Tropical Storm Danny likely to be named today

By: Dr. Jeff Masters , 1:25 PM GMT on August 26, 2009

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First-light satellite images of the tropical wave (92L) a few hundred miles northeast of the Bahama Islands show that the system has developed an organized surface circulation, and 92L will likely be named Tropical Storm Danny later today. This morning's QuikSCAT pass confirms the presence of a surface circulation, and the satellite saw top winds of 50 mph in a cluster of thunderstorms well east of the center. Wind shear has dropped to the moderate range, 10 - 15 knots. The upper-level low 92L is moving underneath has plenty of dry air in it, and the upper low is injecting this dry air into 92L's west side, keeping and heavy thunderstorm activity from developing on that side. The Hurricane Hunters are in 92L, and have found surface winds up to 57 mph so far this morning. NHC continues to give 92L a high (greater than 50% chance) of developing into a tropical depression by Thursday afternoon.


Figure 1. Water vapor satellite image from 8:15 am EDT 8/26/09 showing dry air associated with an upper-level low pressure system to the west of 92L's center of circulation. Image credit: NOAA/SSD.

The forecast for 92L
As 92L continues to plow through the upper low, the low will weaken, and wind shear is expected to decline to the low range, 5 - 10 knots, by tonight. However, the upper-level low will continue to dump dry, cold air into 92L through Thursday afternoon, slowing down development. By Thursday night, when 92L should be several hundred miles off the coast of northern Florida, the upper-level low may be weak enough and far enough away that 92L will find itself in a region with light upper level anticyclonic winds, which would favor more rapid development. Most of the intensity models, including the GFDL, HWRF, and SHIPS model, forecast that 92L 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 92L to the north. The models have come into better agreement keeping 92L offshore as it passes North Carolina, though the storm is certainly capable of giving the Outer Banks a direct hit. As 92L passes North Carolina, it should start heading north-northeast, with a second landfall likely Saturday night or Sunday morning somewhere between Massachusetts and Nova Scotia. At that time, 92L is likely to be a strong tropical storm or weak Category 1 hurricane, with winds in the 55 - 80 mph range. It currently appears that 92L will not bring tropical storm-force winds to the Bahamas or to Florida.

Elsewhere in the Atlantic
The models have been inconsistently predicting formation of several tropical waves coming off the coast of Africa over the next week, and I am going to stop mentioning these forecasts until we get two models predicting the same thing, several model runs in a row.

I'll have an update later today.

Jeff Masters

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Quoting Chicklit:

looking better and better
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Oh my, the trough up north flattened.
Good luck East Coast.

Sat Image
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DannyboyLink
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Quoting iluvjess:
COC seems to be seperating from the convection. They seem to be moving in different directions.


I believe the is the upper level low seperating from Danny
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Quoting Autistic2:
Will NE Florida catch any rain from Danny? We could use a little.
Youll get more rain from the stalled front, rather than danny.
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AOI

AOI

AOI

AOI

Member Since: October 1, 2007 Posts: 81 Comments: 26516
I'm still having a hard time trusting the models on this one...Danny isn't overly vertical, especially on his west and south sides. Isn't it logical to assume his westward (or nearly westward) movement for atleast 24-36 hours until more convection builds and is steered more northerly?
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Quoting StSimonsIslandGAGuy:
Interesting radar. Quite unusual to see convection building up over the open water in the middle of the afternoon---that usually happens at night.

There seems to be a boundary from 100 miles east of Savannah running SSW to to Daytona Beach, shifting slowly west. It has the appearance of a tropical wave, although it may be a kind of boundary of the air mass surrounding Danny.



