Tropical Storm Danny not impressive yet
Tropical Storm Danny is here, born from an African tropical wave that developed a closed circulation and some respectable heavy thunderstorm activity this morning. Data between 2 - 3 pm EDT from the Hurricane Hunters indicates the Danny has a central pressure of 1009 mb, and top surface winds of about 45 mph. Satellite imagery shows that Danny's circulation has gotten stretched and pulled away from the heaviest thunderstorm activity on the storm's east side. It is possible that Danny's center will reform at a different location, closer to the heaviest thunderstorms, so the model forecasts probably have a higher degree of uncertainty than usual at present. Wind shear has dropped to the low range, 5 - 10 knots. The upper-level low Danny is moving underneath has plenty of dry air in it, and this dry air is intruding into Danny's west side, keeping and heavy thunderstorm activity from developing on that side.
Figure 1. Oceanic heat content for August 25, 2009. Regions where the Sea Surface Temperature is below 80°F, or where the shallow waters of the Continental Shelf lie, do not have enough heat content to be plotted, and are shown in white colors. The oceanic heat content along the track of Tropical Storm Danny is below the threshold of 90 kJ/cm^2 typically seen with cases of rapid intensification. The storm position at 8am EDT today is given by the hurricane symbol with the "0" inside it. Subsequent hurricane symbols show the official NHC forecast points from the 11 am EDT forecast today, for 8am Thursday (24 hours), 8am Friday (48 hours), 8am Saturday (72 hours), and 8am Sunday (72 hours). The cold waters stirred up by Hurricane Bill last week will not impact Tropical Storm Danny. Image credit: RSMAS, University of Miami.
The forecast for Danny
As Danny continues to plow through the upper low, the low will weaken, but will dump dry air into the storm through Thursday afternoon, slowing down development. By Thursday night, when Danny should be several hundred miles off the coast of northern Florida, the upper-level low may be weak enough and far enough away that Danny will find itself in a region with light upper level anticyclonic winds, which would favor more rapid development. Ocean heat content (Figure 1) is high enough to support a hurricane, until Danny gets to about New Jersey's latitude. Most of the intensity models, including the GFDL, HWRF, and SHIPS model, forecast that Danny will become a hurricane by Friday. However, this favorable environment will not last long, since a strong trough of low pressure will be approaching the U.S. East Coast on Friday. This trough will bring high wind shear of 20 - 30 knots by Friday night. This trough should be strong enough to turn Danny to the north, then northeast on Saturday. The models have come into better agreement keeping Danny offshore as it passes North Carolina, though the storm is certainly capable of giving the Outer Banks a direct hit. As Danny passes North Carolina, it should start heading north-northeast, with a landfall likely Saturday afternoon or evening somewhere between Massachusetts and Nova Scotia. At that time, Danny is likely to be a strong tropical storm or weak Category 1 hurricane, with winds in the 55 - 80 mph range. The latest runs of the GFDL and GFS model have Danny tracking directly over Martha's Vineyard, where President Obama is on vacation. It will be interesting to see if the president stays on the island for Danny.
For those of you wondering about specific probabilities of getting tropical storm force or hurricane force winds, consult the NHC Wind Probability Product.
Figure 2. Tropical wave newly emerged from the coast of Africa, with some potential for development.
Elsewhere in the Atlantic
A well-organized tropical wave has exited the coast of Africa, and lies a few hundred miles southeast of the Cape Verdes Islands. None of the models are gung-ho about developing this wave, but shear is low, 10 knots, and waters are warm enough to support 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 some slow development of this wave as it moves westward over the next few days. NHC is giving this system a low (less than 30% chance) of developing into a tropical depression by Friday afternoon.
I'll have an update Thursday.
Jeff Masters
Reader Comments
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what are you talking about????
atmoaggie has never been banned and he says that sort of stuff all the time.
(3rd person thrown in just to irritate jeffs a little extra)
The blob on the bottom right
LOL Aquak9
At least the person behind the mask seems to have a sense of humor. I still liked the political impersonators best. I wonder why barackobama hasn't posted this year?
I love it when they get all technical.
