Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 172141
Area Forecast Discussion
National Weather Service Tiyan GU
741 AM ChST Wed Jan 18 2017
Andersen Air Force Base Doppler weather radar shows a band of
scattered showers within the Guam and Rota coastal waters, with
isolated showers elsewhere in the Marianas waters. The VAD wind
profile reveals east-northeast winds of 25 to 35 knots through the
lowest 10 thousand feet of the air. Above this the winds get
weaker and start turning toward the southeast, the south and
finally toward the southwest at around 25 thousand feet.
Shear line remains large and in charge of the local weather
regime. Winds showed that we actually had a frontal passage, which
is amazing this deep in the tropics. The amount of cold air that
actually got down here was very limited and basically not
noticeable. However, the shear line is producing elevated winds
and seas as well as substantial amounts of rain. These will start
to ease certainly by Friday if not a bit sooner. After the shear
line relaxes its grip on the Marianas, we will return to a dry
season trade-wind regime.
Combined seas of 11 to 13 feet and northeast winds of 20 to 30
knots will make for hazardous conditions for small craft today,
and they could easily last through Thursday night. If you don`t
have to travel, stay on land a couple of days. Also, for those of
us who are landlubbers, the waves will create hazardous surf on
north, east and west facing reefs. Don`t venture near the reef
lines until the surf subsides, especially near Ritidian, Tarague
and Pagat beaches on Guam, which can be particularly dangerous.
Satellite shows two areas of showers, between Pohnpei and Kosrae,
and just east of Kosrae. ASCAT Analysis indicates converging winds
and a couple surface troughs in these areas that are propagating
westward. A few thunderstorms are expected for Kosrae and Pohnpei
today and possibly tonight. GFS Model indicates a convergent low-
level flow and patchy showers will continue at Kosrae and Pohnpei
most of this week. Drier weather is slowly moving across the Majuro
area today, but then models indicate another trade-wind trough and
some showers will move across the marshall islands Thursday through
Friday. Models show the far northern Marshall Islands will remain
very dry, especially above 10N.
Large north swell at Pohnpei and Kosrae will gradually veer to the
northeast. North facing surf will remain hazardous through thursday
and become hazardous along Kosrae`s east facing reefs this evening
and it may persist at Kosrae through the weekend.
Yap and Koror; Satellite and ASCAT Analysis show that a shear line
about 80 miles northwest of yap is edging slightly southward and a
slow-moving surface trough runs southeast of Koror. The shear line
and the trough are pinching together slowly and the flow of moisture
is increasing for both these locations. Models initialize decently
and indicate scattered showers for Yap and Koror on Thursday through
Friday or Saturday. Improving weather is expected over far Western
Micronesia during the weekend.
Relatively dry trade winds remain over Chuuk, and models indicate
only spotty showers the next few days. A trade-wind trough could
arrive from the east this weekend with a few more showers.
High Surf Advisories remain in effect for Koror, Yap and Chuuk.
Large north swell will cause hazardous surf the next day or two
before starting to subside on Friday or Saturday.
GU...High Surf Advisory until 6 AM CHST Friday for GUZ001>004.
Marianas Waters...Small Craft Advisory until 6 AM CHST Friday for