902 
FXPQ60 PGUM 210938
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
400 PM CHST SAT NOV 21 2009

.SYNOPSIS...
AM SOUNDING SHOWED MARKED LOW-LEVEL DRYING...WITH A PWAT OF 1.21 
INCHES. JTWC INVEST AREA 94W IS CENTERED SOUTHWEST OF CHUUK NEAR 
4N147E AND CONTINUES TO SPIN UP. ANIMATED VISIBLE SATELLITE IMAGERY 
SHOWS WELL DEFINED LOW-LEVEL CLOUD LINES FEEDING INTO 94W. WATER 
VAPOR SATELLITE IMAGERY AND GFS INITIAL 200 MB WIND AND DIVERGENCE 
FIELDS SHOW STRONG UPPER-LEVEL DIVERGENCE OVER 94W. NORTHERNMOST 
SPIRAL BAND FROM 94W COMES TO WITHIN 250 MILES OF GUAM.

&&

.DISCUSSION...
NO CHANGES TO FORECAST REASONING. 94W INVEST DOES APPEAR TO BE THE 
ELEPHANT IN THE ROOM AND MODELS REMAIN IN GENERAL AGREEMENT IN 
DEVELOPING 94W INTO A TC...THEN STEER IT IN THE GENERAL DIRECTION OF 
THE FORECAST ZONES. INHERITED FORECAST BRINGS 94W THROUGH DURING THE 
WED NITE/THU AM TIME FRAME. TIMING OF SCATTERED POPS FOR WED AND 
THU STILL LOOKS GOOD. WILL MAINTAIN THEME OF BROAD BRUSHING THE WIND 
FIELDS UNTIL THE DEVELOPMENT AND MOVEMENT OF 94W BECOMES CLEARER. 
LATE IN THE FORECAST PERIOD RIDGING BUILDS BACK IN FROM THE 
SOUTHEAST. BOTH THE GFS AND ECMWF HINT AT ADDITIONAL TC DEVELOPMENT 
IN THE MONSOON TROUGH TO THE SOUTHEAST OF THE FORECAST ZONES...BUT 
WAY TOO EARLY TO NAIL ANYTHING DOWN ON SUCH A FORECAST SCENARIO. AN 
SPSPQ WILL ALMOST CERTAINLY BE NEEDED FOR 94W DURING THE NEXT DAY OR 
SO.

&&

.MARINE/SURF...
12.5 KM QUIKSCAT SHOWS SUSTAINED WINDS OVER THE MARINE ZONES RIGHT 
AT THE 22 KT THRESHOLD. OBS FROM HANDARS AND METARS HAVE NOT BEEN AS 
IMPRESSIVE...BUT CONFIDENCE STILL REMAINS HIGH THAT WINDS WILL 
FRESHEN IN RESPONSE TO HIGH PRESSURE BUILDING TO THE NORTH OF THE 
MARIANAS.

A SMALL CRAFT ADVISORY FOR BOTH WINDS AND SEAS STILL LOOKS LIKELY 
FOR SUNDAY AND SUNDAY NIGHT AS WINDS INCREASE TO 20-25 KT AND SEAS
REACH OR EXCEED 10 FEET. HOWEVER...TRADE SURGE LOOKS JUST WEAK 
ENOUGH TO ALLOW SURF TO PEAK JUST BELOW ADVISORY LEVELS ON NORTH AND 
EAST FACING REEFS DURING THE SAME TIME FRAME. NEVERTHELESS...WILL 
NEED TO WATCH IPAN BUOY CLOSELY TONIGHT AND SUNDAY.

&&

.EASTERN MICRONESIA...
A MONSOON TROUGH IS PERSISTING ACROSS THE ENTIRE REGION WITH TWO 
SMALL CIRCULATIONS EMBEDDED NEAR KWAJALEIN AND NORTHEAST OF MAJURO. 
CONVERGENCE ALONG THE TROUGH AXIS IS EXPECTED TO KEEP UNSTABLE 
CONDITIONS OVER POHNPEI THRU MONDAY NIGHT. SINCE KOSRAE IS FARTHER 
SOUTH OF THE TROUGH AXIS...WEAKER CONVERGENCE SHOULD LEAD TO LESS 
SHOWER COVERAGE THRU SUNDAY NIGHT. LOCATED BETWEEN THE TWO 
CIRCULATIONS...MAJURO IS WITHIN THE DISSOLVED TAIL OF THE MONSOON 
TROUGH. AS A RESULT...ISOLATED SHOWERS WILL PREVAIL THRU THE REST OF 
THE WEEKEND WITH HIGH-LEVEL CLOUDS STREAMING ACROSS FROM CONVECTION 
NEAR KWAJALEIN.
 
