Season's first tropical depression forms

By: Dr. Jeff Masters , 3:43 PM GMT on May 28, 2009

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Nature is jumping the gun a bit this year, with the season's first tropical depression forming four days before the official start to hurricane season. The area of disturbed weather (91L) that we've been watching, about 250 miles east-northeast of Cape Hatteras, North Carolina, has developed enough heavy thunderstorm activity and spin to be classified as a tropical depression. QuikSCAT imagery from last night revealed a closed surface circulation, but top winds of only 20 - 25 mph. Satellite estimates (using a cloud pattern recognition method called the "Dvorak" technique) were saying this was a tropical depression this morning, though, so the NHC elected to upgrade the system.

The disturbance is over the relatively warm waters of the Gulf Stream (25°C) and has wind shear of 5 - 10 knots over it, and these conditions are marginally favorable for some slow development to occur until Friday, when the system will likely move over waters too cold to support intensification. TD One is not a threat to any land areas. I give the storm a 60% chance of becoming Tropical Storm Ana.


Figure 1. Latest satellite image of TD One.

Is the formation of TD One a harbinger of an active hurricane season?
Probably not. Early season storms occurring near the U.S. coast have not been shown to be correlated with an active main portion of hurricane season during August - October. However, the situation is different if we start getting June and July storms in the deep tropics between Africa and the Lesser Antilles Islands. This was the case last year, when the formation of Hurricane Bertha in the deep tropics in July presaged an active 2008 hurricane season. According to the Hurricane FAQ, "as shown in (Goldenberg 2000), if one looks only at the June-July Atlantic tropical storms and hurricanes occurring south of 22°N and east of 77°W (the eastern portion of the Main Development Region [MDR] for Atlantic hurricanes), there is a strong association with activity for the remainder of the year. According to the data from 1944-1999, total overall Atlantic activity for years that had a tropical storm or hurricane form in this region during June and July have been at least average and often times above average. So it could be said that a June/July storm in this region is pretty much a "sufficient" condition for a year to produce at least average activity."

Portlight.org offering relief to Florida flood victims
Tropical disturbance 90L dropped as much as two feet of rain over Northeastern Florida last week, causing severe flooding. In Volusia County, at least 1500 homes were damaged by the flooding, and many of these were in low-income housing projects where the residents did not have flood insurance. Portlight Strategies, Inc., is now working to assist in this area by providing durable medical equipment to the disabled, elderly, or injured that have lost equipment due to the flooding. Equipment will also be provided to local shelters and other organizations working with flood victims. To help out, visit the Portlight disaster relief blog..


Figure 2. Rainfall amounts over Florida for the two weeks ending on May 27, 2009. Images credit: NOAA.

Jeff Masters

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Quoting GeoffreyWPB:
Why are some of you so adamant at getting TD 1 named Ana? It’s like an obsession.


Because they want Bastard's forecast busted.
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NHC is not saving anything. They have a plethora of names to use.
Member Since: October 28, 2006 Posts: 57 Comments: 30285
Quoting antonio28:
Guys, NHC are saving the names for the real storms.


I do not understand the saving names thing. They have unlimited names if it qualifies as a TS they should name it period
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01L High-Resolution Quicksat
Member Since: October 28, 2006 Posts: 57 Comments: 30285
The Planet neither Blogs nor watches TWC or the Local news I always say..

Names,smames..impact from whatever it is counts. Period.

Allison was a TS and Had its name retired,but folks remember the Storm either way
Member Since: July 3, 2005 Posts: 423 Comments: 127874
Guys, NHC are saving the names for the real storms.
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Why are some of you so adamant at getting TD 1 named Ana? It’s like an obsession.
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The Dvorak Technique Explained

The Dvorak technique is a method using enhanced Infrared and/or visible satellite imagery to quantitatively estimate the intensity of a tropical system. Cloud patterns in satellite imagery normally show an indication of cyclogenesis before the storm reaches tropical storm intensity. Indications of continued development and/or weakening can also be found in the cloud features. Using these features, the pattern formed by the clouds of a tropical cyclone, expected systematic development, and a series of rules, an intensity analysis and forecast can be made. This information is then standardized into an intensity code.
Member Since: July 3, 2005 Posts: 423 Comments: 127874
can someone post the link to the T numbers? I lost it
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Quoting GeoffreyWPB:


E-mail the NHC and tell them the next storm should be named Claudette


I'm tempted to.
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Quoting nrtiwlnvragn:


TAFB still has it at 2.0 as of 7:45 PM


I'm just talking about the reports that Drak had.
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Quoting KEHCharleston:
I still think I should get half credit for May 23rd, shoulda/woulda/coulda Ana (90L).


Well, its kinda like taking the start date of Hur season back to 5-15. The stats don't provide, an over 50% of the time occurance, justification yet. But, for you we will give you half credit :P

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WHAT? TD#1 boy did I just lose a bet.

So what now (or little later) Ana?

Was hoping for this to be the most boring season ever (I think we've (all of us in the atlantic) had enough)
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Quoting weatherblog:
Just an observation here, technically if they decided to name 90L (which I think they should've) we would be talking about Bill.

So, in retrospect, we had two named storms in May this year.


E-mail the NHC and tell them the next storm should be named Claudette
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Quoting hurricanemaniac123:
I think TD 1 will be named Ana at 11pm because the Dvorak scale says it's 2.5 which is TS.


