Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Fri, 17 Sep 2010 03:10:57 -0500

883 
FXPQ60 PGUM 170810
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
610 PM CHST FRI SEP 17 2010

.SYNOPSIS...LATEST SATELLITE IMAGERY AND RADAR SHOW ISLAND
THUNDERSTORMS OVER THE GUAM REGION WHILE THE REST OF THE MARIANAS
HAVE DRIED UP AHEAD OF THE NEXT BATCH OF WEATHER WELL TO THE
EAST. WATER VAPOR IMAGERY SHOWS THAT WE ARE NOW BEGINNING TO
RECEIVE OUR MOISTURE IN ADVANCE FROM THE APPROACHING TROUGH WITH
THE HIGHER CLOUDS REACHING US BY TONIGHT...AND SUGGEST SOME VERY
ISOLATED THUNDERSTORMS IN THE MARIANAS WATERS ARE POSSIBLE OVER
THE NEXT 24 HOURS. WE STILL EXPECT THE PRIMARY THRUST OF WEATHER
TO NOT REACH US UNTIL LATE SATURDAY OR SUNDAY...LASTING INTO
MONDAY.

&&

.DISCUSSION...KEPT THE FORECAST SCENARIO FROM THE LAST TWO RUNS
ALTHOUGH THE TROUGH AXIS SEEMS TO HAVE REPOSITIONED ITSELF
FURTHER TO THE EAST...AND THE LATEST FORECAST RUNS GIVE A SLIGHT
HINT THAT THIS AREA MAY BREAK INTO TWO PARTS WITH THE NORTHERN
HALF FORMING A TROPICAL CYCLONE NORTH OF 20N AND THE
MARIANAS...TOWARDS IWO JIMA. THE SOUTHERN PART...MEANWHILE...IS
EXPECTED TO CONTINUE OVER THE MARIANAS ON SUNDAY AND MONDAY WITH
PERHAPS A LITTLE LESS STRENGTH. IN ANY CASE IT DOES NOT TAKE TOO
MUCH OF AN IMPULSE TO CREATE SCATTERED SHOWERS DURING THIS TIME
OF THE YEAR. ALTHOUGH QUITE A WAYS OFF...BOTH THE ECMWF AND GFS
SUGGEST A MOIST TAIL MAY RESULT FROM THE CYCLONE DEVELOPMENT TO
THE NORTH AND EITHER KEEP US OR BRING US BACK INTO SCATTERED
SHOWERS LATER IN THE WEEK. JUST SOMETHING TO THINK ABOUT AS THE
CIRCULATION HAS YET TO EVEN BREAK OUT OF THE TROUGH NOW LOCATED
NEAR 159E.

IN THE VICINITY OF OKINAWA...TYPHOON FANAPI CONTINUES TO
INTENSIFY BUT I BELIEVE THAT ANY WESTERLY FETCH WILL BE TOO SMALL
AND TOO FAR AWAY TO HAVE ANY SIGNIFICANT EFFECT ON THE MARIANAS.

&&

.EASTERN MICRONESIA...
DRIER TRADES ALREADY OVER MAJURO ARE EXPECTED TO PROMOTE FAIRER
CONDITIONS WESTWARD OVER THE WEEKEND AT EASTERN MICRONESIA
...HOWEVER LATEST ASCAT SATELLITE IMAGERY CONTINUES TO SHOW A
MODERATE TO FRESH TRADE-WIND SURGE APPROACHING THE DATE LINE
BETWEEN 5N AND 15N. AN ITCZ FORMED ALONG THE SOUTHERN EDGE OF THE
SURGE...ORIENTING NORTHEASTWARD FROM 5N175E TO WELL SOUTH OF THE
HAWAIIAN ISLANDS. CONVECTION ASSOCIATED WITH THE LEADING EDGE OF
THE ITCZ IS FLARING UP AROUND 5N175E EASTWARD TO BEYOND THE
DATELINE. ANTICIPATE THIS CONVECTION TO SPREAD OVER MAJURO BY
SATURDAY EVENING AND GRADUALLY EXTEND WESTWARD DURING EARLY NEXT
WEEK. BECAUSE OF THIS CONVERGENCE AND MODEL AGREEMENT... HAVE
INTRODUCED SCATTERED SHOWERS TO THE KOSRAE FORECAST ON
SUNDAY...AND TO THE POHNPEI FORECAST ON SUNDAY NIGHT.

&&

.WESTERN MICRONESIA...
FOR KOROR AND YAP...A SURFACE RIDGE IS ANCHORED OVER WESTERN
MICRONESIA WITH LIGHT AND VARIABLE WINDS. BOTH WV SATELLITE
IMAGERY AND THE YAP SOUNDINGS INDICATE A DRYING TREND AT MID TO
UPPER LEVELS ADVECTING NORTHWESTWARD FROM THE EQUATOR. THE
COMBINATION OF THESE TWO INDICATORS SUPPORT QUIET WEATHER FOR
BOTH YAP AND PALAU THRU THE WEEKEND. WITH TYPHOON FANAPI ALREADY
NORTH OF 20N...THE SURFACE RIDGE IS SHIFTING NORTHWEST OF THE
REGION. THIS SHOULD ALLOW GENTLE TO MODERATE TRADE WINDS TO
FILTER BACK OVER WESTERN MICRONESIA. HOWEVER...TRADE-WIND
DISTURBANCES EMBEDDED WITHIN THE TRADE-WIND FLOW MIGHT INTRODUCE
MORE SHOWER ACTIVITY. FOR CHUUK...A WEAK SURFACE TROUGH MIGRATING
SLOWLY WESTWARD ALONG GENTLE TRADE WIND FLOW WILL KEEP SOME
SHOWERS OVER CHUUK THRU SATURDAY AFTERNOON...THEN THE DRIER
TRADES ENTERING EASTERN MICRONESIA WILL REACH CHUUK EARLY NEXT
WEEK.

&&

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

$$

EDSON/DEVITA

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.