FOR EARLY NEXT WEEK...TROPICAL DISTURBANCE 94W NEAR CHUUK WILL PLAY 
A MAJOR ROLE ON THE WEATHER OVER EASTERN MICRONESIA. IF IT DEVELOPS
INTO A TROPICAL CYCLONE AS MOST MODELS HAVE SUGGESTED...IT WILL 
DISRUPT THE MONSOON TROUGH AND CREATE A SOUTHEASTERLY INFLOW TOWARD 
THE CYCLONE ITSELF. IT CAN SEND A MODERATE SOUTHWEST SWELL INTO 
POHNPEI. HOWEVER THIS CAN ACTUALLY BRING A PERIOD OF RELATIVELY FAIR 
CONDITIONS FOR THE AREA BEFORE TRADE-WIND CONVERGENCE SETS IN AROUND 
MIDWEEK.

&&

.WESTERN MICRONESIA...
TROPICAL DISTURBANCE 94W JUST SOUTHWEST OF CHUUK WILL LIKELY KEEP 
INCLEMENT WEATHER OVER CHUUK STATE THRU SUNDAY NIGHT. AS IT MOVES 
NORTHWESTWARD AND STRENGTHENS EARLY NEXT WEEK....CONVERGING 
SOUTHEAST WINDS TO THE EAST OF 94W ARE ANTICIPATED TO PROLONG 
WETNESS OVER THE AREA. DEPENDING ON THE STATUS OF 94W...A SOUTHWEST 
SWELL MIGHT CREATE HIGH SURF SCENARIO ALONG SOUTH AND WEST SHORES AS 
WELL. BY MIDWEEK...94W WILL BE FARTHER NORTHWEST OF THE STATE SO 
THAT DECREASING CONVERGENCE SHOULD BRING GRADUAL IMPROVEMENT.

FREQUENT SHOWERS AND POSSIBLE THUNDERSTORMS WILL ACCOMPANY PALAU 
INTO EARLY NEXT WEEK AS THE MONSOON TROUGH REMAINS IN THE VICINITY. 
DRIER NORTHEAST TRADE WINDS NORTH OF THE MONSOON TROUGH ARE GOING TO 
PREVENT THESE SHOWERS FROM SPREADING OVER YAP FOR ANOTHER 24 TO 36 
HOURS. AFTERWARD...AFOREMENTIONED 94W WILL BEGIN TO LIFT THE MONSOON 
TROUGH NORTHWARD TOWARD YAP WITH INCREASING SHOWER COVERAGE. STRONG 
MID TO UPPER-LEVEL SUBSIDENCE RELATED TO A RIDGE OF HIGH PRESSURE 
JUST NORTHEAST OF THE MARIANAS SHOULD STEER 94W NORTHWESTWARD 
PASSING BETWEEN YAP AND GUAM AROUND MIDWEEK. SINCE IT IS STILL TOO 
EARLY TO DETERMINE THE FUTURE TRACK OF 94W AT THIS POINT...HAVE ONLY 
INTRODUCED CLOUDINESS AND HIGHER WINDS IN THE FORECAST. RESIDENTS IN 
BOTH YAP STATE AND THE REPUBLIC OF PALAU NEED TO MONITOR 94W CLOSELY 
FOR THE NEXT SEVERAL DAYS. AFTER MIDWEEK...BOTH 94W AND THE MONSOON 
TROUGH AXIS WILL BE NORTH OF BOTH LOCATIONS BUT WEST WINDS ARE 
EXPECTED TO MAINTAIN SOME SHOWERS AROUND. NOW THRU SUNDAY EVENING... 
THE COMBINATION OF TRADE-WIND SWELLS AND WIND WAVES WILL KEEP SEA 
HEIGHTS AROUND 7 TO 8 FEET. ON MONDAY...94W CAN BEGIN TO INCREASE 
NORTHEAST SWELLS AND DEVELOP A HIGH SURF EVENT ALONG NORTH SHORES OF 
PALAU AND YAP.

&&

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

$$

MCELROY/CHAN