September 28, 2014
A weak front sagging south will lead to a few showers from the
northern Plains into the Great Lakes on Monday. This weakening front
can lead to spotty light showers across MI, northern IN, and OH into
the Northeast on Monday night and Tuesday. Rainfall with this front
will be light. Still dry and warm elsewhere across the Plains and
Midwest through Tuesday, but slight cooling is likely in the upper
Midwest and Great Lakes on Monday and Tuesday. A strong low and its
associated front will push into the Plains Monday night and Tuesday.
The low will lift into Canada while the trailing front spreads rain
and thunderstorms southeastward across the Plains and Midwest from
Tuesday into Friday. Rainfall of 0.50-1.25 inches (13-32mm) still
looks reasonable with this feature. Dry and cooler in the wake of this
front by the weekend with highs mainly in the 50s, 60s, and low 70s
(12-24C) across the Midwest for Saturday and Sunday. Rather chilly
Friday night with lows 34-40 (1-5C) in MN, IA, and WI, but no killing
frost or freeze is expected. The models differ on the timing of
disturbances moving through the mean trough position over the Midwest
next week. These features do not look like big rain makers but can
lead to spotty light showers on occasion. At this point leaned toward
the ECMWF timing since there is some support from several ensembles.
The GFS shows a widespread frost possible across the eastern Dakotas
to WI and northern IA next Wednesday night, but the ECMWF is
significantly milder with no signs of frost. So not sold on the GFS
frost idea around day 10. The models differ on the details in the
11-15 day period, but most look drier than normal across much of the
Plains and Midwest with temperatures near to below normal.
Hurricane Rachel has now begun to weaken a bit, after the storm's peak
strength was reached overnight. It is now producing sustained winds of
75 mph as it churns across the open waters of the eastern Pacific
Ocean, about 485 miles to the west of the southern tip of Baja
California. Rachel will continue to weaken over the next several days.
Rachel's movement to the north-northwest has slowed to 5 mph and the
storm will continue to slow today and likely become nearly stationary
in the next day or so. A combination of entrainment of more dry air
from the north, increasing environmental wind shear and the upwelling
of cooler waters beneath the slowing storm will contribute to Rachel's
weakening, and it will weaken to a tropical storm tonight or early
Monday. Rachel is expected to take a more west or southwest drift
during the beginning of the week, then probably dissipate during the
middle of the week. Outside of some rough surf and rip currents across
the western coast of Baja California, no direct impacts to land are
expected from Rachel.
Elsewhere, a cluster of disorganized convection a few hundred miles
south of Guatemala is expected to gradually get better organized as it
tracks northwestward through the upcoming week. While imminent
development is not expected over the next 24-48 hours, an acquisition
of tropical characteristics is looking likely later in the upcoming
As of Monday morning, EDT, Tropical Storm Kammuri was located
approximately 360 miles east-southeast of Narita Airport, Japan.
Kammuri is moving northeast at 16 mph. Maximum sustained winds are 50
mph with gusts to 65 mph. Kammuri is forecast to continue to weaken as
it moves northeastward away from Japan. Despite missing Japan, this
storm will bring rough surf and rip currents for the next few days to
the eastern facing coastlines of Japan.
Tropical Storm 18W was located approximately 340 miles north of Chuuk.
Movement is to the west at 13 mph. Maximum sustained winds are 40 mph
with gusts to 50 mph. This storm is forecast to move continue to
strengthen over the next few days and move northwestward passing north
of Guam. Eventually, this storm may become a typhoon and move towards
Kadena, Japan by the end of the week.
Widely separated showers and storms will fire Formosa and Chaco to
Misiones and Corrientes on Monday, while the rest of the Argentina
croplands have dry weather. A weak cold front will spreads a few
showers and storms northward across Argentina on Monday night and
Tuesday. Moisture looks limited with the front so rainfall will be
generally light and spotty. Dry across Argentina on Wednesday and
Thursday. A moist and slow-moving frontal system will lift slowly
northward across the Argentina croplands from later Friday through
Sunday. A few showers and storms may linger toward the Paraguay border
next Monday as the front stall over the mid-continent. A wave of low
pressure is shown to move along the front next week which may allow
showers and storms to spread back southward to Entre Rios, Santa Fe,
and northern BA for next Tuesday and Wednesday, while scattered rains
persist farther north. Most of Argentina looks to be drier than normal
in the 11-15 day period, but rainfall can be close to normal toward
the Paraguay border. Across Brazil, A front stalled over southern
Brazil will lead to showers and thunderstorms from RGS to SP and MGDS
through Wednesday. The heaviest rains are expected from northern RGS
to Parana. A weak front will help nudge this front north into
Center-West Brazil around midweek with scattered showers and storms
possible from Minas Gerias to Matto Grosso from Tuesday into next
Sunday. Meanwhile, southern Brazil will have a spell of dry weather
from Thursday into next weekend. The models differ on the timing of a
front coming into southern Brazil next week with the GFS now holding
off the the rain until next Wednesday. The ECMWF and a few ensembles
show this front leading to scattered rains across RGS and SC from
later Monday through Wednesday of next week. Stuck with the ECMWF
timing but kept rain amounts less than what the ECMWF is showing.
Meanwhile, most modeling is now showing dry weather to continue across
Parana, SP, and MGDS from Thursday through next Wednesday.