TAFB still has it at 2.0 as of 7:45 PM
Member Since: September 23, 2005 Posts: 14 Comments: 11112
Quoting CybrTeddy:
Typical RIP calls.
-facepalm- How many times does it have to happen to slap us in the face in the morning? 90L, Pre-TD-1, Paloma, Gustav, I can go on, Dean too.


Just calling it as I see it. This storm won't last much longer even if it does develop.
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Just an observation here, technically if they decided to name 90L (which I think they should've) we would be talking about Bill.

So, in retrospect, we had two named storms in May this year.
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If TD 1 does not become Ana...there will be no named storms in May!
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Typical RIP calls.
-facepalm- How many times does it have to happen to slap us in the face in the morning? 90L, Pre-TD-1, Paloma, Gustav, I can go on, Dean too.
Member Since: July 8, 2005 Posts: 259 Comments: 23921
I think TD 1 will be named Ana at 11pm because the Dvorak scale says it's 2.5 which is TS.
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Shear is dropping east of Florida, north of Haiti, and in the GOM. I would keep an eye out for another invest in the next couple of days...

It's just a gut feeling.
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Quoting Ossqss:
BTW, our contest has Keeper up to bat today and CaneAddict and Presslord (trouble) on deck tomorrow.


I still think I should get half credit for May 23rd, shoulda/woulda/coulda Ana (90L).
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Out till later.
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Quoting Patrap:




StormW did a recent entry on Tropical ACRONYM's


Thanks Pat, that is some great info from his blog and worth a look for sure.

However, the closest I could get is>

PDO: Pacific Decadal Oscillation


Same letters, but different.

Perhaps she meant something different?


BTW, our contest has Keeper up to bat today and CaneAddict and Presslord (trouble) on deck tomorrow.


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GFS long range shear


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377. Skyepony (Mod)
Shear tendency is interesting. Dropping sw of Florida pretty good. Also looks like TD1 may be headed east toward another spot of falling shear. It certainly hasn't followed it's forecast points well.



Ike got it..Plan of Day. I don't check every single day but I've never caught them not put one out before.

Oss~ feel free to e-mail me any steller finds on that.
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Quoting Levi32:


Chris got shaved...


He got castrated.
Member Since: October 28, 2006 Posts: 57 Comments: 30285
...furthermore...depression is hardly confined to the tropics....What about all the other people around the world who deal with depression?!?!?!?!
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When I get really depressed,The wife usually will post advisories to the Family via text messages.
Member Since: July 3, 2005 Posts: 423 Comments: 127874
ya know...the tragedy here is...medical science has evolved to a point where depression can be treated...I mean...we sit around here wringing our hands about depression...but with the right medication...and, sometimes therapy, there's great hope....
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372. IKE
Quoting Levi32:


Chris got shaved...


Big-time.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:


LOL!


Chris got shaved...
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Quoting Ossqss:


Thanks Ike, I am a nubie :) , but will only ask once.

I wish we had a tropical weather acronym link --- LoL




StormW did a recent entry on Tropical ACRONYM's
Member Since: July 3, 2005 Posts: 423 Comments: 127874
Good evening all...this depression will be remembered one way or another...

- holds a new record for the farthest north a tropical cyclone has formed before June 1st...159 year old record.
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368. IKE
Quoting Drakoen:
LOL


LOL!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
RIP TD#1
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I want this to be named just so I can get past Ana and go to Bill.

I think the name Ana is starting to get boring...
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Quoting IKE:


Plan-Of-Day....for Aircraft Reconnaissance Plan of the Day


Thanks Ike, I am a nubie :) , but will only ask once.

I wish we had a tropical weather acronym link --- LoL
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Quoting Drakoen:


I'll hold my tongue until the 11:00pm advisory. I didn't think 91L would become a TD and look what happened...


Lol same here. If they were gonna upgrade it though it should have been back when it really was a TS and not now when it's not anymore.
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CI# /Pressure/ Vmax
2.5 /1005.0mb/ 35.0kt


Final T# Adj T# Raw T#
(3hr avg)
2.5 2.8 3.0

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : +13.1C Cloud Region Temp : -16.5C

Scene Type : SHEAR (0.29^ TO DG)

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.5T/hour
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
Member Since: October 28, 2006 Posts: 57 Comments: 30285
LOL
Member Since: October 28, 2006 Posts: 57 Comments: 30285
Quoting WPBHurricane05:
The 18UTC run of the GFS has my June tropical disturbance headed for Florida. Link


That doesn't guarantee anything, although MJO pulses are expected to increase about 10 days from now.





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Quoting Levi32:
Doesn't look like we'll have Ana.


I'll hold my tongue until the 11:00pm advisory. I didn't think 91L would become a TD and look what happened...
Member Since: October 28, 2006 Posts: 57 Comments: 30285
Quoting WPBHurricane05:


Uh oh...are we about to have a Chris redux??


Of sorts yes, not as rapid or as pronounced though.
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Still holding on to the possibility of Ana until the final advisory is issued.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting Levi32:
Looks like the whole convective mass is about to slide right off the plate. Wind shear is about to expose the LLC on the NW side, and the mid-level feature with associated thunderstorms will move off in another direction.

Visible Loop


Uh oh...are we about to have a Chris redux??
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting theFatherofNature:
Anyone know any good schools to go to to study atmospheric sciences(mainly hurricanes).

I'd like to know that too, I know Penn State has an online meteorology course, I'm taking it online over the summer. I think Florida has good meteorology colleges too but I think I'm assuming that because it get's hit by the most hurricanes. Hope I was helpful, Goodnight.
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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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