Actually that's not uncommon, if there unstable air, this can happen.
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Will NE Florida catch any rain from Danny? We could use a little.
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Member Since: September 23, 2005 Posts: 15 Comments: 11346
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 26th day of the month at 18:49Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 307)
Storm Number & Year: 05L in 2009
Storm Name: Danny (flight originating in the North Atlantic basin)
Mission Number: 2
Observation Number: 04
A. Time of Center Fix: 26th day of the month at 17:54:10Z
B. Center Fix Coordinates: 25°00'N 70°50'W (25.N 70.8333W) (View map)
B. Center Fix Location: 408 miles (656 km) to the E (91°) from Nassau, Bahamas.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 16kts (~ 18.4mph)
E. Location of the Estimated Maximum Surface Wind: 6 nautical miles (7 statute miles) to the N (359°) of center fix
F. Maximum Flight Level Wind Inbound: From 67° at 15kts (From the ENE at ~ 17.3mph)
G. Location of Maximum Flight Level Wind Inbound: 8 nautical miles (9 statute miles) to the NNE (12°) of center fix
H. Minimum Sea Level Pressure: 1009mb (29.80 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23°C (73°F) at a pressure alt. of 465m (1,526ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 23°C (73°F) at a pressure alt. of 454m (1,490ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 23°C (73°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind and Pressure
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 10 nautical miles
Remarks Section - Remarks That Were Decoded...
Maximum Flight Level Wind: 49kts (~ 56.4mph) in the northeast quadrant at 18:38:30Z
Maximum Flight Level Wind Outbound: 49kts (~ 56.4mph) in the northeast quadrant at 18:38:30Z
Remarks Section - Additional Remarks...
SLP EXTRAP FROM BELOW 1500 FT
Member Since: September 23, 2005 Posts: 15 Comments: 11346
Quoting justalurker:


though it might be for others.LOL


Yeah, it's a real concern for Carolina and the NE. Not so much for me in Florida.
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Ole Danny boy is racing right along,any idea when he suppose to slow down?
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COC seems to be seperating from the convection. They seem to be moving in different directions.
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Quoting CaneWarning:
I see the tropics are becoming active again. I have my eye on that African wave. Danny isn't so concerning to me.


though it might be for others.LOL
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Quoting atmoaggie:
test

Is this thing on?
Post apparently sent to Japanese small engine repair blog (where Floodman says they go)

Really neato image:


Morning glory clouds

"What causes these long, strange clouds? No one is sure. A rare type of cloud known as a Morning Glory cloud can stretch 1,000 kilometers long and occur at altitudes up to two kilometers high. Although similar roll clouds have been seen at specific places across the world, the ones over Burketown, Queensland Australia occur predictably every spring. Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height. These tubes and surrounding air could cause dangerous turbulence for airplanes when clear. Morning Glory clouds can reportedly achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind."
http://antwrp.gsfc.nasa.gov/apod/ap090824.html


Great pic. Looks fake because its so unusual.
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where is the COC located now?
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I see the tropics are becoming active again. I have my eye on that African wave. Danny isn't so concerning to me.
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Quoting tornadodude:


thanks, so does anyone have a good recent satellite of danny?




trying to start thunderstorms on the western side.
Member Since: September 6, 2007 Posts: 0 Comments: 6706
Does anyone have a link for download to allow google earth to follow the Hurricane Hunters live for MAC?
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Quoting StSimonsIslandGAGuy:


Chris Landsea made that point in comparing the 1933 and 2005 seasons (1933 was the previous record holder for the most storms in a season)
This map expresses it quite well, I think:



St. Simons,
Very interesting graphic. Thanks.
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12 ECMWF... back on board with possible 94L or TS Erika.
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Quoting Seastep:


It's to gather data on the front for model input.


O.K., still a little unbelievable, but that's just the way I am.
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Quoting atmoaggie:
test

Is this thing on?


You're on the air lol.
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Quoting StormSurgeon:


What?


Hehe... as Seastep mentioned... the Gulfstream IV-SP is sampling the atmosphere in the GOM and W ATL region for input on computer models later today...most likely by 00Z.
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838. IKE
Quoting tramp96:


Can you show your work on that please
tia


I'm basing it on computer models.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting StSimonsIslandGAGuy:
I like the HWRF track for Danny, although the way the GFDL and HWRF continue deepening the storm north of Cape Hatteras until it reaches the latitude of New England seems unrealistic.

If the pressure goes below 970 mb, I'll be moderately surprised.

No real thoughts on our Cape Verde wave. This year since it's been so troughy all summer, I think it likely that whatever forms will be picked up and out, with only the northern Leewards and Bermuda at risk.

