TD 3 growing more organized

By: Dr. Jeff Masters , 8:01 PM GMT on July 22, 2010

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Tropical Depression Three is steadily organizing, and appears poised to become a much stronger storm than was forecast. Water vapor satellite loops show that the upper level low to the west of TD 3 that has been bringing high levels of wind shear to the storm is now moving faster to the west than predicted. This faster motion has resulted in a reduction in wind shear over TD 3, to a moderate 10 knots. Satellite images of TD 3 show that the storm is taking advantage of the lower shear by developing several low-level spiral bands to the north and east of the center. However, the center of circulation is still exposed to view, and dry air is still getting injected into the core of the storm from the southwest. The storm's heavy thunderstorms have not increased in intensity this afternoon, and the amount of heavy thunderstorm activity near the core of the storm is still limited. TD 3 will need to build more intense thunderstorms near its center before significant intensification can occur. TD 3 is a small storm, and surface observations in the Bahamas do not show the circulation very well. An outer rain band of TD 3 is now visible on Miami long-range radar, and a flood watch has been issued for all of South Florida. The Hurricane Hunters are in the storm at present, and have found top surface winds of 35 - 40 mph.


Figure 1. Afternoon satellite image of TD 3.

Track Forecast for TD 3
The storm is in a straightforward steering current environment, and TD 3 should progress steadily to the west-northwest through Sunday. This will bring the storm ashore over the Florida Keys or South Florida on Friday, and into the Gulf of Mexico on Saturday. The latest set of model runs from 8am EDT (12Z) foresee a track more to the north than the previous set of model runs. This increases the threat to the oil spill region, and I give a 40% chance that the oil spill region will see tropical storm force winds of 39 mph or higher this weekend. Oil recovery and relief well drilling operations should cease. If TD 3 makes a direct hit on the oil spill region as a tropical storm with 50 - 60 mph winds, it will likely drive a storm surge of 3 - 6 feet with high waves on top into the Louisiana marshlands, fouling a large area with oil. Oil would also penetrate into Lake Pontchartrain, which lies just two feet above sea level. However, the wave action of the storm will dilute the oil to some degree, which may limit the damage to the marshlands.

If you are wondering about the specific probabilities of receiving tropical storm force winds at your location, I recommend the wind probability product from NHC. The latest 5 pm probabilities of various locations getting tropical storm force winds, 39 mph or higher:

Marathon 55%
Marco Island 43%
Miami 34%
New Orleans 33%
Galveston 13%

Intensity Forecast for TD 3
The primary detriment to development of TD 3 for the next three days will be the presence of the large upper-level low to its west. If the low remains in its present location, relative to TD 3, it will bring wind shear of about 10 knots to the storm. This will allow for steady intensification of perhaps 20 mph per day, and TD 3 could be a hurricane by Sunday at that pace. However, if the upper-level low slows down a bit, relative to TD 3, more shear and dry air will affect the storm, potentially weakening it. None of the computer models is calling for TD 3 to strengthen into a hurricane, but if the shear continues at 10 knots, I expect TD 3 will become a hurricane. My low-confidence intensity forecast gives TD 3 a 40% chance of becoming a hurricane. NHC is putting the odds of TD 3 being a hurricane at 2 pm Sunday at 15% with their 5pm advisory.

98L
An area of disturbed weather (98L) has developed in the Gulf of Mexico's Bay of Campeche. This system is under a low amount of shear, 5 - 10 knots, and probably does not have enough time to organize into a tropical depression before making landfall along the Mexican coast a few hundred miles south of the Texas border on Friday.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Next update
I'll have an update in the morning. ABC World News Tonight will probably show a sound bite I did for them today, on their 6:30pm broadcast.

Jeff Masters

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Looks like Nassau is on the edge of the heavy convection now.

To tell the truth, Bonnie seems to be moving more or less long that projected path - with wobbles, of course - and pulling the deformed convection along at pretty much the same angle as we've seen since yesterday. Unless something wonderful happens to change this formation, I don't see how this system can strengthen appreciably....
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RIP Bonnie, JK. In all seriousness, Bonnie looks like it might just outrun the ULL and hit SFL as a pretty mild tropical storm. If not then it might get it's head cut off.
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Back in Oct 1999, SoFla got Hurricane Irene. Local government and mets were saying: 'oh, it's a minimal Cat 1, everyone go about your daily routine. Nothing is cancelled...blah, blah, etc.' Well, around mid day, everyone was sent home in a rush because winds were much higher than expected and flooding was everywhere. I was one of those in traffic on the xpressway, terrified as my car was shaking so bad and visibility down to zero. With Bonnie now, it's kind of like the same attitude: 'oh, it will just be some heavy rain, some gusts of wind, blah, etc.". I know it's just a TS, but sometimes intesity is worse than expected. I hope it's as benign as they are saying for i don't want to get caught in traffic on the expressway again and experience what I did that day in 1999. This time I'm in a minivan with precious cargo on board...
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Quoting redUK:
This is actually an eye.

