 FEET BUT HIGHER RIP CURRENT RISK WILL BE
LIKELY. THERE IS ALSO A CHANCE FOR SEAS TO RISE BACK TO HAZARDOUS
LEVELS FOR SMALL CRAFT OPERATION ACROSS THE REGION LATER THIS
AFTERNOON OR EVENING. DAY SHIFT WILL NEED TO MONITOR SATELLITE
ALTIMETRY CLOSELY TODAY.

&&

.WESTERN MICRONESIA...
THE CHUUK FORECAST DISCUSSION IS INCLUDED WITH EASTERN MICRONESIA
ABOVE DUE TO A SIMILAR SYNOPTIC WEATHER PATTERN AS POHNPEI AND
KOSRAE.

A NEAR-EQUATORIAL TROUGH IS ANTICIPATED TO REMAIN NEAR 3N SOUTH OF
BOTH KOROR AND YAP FOR THE NEXT COUPLE OF DAYS. THEREFORE DRIER
MODERATE TRADES WILL PROVIDE FAIR WEATHER OVER THESE PLACES THRU
SUNDAY NIGHT. A DEVELOPING FRONTAL SYSTEM IS STILL FORECASTED TO
TRACK EAST-NORTHEASTWARD FROM SOUTHERN CHINA INTO SOUTHERN JAPAN BY
MONDAY OR TUESDAY. THIS MIGHT PROVOKE THE NEAR-EQUATORIAL TROUGH TO
LIFT NORTHWARD CLOSER TO KOROR AND YAP. EVEN SO...MOST OF THE SHOWER
ACTIVITY RELATED TO THE TROUGH SHOULD STAY NEAR KOROR AND SOUTH OF
YAP DURING THE FIRST HALF OF NEXT WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...FIRE WEATHER WATCH THROUGH SUNDAY AFTERNOON FOR GUZ001.

MARIANAS WATERS...NONE.
&&

$$

ZIOBRO/CHAN



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