I think the GFDL and HWRF are bombing Danny out off the mid-Atlantic coast because of the storm's projected path over the Gulf Stream, and also the topography of the land which will cause the storm to be compressed on the western side. The GFDL and HWRF have always overestimated that, (they did the same thing for Dolly, IIRC), but it is a factor that needs to be accounted for.
Member Since: August 3, 2008 Posts: 16 Comments: 5891
test

Is this thing on?
Post apparently sent to Japanese small engine repair blog (where Floodman says they go)

Really neato image:


Morning glory clouds

"What causes these long, strange clouds? No one is sure. A rare type of cloud known as a Morning Glory cloud can stretch 1,000 kilometers long and occur at altitudes up to two kilometers high. Although similar roll clouds have been seen at specific places across the world, the ones over Burketown, Queensland Australia occur predictably every spring. Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height. These tubes and surrounding air could cause dangerous turbulence for airplanes when clear. Morning Glory clouds can reportedly achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind."
http://antwrp.gsfc.nasa.gov/apod/ap090824.html
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Any possibility Danny could become a strong cat 1 before getting close/brushing the Outer Banks NC. Not much time to prepare if so.
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833. IKE
12Z ECMWF
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting StormSurgeon:


What?


It's to gather data on the front for model input.
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Even the very bullish CMC is showing a very asymmetrical cyclone.
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Quoting WxLogic:
GIV starting to make its drops on the GOM...


What?
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I see we have Danny at 2 p.m.
"1159 AM EDT WED AUG 26 2009
THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA...

INCREASING LONG PERIOD SWELLS FROM TROPICAL STORM DANNY WELL EAST OF THE BAHAMAS WILL GENERATE A HIGH RIP CURRENT RISK THURSDAY AND FRIDAY."

A 54 year old man died in the surf here last week during Bill's passage. Hopefully, swimmers will heed the warnings this week, although I don't think there are Lifeguards down in Bethune Beach where he was body surfing.
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Quoting nrtiwlnvragn:
Danny 18Z SHIPS indicates significant shear after 48 hours.


Not enough time to strengthen... but once it becomes extratropical then that's another story...
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819.


Yes, the A/B high is forecast to sprawl westward, holding back any significant northward movement in the near to mid term.

As for the other half of your comment... I enjoy the levity that silly comments bring here. Helps break up the "doom and gloom" that hurricanes bring to many of us.
Member Since: August 3, 2008 Posts: 16 Comments: 5891
Quoting seminolesfan:
It looks like the retrograding cyclone (cold core) over MS heading into LA is hanging up the trough.

Link


I saw that earlier and wondered why nobody mentioned it. Kind of an odd entity really!
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well, ill be back on later, i need to assemble my futon ha ;) take it easy, and try to stay on t(r)opic!
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Latest Recon Data finding surface winds supportive of the current 45 mph intensity, with possible support for raising it to 50mph.

Sample ob:

Flight Level: 49 knots(~ 56.3 mph)
SMFR Surface:42 knots(~ 48.3 mph)

There were several obs all showing 48mph surface winds from the SMFR, and the flight level adjusted to the surface winds also fall in the 45-48mph range.
How good are the data for that fifty-year average, though?

NHC recently issued a paper pointing out that the increase in the number of short-lived storms and storms that don't make landfall is a statistical artifact: better data gathering (especially but not only satellites) means we see more of the storms that form.
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Danny 18Z SHIPS indicates significant shear after 48 hours.
Member Since: September 23, 2005 Posts: 15 Comments: 11346
819. 786
807. Finally!

So the steering currents could bring this West? Is the high forecast to stengthen then?
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well thank God this is no way shape or form the next "big one"
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Quoting OSUWXGUY:


Yeah...StormW, the NHC, and most of the models show only slow strengthening over the next 24-36 hours as upper level conditions (specifically a trough axis) are not overly favorable for Danny.

On Friday, there is a brief window where some ridging is forecast to build in overtop Danny which should allow the convection to surround the circulation and let the storm become vertically stacked over very warm water. It is during this 24 hour that will really determing how strong Danny becomes.

If it is able to take advantage of this window, then it could easily become a category 1 or 2 hurricane. If not, then it will likely stay as a strong tropical storm on it way north.

Note: Intensity forecast are notoriously inaccurate in general. If you live along the East Coast, watch the weather closely over the next 24 hours and be prepared to take the appropriate actions if necessary.


thanks, the only reason that I'm asking is that i have a summer house in north carolina, and dont know if i should drive up from florida to board up..cat 1 maybe but 2 definitely. thanks for the information..check back with you later on another opinion.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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