035
FXPQ60 PGUM 020756
AFDPQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
556 PM CHST TUE APR 2 2019
MARIANAS SYNOPSIS
DRY CONDITIONS ARE SEEN ACROSS MUCH OF THE AREA EXCEPT FOR NEAR GUAM
WHERE SHOWERS HAVE CONTINUED TO DEVELOP NEARBY AND MOVED WESTWARD
THROUGH THE GUAM WATERS. A SURFACE TROUGH IS JUST WEST OF GUAM AND
EXTENDS SOUTHWARD TO A WEAK CIRCULATION NEAR 5N143E. WELL SE OF THE
MARIANAS IS ANOTHER CIRCULATION THAT IS CENTERED NEAR 5N156E. THIS
CIRCULATION IS SURROUNDED WITH ABUNDANT CLOUD COVER AND SHOWERS AND
MODELS HAVE DIFFERING OPINIONS ON WHAT ROLE, IF ANY, IT WILL PLAY IN
LOCAL WEATHER LATER THIS WEEK OR WEEKEND.
DISCUSSION
FOR THE SHORT-TERM, HAVE INCREASED GUAM SHOWERS TO SCATTERED, BUT
SHOWERS ARE EXPECTED TO GRADUALLY TAPER OFF BY MIDNIGHT. WED AND THU
LOOK TO BE DRIER, SIMILAR TO THE PAST COUPLE OF WEEKS. FOR LATE WEEK,
MODELS DIFFER IN HOW TO HANDLE THE CIRCULATION SW OF POHNPEI. GFS
CONTINUES TO BE AGGRESSIVE IN PUSHING IT NORTHWESTWARD TO THE EAST OF
THE MARIANAS, WHILE ECMWF KEEPS IT WEAKER AND FARTHER SOUTH ON A WNW
HEADING. AS WITH THE PAST COUPLE OF DAYS, CURRENT FORECAST PHILOSOPHY
SIDES WITH THE ECMWF. AS A RESULT, CLOUDIER SKIES AND A SMALL
INCREASE IN SHOWERS IS EXPECTED LATE WEEK AS THE DISTURBANCE PASSES
TO THE SOUTH. IN ADDITION, DEWPOINT GRIDS WERE REFRESHED WITH DATA
FROM THE ECMWF TO ELIMINATE THE HIGH DEWPOINTS EAST OF THE MARIANAS
ASSOCIATED WITH THE GFS DISTURBANCE. THIS WILL LIKELY LESSEN THE HEAT
INDEX CALCULATIONS FOR LATE WEEK. BUT WITH ALL THAT SAID, FUTURE
SHIFTS WILL HAVE TO CONTINUE TO WATCH THE PROGRESSION OF THE
DISTURBANCE TO SEE IF ANY CHANGES BEGIN TO RESEMBLE GFS PREDICTIONS.
MARINE
LITTLE CHANGE IS SEA CONDITIONS IS EXPECTED THE NEXT SEVERAL DAYS.
HAVE TAKEN THE LARGE WAVE MODEL SEA HEIGHTS FROM LATER IN THE WEEK
AND REDUCED THEM TO BETWEEN 5 AND 7 FEET SINCE THE WAVE MODEL IS
BASING ITS WINDS OFF THE GFS GUIDANCE AND ITS DEVELOPING DISTURBANCE.
TROPICAL SYSTEMS
THE LATEST DISTURBANCE TO SHOW UP IN THE SCATTEROMETER ANALYSIS IS A
WEAK CIRCULATION CENTERED SW OF POHNPEI NEAR 4.5N156E. FOR THE PAST
WEEK OR TWO, GFS HAS TAKEN A DISTURBANCE IN THIS REGION AND ZIPPED IT
UP TOWARD THE MARIANAS WHILE THE ECMWF HAS BEEN MORE LAID BACK IN
KEEPING DISTURBANCES SHORT-LIVED AND UNDEVELOPED WHILE STAYING SOUTH
OF 10N. THE ECMWF SHOWS INCREASING MOISTURE OVER THE MARIANAS LATE
WEEK AS A TROUGH, THE REMNANTS OF THE DISTURBANCE, MOVES BY JUST
SOUTH OF GUAM AROUND FRIDAY. WILL HAVE TO KEEP AN EYE ON THE
CIRCULATION IN CASE IT DOES LINGER AROUND LONGER, MORE SIMILAR TO GFS
GUIDANCE.
EASTERN MICRONESIA
ASCAT ANALYSIS INDICATES A NEAR-EQUATORIAL TROUGH RUNS EASTWARD FROM
A WEAK CIRCULATION SOUTHEAST OF YAP AT 5N143E ACROSS SOUTHERN CHUUK
STATE TO ANOTHER WEAK CIRCULATION SOUTHWEST OF POHNPEI AT 4.5N156E.
AREAS OF SHOWERS ARE DEVELOPING OVER CHUUK AND POHNPEI STATES, AND
PATCHY SHOWERS AND ISOLATED THUNDERSTORMS LINGER OVER KOSRAE STATE.
SURGING TRADE WINDS ARE CAUSING SCATTERED SHOWERS NEAR AND SOUTHEAST
OF MAJURO WHILE VERY DRY WEATHER CONTINUES OVER THE NORTHERN RMI.
MODEL GUIDANCE DIFFERS SIGNIFICANTLY. GFS DEVELOPS THE CIRCULATION
SOUTHWEST OF POHNPEI MOVES IT TOWARD NORTHWEST ACROSS CHUUK STATE,
WHILE ECMWF MAINTAINS MORE OF A STATUS-QUO SITUATION, MAINLY JUST
EDGING THE WEATHER PATTERN TOWARD THE WEST. FORECAST CONFIDENCE IS
LOW AT THIS TIME, ESPECIALLY FOR CHUUK, AND THE SITUATION WILL NEED
TO BE MONITORED CAREFULLY.
TRADE-WIND SWELL AND WIND WAVES WILL GENERATE HAZARDOUS SURF ALONG
EASTERN EXPOSURES AT KOSRAE THROUGH TONIGHT, BUT SURF SHOULD START
TO SUBSIDE AND COULD FALL BELOW HAZARDOUS LEVELS BY WEDNESDAY
EVENING.
WESTERN MICRONESIA
THE NEAR-EQUATORIAL TROUGH EXTENDS EASTWARD ACROSS SOUTHERN PALAU
THROUGH A WEAK CIRCULATION SOUTHEAST OF YAP AT 5N143E THEN ACROSS
SOUTHERN CHUUK STATE. ALSO, A SURFACE TROUGH CURVES NORTHWARD FROM
THE CIRCULATION TO JUST WEST OF THE MARIANA ISLANDS, AND PATCHY
SHOWERS AND ISOLATED THUNDERSTORMS ARE NEAR THIS TROUGH AND AROUND
THE CIRCULATION. AREAS OF SHOWERS HAVE REMAINED EAST OF YAP TODAY,
AND MAINLY DRY WEATHER PREVAILS OVER PALAU. THE SYNOPTIC PATTERN IS
NOT EXPECTED TO CHANGE MUCH, BUT SOME SHOWERS WILL WEST TOWARD YAP
AND KOROR DURING THE NEXT COUPLE DAYS, THEN RELATIVELY DRY WEATHER
IS EXPECTED FOR YAP AND KOROR BY THIS WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MARIANAS WATERS...NONE.
W. AYDLETT/SIMPSON
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