Let's see if it can persist?

No it is not.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting redUK:
This is actually an eye.

Let's see if it can persist?

Thats not an eye.
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National Hurricane Center - 8:00 pm Advisory
TROPICAL STORM BONNIE
*Graphics Update
STORM TRACKER

ADVISORIES
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We really need an updated microwave pass right now. That would give us a better idea as to just how decoupled the low- and mid-level vorticity centers actually are.
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Right when it looks like it might have gotten away from the ULL to the west and strengthen, the one to the east is really bearing down on it. If it keeps advancing at this pace could be the demise of Bonnie. So many variables with this system. Fun one to watch.
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2161. redUK
This is actually an eye.

Let's see if it can persist?

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There are too many downcasters on here tonight, I'll be back on later. Frustrated a bit after showing maps and facts that conditions are not hostile to back up my statement and I still get pointed out wrong. You guys got wayy too much of hurrikat (stormtop) this evening.
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Quoting stormwatcher247:
The storm is NOT looking good at all. I'd be surprised if it survives.
If the system looked "SO" bad it wouldn't be receiving a T3.0 from TAFB and a T2.5 from SAB.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting stormwatcher247:
The storm is NOT looking good at all. I'd be surprised if it survives.


RIP Bonnie?
Member Since: April 26, 2009 Posts: 3 Comments: 3667
I have the center at 23.5/76.6 and I see it wrapping up...Levi, if you are still here, when it comes to a competing LLC and MLC, shouldn't the LLC win? TIA

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Quoting SouthDadeFish:
Really starting to get pinched by the ULL to the NE instead of the one to the west. Link
this almost looks as if were a late oct pattern...
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The storm is NOT looking good at all. I'd be surprised if it survives.
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Quoting SouthDadeFish:
Really starting to get pinched by the ULL to the NE instead of the one to the west. Link


Wow and the ULL to the northeast is moving down rapidly. I wouldn't be shocked if thing just gets torn apart.
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2150. Patrap
Quoting bappit:

That Bonnie is a fighter. Got to give her credit. I have never seen such will power from an atmospheric circulation.


Very CV like in Tenacity..

TS Bonnie is a Rogue lady waiting to Get Phat in a Hurry..

Hopefully she will Stay out Da french Quarter and on a Diet.
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2149. redUK
After being unimpressed earlier, it now looks to me like the ULL is moving slightly faster than than Bonnie.

Also, the last few frames on Nasa's page show some convection wrapping around the SW of the LLC (which is just SW of the MAIN convection).

Check out last few frames:

http://wwwghcc.msfc.nasa.gov/cgi-bin/post-goes


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Quoting SeniorPoppy:
It would have to have one heck of a d-max to get to 50-60 mph winds.

wowowowowowowowowowowowowowowowow calm the freak down
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
Watch the upper low at 28N from 60 to 65W. The 18z GFS suggests it could also move westward in tandem with Bonnie. Either that will destroy it, or ventilate it.
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Quoting pipelines:
I have to disagree with the claims that the mid and low level centers are decoupled. While I can see what a few are claiming is the llc moving to the south west on sat imagery, it isn't clear enough in my opinion to make any claims on.

That aside, I see no reason for the centers to become decoupled at this point in time, centers don't decouple at random, there has to be a reason for this to occur such as mountains or high levels of sheer.

Also, I've never seen an LLC become decoupled from an MLC and ejected from the convective mass at the speed the supposed LLC was ejected.


Bonnie has had a dry slot at 500 mb level for the last two days and this is enough to start the process for decoupling. This dry layer will inhibit the circulation at that level and also affect the ability for development due to the lack of convective structure through the dry layer.
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2144. bappit
Quoting centex:
Not because of strength but I'm impressed how it fights off adverse conditions and takes advantage of every little opportunity.

