Scientific Forecaster Discussion
Area forecast discussion
National Weather Service tiyan GU
639 am chst sun Mar 29 2015
a diffuse shear line is keeping skies mostly cloudy over the
marianas...but radar shows only isolated showers...mainly over
Guam and Rota waters. The ipan buoy is reporting seas between
6 and 7 feet. The radar is indicating winds of 20 to 25 knots at
2000 to 3000 feet.
have made little change to the forecast. Winds should be fresh to
strong the next couple of days as Typhoon Maysak passes well south
of the marianas. It appears from model guidance that scattered
showers and isolated thunderstorms will hold off until Monday
night...and adjusted the forecast accordingly.
have left winds fresh to strong through Monday night...after which
winds should diminish to moderate to fresh as Typhoon Maysak moves
away. Seas may get a little higher than currently forecast around
Monday and Tuesday...depending on Maysak.
converging southeast winds feeding toward Typhoon Maysak will
keep scattered showers near Pohnpei today. By this evening...a
surface ridge already over Kosrae will build westward and usher in
drier conditions. A robust trade-wind disturbance will move through
the Marshall Islands through tonight. Expect periodic heavy showers
and isolated thunderstorms to continue near Majuro until Monday.
This same disturbance will also reach Kosrae by Monday
evening...and Pohnpei on Tuesday. By midweek...much drier trade
winds associated with a surge should promote partly cloudy skies
near Majuro and Pohnpei. For Kosrae...a trade convergence zone
near 4n along the southern extent of this surge might be close
enough to maintain some showers through midweek.
A trade-wind surge has developed south of the Hawaiian islands.
These surging trades will gradually make their way westward across
the date line into eastern micronesia in a couple of days. In
response...trade-wind waves and swell are going to build across
Kosrae and the Marshall Islands starting Monday evening. Need to
monitor for possible high surf and hazardous seas for small craft.
Typhoon Maysak is about to hit Chuuk lagoon in the next few hours.
Typhoon force winds are expected through noon today then decreasing to
tropical storm winds in the afternoon as Maysak slowly pulls
away. Heavy rain and scattered thunderstorms this morning should
decrease to numerous heavy showers and isolated thunderstorms by
this afternoon. Hazardous seas and dangerous surf will continue
through the day before gradually subsiding tonight and Monday.
Afterward...sporadic convection will linger around The Lagoon
through Monday in converging southeast winds. By Monday night...the
surface ridge shifting westward from eastern micronesia should
provide improvement. Wet weather might return near midweek as a
trade disturbance from the east arrives.
The combination of a surface trough and a shear line will continue
to trigger isolated thunderstorms near Yap until late this evening.
These features are anticipated to shift west of Yap and over Koror
by early Monday morning. As strengthening Typhoon Maysak departs
Chuuk state and turns west-northwestward into eastern Yap state on
Monday...subsidence west of Maysak could support pleasant weather
near Yap. For Koror...Maysak will lift the near-equatorial trough
currently near 4n northward closer to the capital. This could
generate more isolated thunderstorms there through Tuesday. Maysak
will likely play a major role on the middle-term forecast of both
Koror and Yap. The future tack of Typhoon Maysak will determine
the distribution of winds and rain among both locales.
Latest altimetry and computer model guidance data indicate a
downward trend on the seas and northeast swell near the Republic of
Palau and Yap state. This will allow surf to drop below hazardous
levels later this afternoon. Seas and surf will build again Tuesday
morning as Typhoon Maysak approaches.
Marianas waters...Small Craft Advisory until 6 am chst Tuesday