Flash Flood Warning 9, NWS Guam

Area Forecast Discussion
National Weather Service Tiyan GU
507 PM ChST Mon Sep 10 2018

.Marianas Synopsis...
Typhoon Mangkhut is moving through the Marianas with the eye about
to cross right over Rota at 445 PM. Winds have gusted to 58 mph at
the Guam airport, 82 mph on Saipan, and 75 mph on Rota.

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.Discussion...
Everything has happened as expected so far, with Mangkhut crossing
over Rota and tropical storm to typhoon conditions occurring in
the Marianas. Forecast has basically been unchanged, with only a
few adjustments to winds. Tuesday will see much i9mproved conditions,
but moist unstable air will linger through the week with isolated
thunderstorms through Friday.

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.Marine...
Seas have risen to 20+ feet, with max waves hitting 30 ft at the
Tanapag buoy. Surf will remain dangerous for a couple more days
after the typhoon.

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.Tropical systems...
Mangkhut had been slow to intensify earlier, with the eye forming
and re-forming on radar several times during the day. But in the
last hour it appears to be getting better-formed on radar, with
hundreds of lightning strikes indicated in the southern and eastern
eyewall in 5 minutes. The eye has passed closest approach to Tinian
and Saipan, is now hitting Rota directly, and will pass about
45 miles NNW of Guam around 8 PM.

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.Eastern Micronesia and Chuuk...
A surface trough runs southeastward from Typhoon Mangkhut located
near Rota thru a circulation (91W) near Majuro at 6.5N169E to beyond
the Date Line at 8N. A surface ridge and partly cloudy skies persist
over Pohnpei and Chuuk today. The circulation has become much better
organized today than yesterday even though models indicate it should
gradually weaken. For this forecast, the circulation is expected to
continue moving west-northwest this week. Showers will linger over
Majuro tonight thru Tuesday, move over Kosrae State tonight and
Tuesday, to Pohnpei Tuesday and Wednesday, and possibly to Chuuk
by Thursday and Friday.

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.Western Micronesia...
The Yap and Koror forecasts are now headlined for hazardous sea
conditions by Tuesday night. A monsoon trough extends northeastward
from a circulation north of Koror at 12N134E into Typhoon Mangkhut
currently near Rota. Models still indicate that as Mangkhut moves
west of the Marianas Tuesday across the Philippine Sea this week,
then the monsoon flow will increase dramatically over far Western
Micronesia. Shower coverage, winds and waves will increase for both
Yap and Koror on Tuesday and continue through Thursday. Improving
weather is expected for Yap and Koror by Friday or Saturday.

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.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Typhoon Warning for GUZ001>004.

Marianas Waters...Typhoon Warning for PMZ151>154.

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Middlebrooke/Simpson/Kleeschulte