(His thoughts on Danny)
Discussion
Tropical Storm Danny is the only major concern in this outlook. Danny has slowed and continued to move west-northwestward from a position to the immediate northeast of the Turks and Caicos. Satellite imagery shows that the tropical storm has a sheared presentation (convection entirely to the right of the center of circulation), and still has not full absorbed the remnant TUTT signature to its north and west. That event should happen, however, within another 12 - 24 hours, and some modest strengthening is likely over the warm waters adjacent to the Gulf Stream.
That said, the chances for Danny to become a hurricane are marginal at best. The frontal structure and south-southwest flow aloft off of the Eastern Seaboard will turn the tropical storm northward, and the convective shield may once again be displaced, with exposure of the center along its southern flanks. While quite a few of the tropical forecast schemes make Danny a Category 1 storm, I believe that a 60 to 70 mph wind field is more probable. Not only will there be a frontal structure with some shear involved, questions abound concerning the approach of a strong trough from the Great Plains and Midwest by Friday.
There are three viable track/intensity scenarios in play. One is that Danny never strengthens, and gets sucked up into the oncoming frontal structure. That would mean a barrage of heavy rain and maybe some severe thunderstorms in a belt from C, E NC into NS (as far west as eastern slopes of the Appalachian Mountains). The other is a non-phase interaction where Danny keeps its current intensity (or maybe slightly stronger), and throws moisture over the stalled thermal transition. This brings torrential downpours along and to the right of Interstate 95 from the Washington - New Bern NC vicinity through the major urban areas into ME and NS. The third possibility: Danny indeed become a hurricane and never gets pulled into the trough, and brings heavy rain and wind to only Cape Cod and the MA Islands as well as NS and NL in Canada. As of now, I think that the idea projected by the NAM and UKMET versions is the most workable (see graphic); a big rain event with only a few wind-related issues along the Atlantic Coastal Plain from E NC into NS.
Much cooler air will become entrained into Danny by Sunday as the storm heads into Newfoundland. I believe that there is a fair chance that the storm becomes extratropical and that wind gusts will pick up over the Northeast and Maritime Provinces as we start the new week.
I think its the morning when you should avoid these posts. Seems to upset the early shift.
Alright, lets get back to Danny now.
Florida or Georgia: 6%
Carolinas: 42%
Out to sea: 80%
Nova Scotia, Newfoundland other areas around there: 64%
AllStar17
Give us some more of your great graphics!
alright not to sound like a smart ass.... but thats way more than 100% hahaha
Laundry, dinner, snack of cheese whiz and crackers, prepare for hurricane, sleep.
A TROPICAL WAVE LOCATED OVER THE FAR EASTERN ATLANTIC CONTINUES TO
PRODUCE AN AREA OF DISORGANIZED SHOWERS AND THUNDERSTORMS SOUTH OF
THE CAPE VERDE ISLANDS. DEVELOPMENT OF THIS SYSTEM WILL LIKELY BE
SLOW TO OCCUR AS IT MOVES WESTWARD AT 10 TO 15 MPH OVER THE NEXT
COUPLE OF DAYS. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
... there is no ''if any'' in there
LOL!!!!
bombing out! hahaha, thats suprising to me... i bet its 55mph at 11pm
got any science to back that up? Id like to hear it
agrree that ull has its eyes for fla and still pulling danny along all day when is this n turn suppose to happen acording to the nhc
Taking the consensus approach a step farther, "corrected" consensus models assign different weights to each member model in an attempt to account for biases of each individual member model. One limitation of the "corrected" consensus technique occurs when the past performance of the member models does not accurately represent their present performance (e.g., if major changes are made to a member model between successive hurricane seasons). Some of the commonly used "corrected" consensus forecasts at NHC include FSSE, TVCC, and TCCN.
Technical Summary of the National Hurricane Center Track and Intensity Models
Sigh...you said the same thing about Bill. I could say IMO its going to Michigan but I'm not cause no facts suggest that.
Intermediate advisories are only issued when watches or warnings are in effect.
I'm not sure but if this keeps this way through tomorrow, it won't be good for the East coast.
No problem, give me a few! :)
south carolina has a very slim chance of being hit.
Now why would you want to irritate me? Just because I tried to make a somewhat silly post that sounded a lot better in my head than it did once I typed it...
The wind speed isn't special, but the direction is swinging to those coming from SSW...as should be. Could be a sign if it sticks.
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