Flash Flood Warning 4, NWS Guam

Area Forecast Discussion
National Weather Service Tiyan GU
720 AM ChST Sun Aug 19 2018

.Marianas Synopsis..
Tropical Storm Cimaron was located about 520 miles east of Guam at
4 AM, moving west to west-northwest around 15 mph. A monsoon tail
can be seen on satellite imagery extending westward from the south
flank of the storm toward the Marianas. Radar shows scattered
showers developing in the Marianas waters. Winds are moderate from
the west, with 6 to 7 ft seas at Tanapag and Ritidian buoys.

&&

.Discussion...
The basic forecast is little changed, with slightly stronger winds
and the addition of locally heavy rain Monday and Monday night. But
the big picture is the same, with gusty winds, and numerous showers,
heavy at times, from this monsoon surge tonight through Monday night.

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.Marine/Surf...
Revamped the marine grids to remove east swell and replace it with
a more significant NNW swell. Primary swell is now southwest to
west through the next week, but diminishing the second half of this
week. Winds will peak Monday night at 25 kt, but could be a little
higher in far northern Saipan waters. The west swell is not high
enough by itself to produce high surf, but as wind waves rise to
6 to 8 feet, high surf should develop by Monday morning on west
facing reefs. Small Craft Advisory conditions should develop tonight.

&&

.Tropical Systems... As the sun rises this morning, visible satellite
imagery reveals that Cimaron is still sheared under 20-25 kt NE winds
aloft, exposing the northern half of the low-level circulation. The
storm may be veering a little left of model predictions, which could
pose a threat to Tinian and Saipan if it continues.

&&

.Eastern Micronesia and Chuuk...
Tropical Storm Cimaron, centered north of Chuuk near 15N152E,
continues WNW or NW toward the northern Mariana Islands. Isolated
showers and thunderstorms are found south of Cimaron across Chuuk
State. Drier weather is found across Pohnpei, Kosrae and Majuro.
Fair weather will build westward from Pohnpei to Chuuk by tonight. A
trade-wind disturbance southeast of Majuro will bring showers and
thunderstorms to Majuro and Kosrae tonight and Monday, and to Pohnpei
Tuesday and Chuuk on Wednesday as it weakens.

&&

.Western Micronesia Yap and Koror...
IR satellite shows isolated showers and thunderstorms firing up this
morning across Yap and Palau. The monsoon flow in the region will
strengthen in response to Tropical Storm Cimaron the next couple
days. Scattered showers are expected early next week at both
locations with relatively drier weather returning briefly Thursday.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
Marianas Waters...None.

&&

Middlebrooke/M. Aydlett