Danny weakens; not likely to become a hurricane
Tropical Storm Danny has weakened. Data from the Hurricane Hunters between 2 - 3 pm EDT showed top winds of just 40 - 45 mph at the surface. Satellite intensity estimates of Danny's strength have also declined since this morning. Danny's satellite appearance is pretty unconventional, and the storm doesn't look much like a tropical cyclone. The low level circulation center is exposed to view, with the heaviest thunderstorms lying several hundred miles east of the center. The center has remained nearly stationary the past four hours, and has grown less distinct. It is possible that a new center will form up to 100 miles to the east, in the region with the heaviest thunderstorm activity. Danny has already undergone several center relocations over the past 12 hours.
Figure 1. Afternoon satellite image at 3:17 pm EDT of Danny, showing the exposed swirl of clouds where Danny's center is, well displaced from the heaviest thunderstorm activity to the east.
The forecast for Danny
There's not much new to report from the latest set of 12Z model runs for Danny. The models have pretty much maintained their previous forecast, calling for Danny to intensify to a Category 1 hurricane by Saturday morning, and pass close to both Cape Hatteras, NC, and Cape Cod, MA. Given that the models did not correctly forecast Danny's current struggles, I believe it is unlikely that Danny will attain hurricane strength. Dry air from the upper-level low that has been keeping Danny disorganized continues to be a problem for the storm, despite the presence of moderate wind shear of 10 - 15 knots. Danny only has about 24 hours of relatively favorable wind shear left, and that is probably not enough time to intensify into a hurricane. By Friday night, a trough of low pressure will approach the U.S. East Coast and bring high wind shear of 20 - 35 knots. Danny will be close enough to this trough that the trough may be able to feed energy to Danny as the trough converts Danny to an extratropical storm. As a result, Danny may not weaken only slowly. A landfall in Cape Cod, eastern Maine, or Nova Scotia as a tropical storm with 45 - 55 mph winds is a reasonable forecast.
Figure 3. Tropical wave 94L off the coast of Africa.
Invest 94L off the coast of Africa
A well-organized tropical wave (94L) lies a few hundred miles southwest of the Cape Verdes Islands, near the coast of Africa. This disturbance continues to look more organized on satellite imagery. Shear is low, about 10 knots, and waters are warm enough to support continued development. The dry Saharan Air Layer is relatively limited in extent and intensity, so dry air may have only a small inhibiting effect on the wave. Expect continued development of this wave as it moves westward over the next few days. NHC is giving this system a medium (30 - 50% chance) of developing into a tropical depression by Saturday. This system is moving rather slowly, 10 - 15 mph. The GFDL and HWRF models both predict 94L will be a Category 1 hurricane five days from now. These models also predict that 94L will take a significant northward jog 3 - 5 days from now, in response to a strong trough of low pressure passing to the north (this is the same trough of low pressure that will be recurving Danny out to sea).
I'll have an update Friday morning.
Jeff Masters
Reader Comments
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That happened a couple years ago with a TS that hit NC. It sheared apart at landfall so when the center hit it was just sprinkles but a small area to the east got 50-60mph winds and alot of rain. Everyone kept asking me where the ts was.
Model runs start from about 10N and 32W, when it actuality it's near 10N and 38W based on the relocation.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
423 AM AST FRI AUG 28 2009
.DISCUSSION...NO SIGNIFICANT WEATHER FEATURE TO AFFECT THE LOCAL
AREA FOR THE NEXT COUPLE DAYS. NEXT TROPICAL WAVE TO ENTER THE
EASTERN CARIBBEAN ON MONDAY AND THEN AFFECT THE LOCAL ISLANDS LATE
MONDAY INTO TUESDAY. EXPECT A PLEASANT UPCOMING WEEKEND FOR MUCH
OF THE CWA...WITH SLIGHT CHANCES OF RAIN. HOWEVER...SECTIONS OF
WESTERN PUERTO RICO MAY EXPERIENCE A FEW MODERATE TO LOCALIZED
NUMEROUS SHOWERS THIS AFTERNOON.
FEW TROPICAL WAVES CROSSING THE FAR TROPICAL ATLANTIC...LOOKING
INTERESTING AT THIS TIME. WE WILL BE MONITORING THESE FEATURE`S
CLOSELY FOR THE NEXT FIVE TO SEVEN DAYS.
Not ALL. It's 1.30 in the afternoon, here. Hello, anyway.
I think the 850 is a typo. Recent Quikscat showed a LLC ~32-33W.
Good morning
Sorry to hear that - let us know how it goes.
That blob near 38W is about 850 miles from the Cape Verde's.
That front is behind the ull that's been stalled out over the southeast. It's (along with it's upper trough) what's started the ull in motion. A front is a surface feature and the upper level low is in the upper levels thus not on that map. Most models have them combining once they pass NC but with the way danny looks I think it could be happening sooner considering he's more west than they forecasted closer to the ull.
Okay...thanks.....hadn't looked at the TWD.
leftovers... what have the local media been saying??
just a little south than models are projecting..
I agree. Maybe WS/JFV can ask the NHC when he visits them today if the latest TWO is a typo? j/k.
In all seriousness, I've looked at 94L again and again with visible this morning and it looks like the 850 distance from the Cape Verde's is legit.
Ah you are a lifesaver, thanks a lot. So the general course of the storm "should" take it away from the islands right, especially with the NW movement? It's currently quite a bit SW of the model runs so I am pretty sure that will change the whole overall look on this. Thanks a lot StormW!
He never said NW movement....Based on forecast steering layers, the disturbance should continue on a basic westerly course for the next 36 hours, with a possible short term motion to the WNW, being brought back on a slight north of west motion afterward.
Oh thank you. I understood north west haha, hey I woke up 20 minutes ago! Thanks for the clarification =)
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