Flash Flood Warning 13, NWS Guam

Area Forecast Discussion
National Weather Service Tiyan GU
518 PM ChST Wed Oct 24 2018

.Marianas Synopsis...
STY Yutu is centered at 13.9N, 147.1E at 430 PM, about 125 miles
SE of Tinian/Saipan, and 160 miles east of Guam, moving WNW at
about 13 mph with max winds of 150 mph. Clouds cover the Marianas
with winds gusting to around 55 mph at Tinian and Saipan and near
45 mph at Guam and Rota. During the afternoon, Yutu wobbled to the
NW for a couple of hours, but has now wobbled back to a WNW track
that is currently aimed just south of Tinian. Seas have risen to
13 feet at Ipan, and are around 8 feet at Tanapag.

&&

.Discussion...
The forecast is virtually unchanged, the only adjustment being to
go with scattered locally heavy showers rather than numerous at
Guam tonight. The way Yutu's track has been wobbling back and forth
this afternoon, it's difficult to pinpoint which island will get hit
hardest, but at present Tinian and Saipan appear to be the prime
targets. A direct hit on either island would be catastrophic, with
sustained winds over 150 mph likely as the eye passes around midnight
or shortly thereafter. Residents of those islands should make sure
they get to a secure shelter before dark.

&&

.Marine...
As noted above about Guam's weather tonight, the only change to the
forecast was scattered instead of numerous showers tonight for Guam
waters.

&&

.Tropical systems...
Satellite imagery and detected lightning both indicate that STY Yutu
is still intensifying, and will likely pass Tinian/Saipan with max
winds of 160 mph around 1 AM tonight. Yutu's track has been wobbly,
as noted above, so residents of Tinian, Saipan, and even Rota, should
prepare for the worst tonight from a very dangerous Category 5 super
typhoon.

&&

.Eastern Micronesia...
ASCAT Analysis indicates a surface trough persists from near Kosrae
northeastward through a weak circulation southwest of Majuro to
beyond 12N180. Patchy showers and isolated thunderstorms are over
Kosrae State and the Marshall Islands within about 200 miles of the
surface trough. Fair weather and light winds prevailed for Pohnpei
today. The surface trough and weak circulation should drift toward
the west-northwest during the next few days and cause patchy showers
over eastern Micronesia through the end of this week. Models also
indicate another trough with areas of showers could arrive from the
east next week.

&&

.Western Micronesia...
High Surf and Small Craft Advisories remain in effect a Chuuk. Moist
southwest monsoon flow will continue across Chuuk the next couple of
days. Conditions should start improving by Saturday as Super Typhoon
Yutu moves farther west of the Marianas and good weather is expected
at Chuuk on Sunday and Monday.

For Yap and Koror, satellite shows a band of showers and
thunderstorms between Yap and Koror and patchy showers are over most
of western Micronesia. Westerly monsoonal flow will increase over
far western Micronesia the next few days. Also, as STY Yutu moves
farther west of the Marianas over the Philippine Sea, a north swell
will start arriving at Yap and Koror on Thursday, and hazardous sea
and surf conditions could develop on Friday and continue through the
weekend into next week.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Flash Flood Watch through late Thursday night for GUZ001>004.

     Tropical Storm Warning for GUZ001.

     Typhoon Warning for GUZ002>004.

Marianas Waters...Tropical Storm Warning for PMZ151.

     Typhoon Warning for PMZ152>154.

&&

Middlebrooke/Simpson/Ziobro