Karen, TD 13, Florida disturbance 98L, and African disturbance
Tropical Storm Karen is being ripped apart by 20-40 knots of wind shear, thanks to strong southwesterly winds aloft (Figure 1). Satellite loops show that these strong winds have exposed the center of circulation, now visible as a swirl of low clouds, and pushed the remaining heavy thunderstorm activity to the storm's northeast side.
Karen was probably a hurricane yesterday morning, since a NOAA hurricane hunter aircraft that arrived at the storm during the afternoon found winds near hurricane force. These winds were much stronger than the storm's satellite presentation suggested. This flight occurred after Karen had already peaked in intensity, so it is likely Karen was a hurricane for a few hours. The storm may be upgraded to a hurricane in post-storm analysis. It looks right now that Karen does not have much chance to regain hurricane status over the next five days, and may not survive at all. Wind shear over the next five days is predicted to range between 20-30 knots, and there is at least a 30% chance Karen will be destroyed by this. None of the computer models forecast total destruction, though.
Figure 1. This morning's visible satellite image, with yellow contour lines showing the amount of wind shear (in knots) superimposed. Strong upper winds winds blowing from the southwest (shown by the large white arrow) were creating 20-40 knots of wind shear over Karen. These strong winds pushed Karen's heavy thunderstorm activity to the downwind (northeast) side of Karen, exposing the low-level center of circulation to view. Image credit: University of Wisconsin CIMSS.
A severely weakened Karen will not turn to the north as much as the models have been predicting, since the storm will not extend as high in the atmosphere. Shallow storms respond to the wind field closer to the surface. These surface winds are blowing more east-to-west, and Karen is expected to follow a more westerly track to a point a few hundred miles north of the Lesser Antilles Islands five days from now. Steering currents will weaken then, and Karen will move slowly for a few days. It appears likely now that a ridge of high pressure will then build in and force Karen (or its remnants) to the west towards the U.S. East Coast late next week.
Tropical Depression 13
Tropical Depression 13 remains virtually unchanged from a day ago. Satellite imagery shows a small, compact storm that is affecting a very limited portion of the Mexican coast. Wind shear is a low 5 knots, and TD 13 could still strengthen to a 50-55 mph tropical storm before its expected landfall in Mexico on Saturday, between Poza Rica and Tampico. TD 13 will not affect Texas, due to the storm's small size. The next Hurricane Hunter mission is scheduled to arrive at 2 pm EDT today.
Tropical disturbance 98L near the east coast of Florida
A surface low pressure area (98L) moved over South Florida last night, and now appears to be reforming about 100 miles southeast of Cape Canaveral. The system is bringing heavy rain to the waters offshore Florida and the northern Bahama Islands, as seen on long range radar out of Miami. However, there are no organized spiral bands, and winds measured throughout Florida this morning have been 8 mph or less. The system is under about 10-15 knots of wind shear, which may allow some development today. This disturbance has brought rains of up to four inches to portions of South Florida and the western Bahamas, as seen on Miami radar. The center is forming far enough off the coast that 98L will probably not be a big rainmaker for Florida.
The disturbance is lifting northeastward in response to a strong trough of low pressure swinging off the U.S. East Coast. The system has the potential to organize into a tropical depression today or tomorrow, and 98L will pass several hundred miles east of Cape Hatteras, North Carolina Saturday. The system is expected to accelerate to the northeast and could bring heavy rain and high wind gusts to the Canadian Maritime provinces early next week. It is unlikely 98L will have time to become any stronger than a 45 mph tropical storm, and any effects on the U.S. will be minimal.
Coast of Africa wave
A tropical wave about 150 miles south of the Cape Verdes Islands is under about 10-20 knots of wind shear, and has some potential for development over the next few days. This morning's QuikSCAT pass showed an elongated circulation, with top winds of 35 mph to the storm's northeast side.
Wind shear tutorial
For those interested, I've posted a wind shear tutorial. This page is permanently linked on our tropical page.
I'll have an update Friday morning at the latest.
Jeff Masters
Reader Comments
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somebody have a link to the UKMET that goes out past 48hrs?
The UKMET is only run fully on the 0z and 12z runs. Its not really run on the 6Z or 18Z runs.
but once again I state for you that this late La Nina pattern has pushed these conditions back a month, it is still baking here in Florida, all the fronts have fizzled before they get here
this is more like a late August pattern than a late September pattern and that includes the steering, how do you think we got TD 14 out by the CV Islands on Sept 28th? That wouldnt have happened in a "normal" year
and i must give you credit for calling it a couple of weeks agao and saying things might get rolling later in the yr
I don't have the patience for this blog anymore LOL."
Don't make threats! LOL
That is the mid-level circulation and your correct NASH, the LLC is bare and moving WNW.
WELL THATS STUPID! LOL
Chucktown I would love for you to share your knowledge on the occasional CV October East Coast storm
The two that quickly come to mind is Hurricane Hazel in 1954 and Hurricane Gloria in 1985. These were both Cape Verde storms. But again the pattern late next week is not favorable for an east coast strike, unless Karen can "beat" the weakness by speeding up dramatically and at the same time get her act together. Too many ifs, but we'll just have to wait and see.
The GFS 200mb flow does not look particularly favorable at any time in the next week, with even stronger shear expected over the next 36 hours.
I'll certainly continue to watch this system with the path that I expect it to take in case the model is wrong and it can reorganize, but as of right now, I'd say the chances of Karen threatening the US as a major hurricane are remote.
but if you look at the GFS 200mb flow through the next 10 days, I'm pretty confi
Chucktown...that's a pretty bold forecast...Ya gonna say that on the air?
If I had more than 3 minutes I would...LOL
You posted earlier (spagetti models) that you were inclined to go with the BAMS model - unless Karen got stronger.
My question is - What is your prediction on track with "stronger"?
A very weird late season. I'm also in Florida (Pensacola), and it's still summer here. We've still got a month to go -- at the least -- before the Gulf starts cooling down appreciably. Maybe longer.
Go, shear, go!
I posted this yesterday if the sheer is ripping mositure away from the storm isn't it possible that "new moisture" could replace it and cause a huge jump in the westward direction of karen?
okay so the storm jumped south, but it jumped none the less.
paperfrog, I think your right it is difficult to converse on this blog. also, I think the shear is whats going to make karen take a wierd jump later today. there are two smaller "wet" areas that are going to be pulled into her, plus she jumped into warmer water on her west side of the convention. I look for karen to pull through.
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