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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767. slavp
Quoting NRAamy:
my magnificent purple fat folds are great at predicting the weather....when they drip sweat...it's hot outside!
Talk about Heat Index!!!! lol
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765. 786
Well I thought this was a weather blog apologies
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So far the Recon has only found surface winds around 25mph...although they haven't been in the convection to the east of the CoC yet...

They're on their way there though, so we should see if Danny has 45mph winds or not here within an hour or two.
Quoting Acemmett90:

well atleast we wont get the storm surge which is the most damaging part of the storm


A cat 5 is still a cat 5, even if we don't get the 30 foot wall of water with it.
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Quoting mikatnight:


Arc clouds! Like the Doc mentioned yesterday. I learned something!


Ha Ha. The weather keeps teaching me things too... Humility is a common theme.
Quoting NRAamy:
786...it was a joke...



Some people just don't get it...

We like you regardless of your dimensions anyways!

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786...it was a joke...

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Quoting palmbaywhoo:

just what we nedd, another tramp


Or you could use an english teacher.
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Quoting OSUWXGUY:
Still might be dry air in the mid-level as evidenced by the arc clouds to the north of the CoC


Arc clouds! Like the Doc mentioned yesterday. I learned something!
Member Since: October 18, 2005 Posts: 4 Comments: 3052
Quoting Acemmett90:

so we dont get hit


Except when one forms in the BOC or GOM. Then that front is our enemy...
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well then lets get back to the tropics

yeah, good luck with that!
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745. 786
How are the steering currents looking for the CV wave. I have heard that when a set up has been around for while it stays in place...does it look like the Caribbean will be lucky this season?

NRA no offense and sorry to burst any mans bubbles but 36-24-36 is not humanly possible. Unless one had surgery to make that possible the body simply does not grow that way - hips and shoulders are never the exact same and one would have to break some rib cages to be a 24 waist with a 36 hip. Those were the dimensions stated by the creators of the barbie doll were she human sized.
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Quoting mkmand:
now the "west wishcasters" has something to talk about again


Sad, but some folks don't feel they get the full "blog" experience unless they can call someone a ****caster. Sad.
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Quoting Dakster:


Thank you front...


haha thats good
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Does it appear to anyone else that Danny is not vertically stacked yet? Looks like the upper level circulation is trying to finally come over the lower level
Member Since: February 27, 2006 Posts: 0 Comments: 482
The African wave is organizing very nicely. We should see an orange circle by tomorrow. Bands have setup in the southern quadrant and it looks like a MLC is becoming better established.
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Quoting K8eCane:


florida people better thank that front


Most probably. Anticipating those model runs as they should get some good data to plug into the models.
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Latest obs from the Recon.

Couple things of note. This was the lowest pressure they found - 1007.2mb which is a drop of 2 since the 11AM update.

The center also moved from the 11AM position of 24.9N 70.3W to 25.0N 70.8W ( 0.1N, 0.5W) or just north of due west.

Also of interest compared to yesterday. At a slightly lower flighty height, yesterday there was a dewpoint at 1000 feet of 59F. Today at a slightly higher level 1500 feet, there was a dewpoint of 72F.

Much moister lower levels which should contribute to more instability and convection down the road. Still might be dry air in the mid-level as evidenced by the arc clouds to the north of the CoC.

Ob Time:17:48:30Z
Location: 25.033N 70.867W 958.9 mb

Flight Height:(~ 28.32 inHg) 431 meters (~ 1,414 feet)

Surface Pressure (Extrapolated) 1007.2 mb

Flight Level Winds: From 107 at 6 knots
(From the ESE at ~ 6.9 mph)

Temp at Flight Level: 22.5C(~ 72.5F)
Dewpt at Flight Level: 22.5C (~ 72.5F)
Surfing in Virginia this weekend will be better than usual!
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Quoting Acemmett90:

check your grammer
you mean "it" wasn't on porpus

Check your credentials, my concern about your grammar approval, and your spelling. And I meant exactly what I posted.

"It wasn't on purpose and WS is not a blog topic."
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Quoting Acemmett90:

personly i hope the front gets stuck


Why?
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Quoting K8eCane:


florida people better thank that front


Thanks Mr. Front.
Member Since: October 18, 2005 Posts: 4 Comments: 3052
Quoting atmoaggie:
Wow. Battle of wits between the regular operational GFS and the ensemble mean. Come on ensemble. Go. Go. Go. That would be very nice.



I guess by Sept. 10th we'll know who won... hehe.
Member Since: August 14, 2008 Posts: 4 Comments: 4932
Quoting jeffs713:
sorry for the multiple posts all. cell-phone posting does not agree with WU blogs...


I know what you are saying. Mine won't let me log into my account for some reason.
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Quoting K8eCane:


florida people better thank that front


Thank you front...
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Quoting Seastep:
For the GOM discussion, it is not the usual afternoon storms. It is associated with a front.
NAM developed something there in 12 to 24 hours.
Quoting Seastep:
For the GOM discussion, it is not the usual afternoon storms. It is associated with a front.


florida people better thank that front
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Quoting jeffs713:
i'm posting from my cell phone, and everytime i reloaded the page, it reposted it. sorry. :/


Sir Mix-a-Lot back off of the PDA. The remix isn't as catchy as the original.
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Quoting jeffs713:
i'm posting from my cell phone, and everytime i reloaded the page, it reposted it. sorry. :/


I can't get that stupid song out of my head now LOL!
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Quoting Acemmett90:

its getting old and it not funny any more this is not old though
Can somone post the WS OUT house

It wasn't on purpose and WS is not a blog topic.
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Quoting nrtiwlnvragn:
The key near term model run will be this evenings 00Z. The Gulfstream IV will be releasing dropsondes in this pattern this afternoon.....


Interesting... Seems they want to see the depth of the Cut Off Low... should be critical in the possible path of Danny.
Member Since: August 14, 2008 Posts: 4 Comments: 4932
Quoting 900MB:
Getting a little convection to the north of coc.


Does seem to be going more west than anything right now, or is it just me?


If you got time look at my entry this morning #579. Hope we are both wrong.
Member Since: July 17, 2009 Posts: 69 Comments: 25382
sorry for the multiple posts all. cell-phone posting does not agree with WU blogs...
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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.