The
South Carolina State Fair was lucky and enjoyed great weather for its entire
run which ended today. Dry weather is
expected to continue over the Midlands most of the coming week and it will be
delightful fall weather. However, the
weather pattern will begin changing this week and the Midlands, as well as much
of the East coast, will be challenged by the changing conditions next weekend.
All
of the computer models, used for medium-range weather forecasts, are converging
on a solution that changes the weather for much of North America. The change is already underway. It is happening in the middle troposphere
(500 mb) over western Canada where a double-barrel low pressure system is
pushing the polar jet stream south from Alaska to California.
The 500 mb chart for 00z, 22 Oct 2012. Winds generally blow parallel to the contours lines. Click on the image for a larger view. Image Credit: WSI. |
This
will bring colder air south into the western U.S. The low pressure system will slowly swing
east and become an elongated trough of low pressure. It will extend through the Plains states on
Saturday intensifying a surface low pressure system and moving it north toward
the Arctic. At the same time a tropical
system will be headed north from the Caribbean Sea into the Bahamas.
The
National Hurricane Center (NHC) is keeping tabs on a system south of Jamaica. As of Sunday evening NHC forecasters say
there is a 70% chance of the system becoming a tropical cyclone over the next
two days.
The satellite picture of the Caribbean Sea Sunday evening at 8 p.m. EDT. The I in the center of the picture represents the area being watched by the National Hurricane Center. Image Credit: CIMSS. |
It
is unclear when the system will develop and how long it will remain
tropical. However, all of the models
pick up on this system and move it north.
It would move through the Bahamas next weekend and would be along the
Mid-Atlantic coast by early next week.
What caught my attention was the intensity of the system moving north
and the intrusion of the cold air from the west early next week which could
make this a monster storm.
The
scenario I am describing uses the European computer model (ECMWF) which has
regularly been the superior model at longer ranges. The American (GFS) and Canadian (GEM) are
similar, but do vary in details. At this
time frame the details are usually transitory and may disappear in later model
runs.
According
to the ECMWF there should be some development of the low in the Caribbean
either Tuesday or Wednesday. The weather
map across North America will look something like the map below.
The
tropical system will move north across Cuba late in the week and into the
Bahamas by Saturday. Initially this will
be a slow northward movement. However,
as the system gets farther north the speed will increase. At the same time a cold air mass will begin
invading the central U.S.
Late
the in the week the picture changes dramatically for the eastern third of the
country. The pictures below show the
day-by-day changes beginning on Friday and ending on Monday.
The
tropical cyclone could become a hurricane off the southeastern U.S. before
moving northward and becoming a powerful mid-latitude storm system. This transformation will likely happen late
in the weekend into early next week as cold air rushes into the system from the
west. It will be interesting to watch,
but the effects could be devastating.
The long easterly fetch along the coast could lead to significant storm
surge and beach erosion. Seas could be
dangerous all along the East coast.
In
South Carolina there could be high surf, coastal flooding, and beach erosion
over the weekend. There may even be some
rain for the eastern part of the state, but this will depend on the ultimate
track of the system. A cold front will
pass through the state on Sunday bringing windy conditions both Sunday and
Monday. The coldest air of the fall
season will be pushing into the Southeast behind the front. There could be a frost or freezing
temperatures by the middle of next week once the winds subside.
What
I have presented here is a broad overview of events that will take place over
the next ten days. Obviously, there are
many details yet to be determined and I recognize that this scenario may be
wrong. However, whenever all of the
models are pointing in the same direction, it is best to take heed.
I
will update this information when needed.
Stay tuned!