That Bonnie is a fighter. Got to give her credit. I have never seen such will power from an atmospheric circulation.
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Something I said last night, why are we taking those CIMMS numbers as gospel. Look at the satellite, it tells the whole story.
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It would have to have one heck of a d-max to get to 50-60 mph winds.
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Really starting to get pinched by the ULL to the NE instead of the one to the west. Link
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Quoting Tazmanian:



eye caster


No it's called ignorant pic-post casting.
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Quoting MiamiHurricanes09:
Me and CCHS are in perfect agreement that Bonnie will make landfall in south/central Miami-Dade county tomorrow as a 50-60mph storm. However, it needs to work on some stuff before reaching that threshold.


My forecast has Bonnie cliping south of Miami and just north of the Keys tomorrow.. 50-60 mph. TS
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In 4 hours we are averaging around 500 posts a hour.
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.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2135. bappit
Quoting WeatherLoverinMiami:
I was just looking at channel 7 weather guy is a idiot he is telling people that bonnie is not looking to good what is this idiot looking at

More to the point, what are you looking at?

Bonnie is getting squished. The faster the ULL moves to the west, the faster dry air surges in from the northeast. Looking dim.
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2134. Patrap
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Quoting StormHype:


A US Congressman


A husband!!!!
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Levi, Bonnie is in the middle of two very hostile locations. Wind shear is high directly to its, as a result of an enhanced pressure gradient caused by deep-layered ridge and an upper level at 60W 28N. The ULL is producing too much wind shear to its west.

Member Since: July 19, 2008 Posts: 43 Comments: 4051
2131. Patrap
GOES-13 or East is in Eclipse /Blackout
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I have to disagree with the claims that the mid and low level centers are decoupled. While I can see what a few are claiming is the llc moving to the south west on sat imagery, it isn't clear enough in my opinion to make any claims on.

That aside, I see no reason for the centers to become decoupled at this point in time, centers don't decouple at random, there has to be a reason for this to occur such as mountains or high levels of sheer.

Also, I've never seen an LLC become decoupled from an MLC and ejected from the convective mass at the speed the supposed LLC was ejected.
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Quoting SeniorPoppy:


Either way, I'm not impressed. Hostility surrounds this system. I'd be shocked if this system intensifies to even 60 mph winds.


These conditions are moving westward, Bonnie is following the favorable conditions for now, the hostile conditions to the west are moving westward with the ULL which is far away from Bonnie.
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Quoting reedzone:


Exactly, people need to just have patience lol. The ULL is far away from Bonnie enough for it to gain some strength. A 60 mph. storm for Florida is not out of the question, but gotta see how this goes tonight.
Me and CCHS are in perfect agreement that Bonnie will make landfall in south/central Miami-Dade county tomorrow as a 50-60mph storm. However, it needs to work on some stuff before reaching that threshold.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Bonnie may not be decoupled, but as I saud before, its definitely not stocked vertically either! And without it being stacked from the surface into the atmosphere, it really can't do much to strengthen.

But I must say, I don't agree with the fact that at the moment there is only 10 knots of shear!

All these shear maps being referred to do not reflect real time conditions.....

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Quoting SeniorPoppy:
We are going to go from the Florida doom-casters to the GOM-casters. Gotta love it.


How did you get off of my ignore list? Maybe I was smashed and did not save it LOL
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2124. Patrap
NEXRAD Radar
Miami, Velocity Azimuth Display Wind Profile Range 124 NMI

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x-caster
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Quoting opsman27N82W:
Grothar, US old guys need to go to bed "Danger Will Robinson" I am well prepared for two days of rain and a slight blow. X forming LOL


ummmmmmmm
Member Since: October 1, 2007 Posts: 81 Comments: 26516
2121. angiest
Quoting Tazmanian:
guys the CIMMS shear maps may be 10% off in other words the wind shear may not be that high


By the same token it could be higher. :)
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Quoting MiamiHurricanes09:
Look at the outflow and banding features, that alone should tell you that Bonnie is under favorable upper level conditions.


Exactly, people need to just have patience lol. The ULL is far away from Bonnie enough for it to gain some strength. A 60 mph. storm for Florida is not out of the question, but gotta see how this goes tonight.
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Quoting reedzone:


Even more proof that shear is not an issue! That patch of decreasing shear is moving along with Bonnie. We don't have visible so we don't know for sure if it's decoupled. It is however gewtting squashed under the high, but I dont think that will stop it from growing more later. 10 knots of shear doesn't tear apart systems and that's what Bonnies center is under per the LATEST CIMMS shear map.


Either way, I'm not impressed. Hostile conditions surround this system. I'd be shocked if this system intensifies to even 60 mph winds.
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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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