Scientific Forecaster Discussion
Area forecast discussion...resent
National Weather Service tiyan GU
713 am chst Monday Mar 2 2015
Synopsis...northeast winds and a few showers prevail across
the marianas this morning. Relatively dry weather is expected
through most of the week.
tweaked winds at a few places and added some clouds to forecast
Tuesday and Tuesday night.
Winds have decreased slightly across the marianas compared to Sunday.
2 kft winds on the VAD were 22 knots and the 12z sounding last night
at the same level had winds of 24 knots. Scatterometer pass over
the marianas showed winds of 15 to 20 knots over the marianas.
Winds of 15 to 20 miles per hour today will decrease to 10 to 15 miles per hour tonight.
Winds will increase Tuesday with a further increase Wednesday as
an area of high pressure builds across the northwest Pacific.
Sounding data showed moisture has changed little since yesterday.
00z Sunday sounding data recorded a percipitable water index (pwi)
of 1.26 inches and by 12z it was 1.29 inches. Radar imagery this
morning showed only a few showers moving across the local area.
Isolated showers mentioned in the forecast should suffice.
Models show winds across the area will increase sometime on
Tuesday with breezy conditions possible Wednesday. Low-level
convergence associated with this trade-wind surge will bring in a
few clouds Tuesday and Tuesday night. GFS...ECMWF...navgem and
UKMET all hint at the increase in clouds. Model predictions keep
deep layer moisture lacking though so only expect isolated showers
at best through the forecast.
observations this morning from the ritidian and ipan buoy indicated
seas at around 7 feet. An east and north swell will persist through
much of the forecast. The north swell is expected to remain a
constant two feet through the week. The northeast swell will
increase slightly Tuesday. With the slight increase in winds by
midweek expect combined seas to increase as well.
Fire Weather Watch was extended yesterday to Thursday afternoon.
Not certain if winds will be high enough to generate red flag
conditions today and Tuesday. But with breezy winds possible
Wednesday a red flag warning is likely at that time.
scattered showers and isolated thunderstorms are seen well south
of Pohnpei along the near-equatorial trough while a few
thunderstorms are seen closer to Kosrae and Majuro along a narrow
zone of trade-wind convergence. The near-equatorial trough will
stay well to the south for the week with models showing most
convection remaining just south of Pohnpei and Kosrae. The middle
of the week is expected to be fairly dry at all locations before a
trade-wind surge to the northeast of the Marshalls reaches the
area bringing clouds and showers late in the week. Combined seas
will be between 5 and 8 feet the next several days across the
a large cluster of showers and thunderstorms is seen south and
southwest of Chuuk on the north side of the near- equatorial
trough. Farther west...showers and thunderstorms are developing
just south of Koror. Enhanced infrared satellite imagery shows high
level clouds blowing over Chuuk while the actual storms are
located just south of the coastal waters. However...next shift
will need to monitor for any northward development of showers.
Isolated thunderstorms will remain in the Chuuk area through
tonight before a drier period takes over for midweek. For Yap and
Palau...backed off on onset of scattered showers at Yap until
tonight as convection gradually fills in at both Yap and Koror. By
midweek...showers will push back to the south allowing for a brief
drier period. By late week...a weak trade-wind disturbance will
bring and increase in clouds and showers to all 3 locations.
GU...Fire Weather Watch through Thursday afternoon for guz001.