Flash Flood Warning 4, NWS Guam

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
600 PM CHST SAT JUL 4 2015

.SYNOPSIS...
TS CHAN-HOM IS CENTERED ABOUT 190 MILES EAST OF GUAM NEAR 13.2N
AND 147.6E. WHILE CHAN-HOM APPEARED TO BE GETTING ORGANIZED AT
LAST THIS MORNING...ITS SATELLITE SIGNATURE HAS ONCE AGAIN
DETERIORATED THIS AFTERNOON AS IT RUNS AFOUL OF AN UPPER-LEVEL LOW
OVER THE MARIANAS. BUT SATELLITE AND RADAR SHOW PLENTY OF CLOUDS
AND SHOWERS MOVING INTO THE MARIANAS.

&&

.DISCUSSION...
WITH THE FORECAST BASED ON THE 1 PM WARNING FROM JTWC...HAVE
ISSUED A TY WARNING FOR TINIAN AND SAIPAN...AND A TS WARNING FOR
ROTA. CHAN-HOM SHOULD PASS SAIPAN AROUND 4 PM SUNDAY AFTERNOON.
OF COURSE...TYPHOON CONDITIONS FOR TINIAN-SAIPAN ARE PREDICATED ON
CHAN-HOM ACTUALLY ACHIEVING TYPHOON STATUS...AND AS IT CURRENTLY
LOOKS ON SATELLITE THAT DOES NOT SEEM VERY LIKELY. MUCH DEPENDS ON
HOW CHAN-HOM COPES WITH THE EFFECTS OF THE UPPER LOW OVERNIGHT. IN
ANY CASE...IT APPEARS ALL THE ISLANDS WILL GET PLENTY OF RAIN
TONIGHT THROUGH SUNDAY NIGHT...PROMPTING THE FLASH FLOOD WATCH NOW
IN EFFECT.

&&

.EASTERN MICRONESIA...
TROPICAL STORM NANGKA CONTINUES TO MOVE AWAY FROM MAJURO TOWARDS
ENEWETAK ATOLL. THE TROPICAL STORM WARNING IS NO LONGER IN EFFECT
FOR WOTJE AND UTIRIK ATOLLS BUT A TYPHOON WATCH FOR ENEWETAK ATOLL
AND A TROPICAL STORM WATCH CONTINUES FOR KWAJALEIN AND UJAE ATOLLS.
EXPECT STEADILY IMPROVING CONDITIONS OVER THE NEXT COUPLE OF DAYS AT
MAJURO AS NANGKA MOVES AWAY. A DRIER PATTERN IS EXPECTED AT MAJURO
NEXT WEEK WITH A TRADE-WIND PATTERN TRYING TO ESTABLISH ITSELF
ACROSS THE REGION BY THE MIDDLE OF NEXT WEEK. MONSOON-RELATED
SHOWERS AND THUNDERSTORMS ARE PROGGED TO STAY PRIMARILY NORTH OF
KOSRAE FOR THE NEXT SEVERAL DAYS. UNSETTLED WEATHER MAY AFFECT
POHNPEI SUNDAY NIGHT INTO MONDAY NIGHT AS NANGKA MOVES NORTH OF
POHNPEI AND CAUSES A ZONE OF LOW-LEVEL CONVERGENCE TO DEVELOP SOUTH
OF THE TROPICAL STORM OVER POHNPEI. DRIER CONDITIONS WILL RESUME
TUESDAY THROUGH THURSDAY AT POHNPEI AS THE INFLUENCE OF NANGKA WANES
AS IT MOVES NORTH OF CHUUK STATE.

SEA CONDITIONS REMAINS HAZARDOUS FOR POHNPEI AND MAJURO WHILE SEAS
HAVE FALLEN AT KOSRAE ENOUGH TO DROP THE HEADLINE IN THE KOSRAE
FORECAST. SURF WILL GRADUALLY FALL OVER THE NEXT 24 HOURS AND SHOULD
FALL BELOW HAZARDOUS LEVELS AT ALL LOCATIONS BY SUNDAY NIGHT AS
MONSOON GENERATED SWELL AND WIND WAVES DIMINISH.

&&

.WESTERN MICRONESIA...
THE 00Z CHUUK SOUNDING SHOWS IMPRESSIVE 50 KT SOUTHWEST MONSOON FLOW
WITHIN A LAYER FROM 2800 TO 6000 FT AGL. SATELLITE IMAGERY AND ASCAT
DATA SHOW THIS EVENT CONTINUING THROUGH THE AFTERNOON HOURS.
MODELS DO DECREASE WINDS OVER CHUUK TONIGHT AND TOMORROW BUT CHUUK
OBSERVATIONS INDICATE A RELATIVELY HIGH VERTICAL SHEARED ENVIRONMENT
OVER CHUUK WATERS. THUS...HAVE ADDED A WIND SHEAR GROUP AND
INDICATED HIGHER GUSTS IN SHOWERS IN THE FORECAST FOR TONIGHT.
WEATHER WILL IMPROVE SUNDAY AND SUNDAY NIGHT BUT SCATTERED SHOWERS
ARE EXPECTED TO RETURN MONDAY AND TUESDAY AS EFFECTS FROM NANGKA
BECOME REALIZED.

RIDGING WILL KEEP MAINLY DRY WEATHER OVER KOROR THROUGH THE NEXT
SEVERAL DAYS. YAP WEATHER WILL REMAIN UNDER RATHER UNSETTLED WEATHER
FOR THE NEXT COUPLE OF DAYS. DRIER CONDITIONS WILL RESUME TUESDAY AS
CHAN-HOM MOVES INTO THE PHILIPPINE SEA AND DRAGS ACTIVE
MONSOON WEATHER NORTH OF YAP.

FRESH TO OCCASIONALLY STRONG MONSOON FLOW WILL KEEP SWELL AND WIND
WAVES HIGH ENOUGH TO PROLONG HAZARDOUS SURF AT YAP AND KOROR THROUGH
AT LEAST SUNDAY NIGHT. SEAS WILL FALL GRADUALLY OVER THE REST OF THE
WEEKEND ALLOWING THE SMALL CRAFT ADVISORY HEADLINE TO EXPIRE OR BE
CANCELLED BY SUNDAY NIGHT.

THE STRONG MONSOON FLOW WEST OF CHUUK STATE WILL PROMOTE CONTINUED
SWELL GENERATION AND WIND WAVES CAUSING HAZARDOUS SURF TO CONTINUE
ALONG SOUTH AND WEST FACING REEFS THROUGH AT LEAST SUNDAY NIGHT.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...TYPHOON WATCH FOR GUZ001-002.

     FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR GUZ001>004.

     TROPICAL STORM WARNING FOR GUZ002.

     TYPHOON WARNING FOR GUZ003-004.

MARIANAS WATERS...TYPHOON WATCH FOR PMZ151-152.

     TROPICAL STORM WARNING FOR PMZ152.

     TYPHOON WARNING FOR PMZ153-154.

&&

MIDDLEBROOKE/WILLIAMS