93WINVEST.15kts-NAmb-126N-1474E.

Moderator: S2k Moderators
Tropical Storm Lan was located southwest of the Marianas. It will
move slowly northwest away from the region, and its direct
impacts will be minimal. However, that doesn`t mean it is going to
be a quiet week. The guidance, to various extents still disagrees
over the next few days before coming into better agreement later
in the week. The models also want to develop a disturbance to the
east of the Marianas, currently near 13N148E before this system
ultimately merges with the tropical storm later in the week. In
the interim, it will likely bring scattered showers and isolated
thunderstorms beginning Tuesday night into Wednesday. There is at
least some model agreement on this, though less so on the timing.
strong easterly flow to the north will bring wind gusts to 30 mph
tonight for Saipan and Tinian before decreasing on Tuesday.
.Marianas Synopsis...
Radar shows what may be a small circulation centered about 50 miles
west of Saipan, but it could also be the eastern end of a sharp
trough extending in from the west. There is no indication of a
closed circulation seen on IR satellite imagery. But a burst of
strong convection over and just west of Tinian and Saipan produced
wind gusts to 51 kt at Saipan airport between 3 and 4 AM and gusts
up to 38 kt on Tinian around the same time. That convection has now
greatly weakened and stratified, and the only strong convection on
satellite is 50-100 miles west of the islands.
&&
.Discussion...
Winds were updated out to about 48 hours to account for more wind
than previously forecast. This brings breezy conditions today to
Tinian and Saipan, which should diminish slightly tonight. The rest
of the forecast is the same as before, with scattered showers
lasting through Thursday night and isolated thunderstorms through
the next week. Forecast confidence is fairly low, as there is
uncertainty surrounding the possible circulation west of Saipan.
Both the GFS and ECMWF show a small but tight circulation developing
this afternoon east of Saipan, then moving away to the east to about
152E, then curving northwest and passing well north of Saipan over
the weekend--a highly unusual pattern.
This morning, JTWC Invest 93W is a major source of uncertainty in
the forecast. The GFS still takes it out to the east to about 152E,
then takes it northwestward, to north of Agrihan, on Sunday. But
the ECMWF now takes it ESE to near 13N152E, then brings it back
WNW through the Marianas between Tinian and Rota on Sunday. This
seems unlikely, but we will keep 93W under close watch. To further
increase uncertainty, satellite seems to show 93W moving southward
along about 147.5E, but it also appears to be weakening with warming
cloud tops. And now, JTWC has just issued a Tropical Cyclone
Formation Alert on this system. Stay tuned for further developments!
Users browsing this forum: No registered users and 3 guests