Bonnie barely alive

By: Dr. Jeff Masters , 12:58 PM GMT on July 24, 2010

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Tropical Depression Bonnie is barely clinging to life. Wind shear of 25 knots and dry air from an upper-level low pressure system over the Gulf of Mexico are taking their toll on Bonnie, which is now just a swirl of low clouds accompanied by a small clump of heavy thunderstorms on the north side of the center of circulation. These thunderstorms are now visible on New Orleans long range radar, and will arrive in coastal Louisiana early this afternoon, well ahead of the center. The Hurricane Hunters are in Bonnie, and have found a much weaker storm with top winds of just 30 mph.


Figure 1. Morning satellite image of Tropical Depression Bonnie. At the time, Bonnie had sustained winds of 30 mph.

Forecast for Bonnie
The current NHC forecast for Bonnie looks good, with the storm making landfall in Louisiana near 9pm CDT Saturday night. According to the latest tide information, this will be near the time of low tide. This will result in much less oil entering the Louisiana marshlands than occurred during Hurricane Alex in June. That storm brought a storm surge of 2 - 4 feet and sustained winds of 20 - 30 mph that lasted for several days, including several high tide cycles. Bonnie will be lucky to be a tropical depression at landfall, and should only create a storm surge of 1 - 2 feet that will come at low tide. This will result in a storm tide level that will inundate land to at most one foot above ground level.

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

Elsewhere in the tropics
There are no other threat areas of concern today. The only model calling for possible tropical development in the next week is the NOGAPS model, which predicts a strong tropical disturbance could form off the coast of Nicaragua in the Southwest Caribbean about a week from now.

Next update
The next updates will be by wunderground meteorologists Rob Carver and Shaun Tanner. I'm taking advantage of a break in the tropical action to take a few days away. I'll be back blogging on Friday, at the latest.

Jeff Masters

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rain looks like its almost here
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Quoting MechEngMet:
What the heck is that brewing up behind Bonnie?

What the heck is that in the south Caribbean?

What the heck is that in the BOC? (Yes there are some west winds there! Check the buoy data posted above.)


The thing behind Bonnie and the thing in the south Caribbean are the same tropical wave that is propagating westward underneath an upper low. If convection continues to go off it may be able to warm the upper atmosphere and cause a problem. For now it is ill-defined at the surface and is not an imminent threat.

The thing in the BOC is a trough of low pressure being ventilated by an upper low to its north, and steering currents slowly pushing this inland will keep it from feeding back and developing. This is the 2nd feature in the last few days that would have been a named storm if it had another day over water.
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979. SLU
Quoting Levi32:


Bonnie was centered up around 18N in the eastern Atlantic when she was a naked wave that came off Africa.


That's true. I suspect the new wave will behave in a similar manner with all the dry air around. It might start to gain convection around 45 - 50W so it needs to be watched. The wave before Bonnie behaved very similarly too and then it blew up at 60W as it came under the influence of the TUTT.
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Quoting SLU:
Something which is very worrying is the overall pattern so far which has shown a liking for westward moving systems.



Take for example the wave that's about to emerge off Africa. It emerges at about 16N yet still it is predicted to move westwards across the Atlantic into the Caribbean and end up east of Nicaragua where it begins to develop. Normally a wave emerging that far north would recurve or end up north of the Bahamas similar to the pre-Bonnie tropical wave. The CMC also shows a south of due west motion.





Quick question - I see that the propogation of these waves is generally w to wnw in what is anticipated to be a NAO environment.(according to ralieghwx ecmwf forecast)

Will they tend toward a more poleward bias in a -NAO?

Just attempting to gain some knoweldge here! TIA.
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From MH09:

"I've been analyzing the trof of low pressure in the Bay of Campeche and it is looking just a little bit promising. Convection associated with it seems to be sustained by the ULL to the north providing ventilation. Looking at vorticity and satellite imagery it looks to me that an area of low pressure may be trying to form. I'll be monitoring the situation and will be on the blog tomorrow morning after my ban ends."
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What the heck is that brewing up behind Bonnie?

What the heck is that in the south Caribbean?

What the heck is that in the BOC? (Yes there are some west winds there! Check the buoy data posted above.)
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Quoting Patrap:

"Lil by lil..I can Breathe again,now"



thank you for the lil' bit of culture thrown in there
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Quoting hydrus:
The GEM model has a low moving across the Yucatan channel, then the Gulf of Mexico and into the same region where Alex made landfall.......Link


Yeah that would be the tropical wave currently over eastern Cuba and extending down into the Caribbean. It's something to watch for.
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Quoting wxgeek1976:
What's the difference between a tropical depression and a remnant low? Bonnie's not going to become anything dangerous, but looks better than Danny did half the time he had a name.


A tropical depression has to have a certain amount of organization and deep convection. Often closed lows that develop in the tropics will be at TD status, but weakening tropical cyclones can degenerate into remnant lows even though the circulation may still be closed.
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Im thinking the ULL is strong enough to pull the BOC system along the coast, anybody else see that as a possibility.
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Quoting SLU:
Something which is very worrying is the overall pattern so far which has shown a liking for westward moving systems.



Take for example the wave that's about to emerge off Africa. It emerges at about 16N yet still it is predicted to move westwards across the Atlantic into the Caribbean and end up east of Nicaragua where it begins to develop. Normally a wave emerging that far north would recurve or end up north of the Bahamas similar to the pre-Bonnie tropical wave. The CMC also shows a south of due west motion.





Bonnie was centered up around 18N in the eastern Atlantic when she was a naked wave that came off Africa.
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"Lil by lil..I can Breathe again,now"

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Quoting plywoodstatenative:
Levi, whats that feature just off the coast of Yucatan?


There's nothing near the Yucatan lol.
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Quoting wxgeek1976:
What's the difference between a tropical depression and a remnant low? Bonnie's not going to become anything dangerous, but looks better than Danny did half the time he had a name.


A remnant low is just a disorganized area of low pressure at the surface.
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Quoting RedStickCasterette:


I am in Baton Rouge (red stick). Moved back here from the Houston area after being there for many years.

Austin is a pretty area. Love wildflowers!
I used to live in Houston too. I agree - cool place to live esp as a musician. Husband's mom loves the wildflowers here.

Good to know -wasn't sure if Aoi was near TX/MX
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Agreed SLU so far WNW is a common movement this year.
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960. xcool


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Quoting MrstormX:
Bonnie was a very minimal storm, but it should make a good Wikipedia article.


A short one at that.
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958. SLU
Something which is very worrying is the overall pattern so far which has shown a liking for westward moving systems.



Take for example the wave that's about to emerge off Africa. It emerges at about 16N yet still it is predicted to move westwards across the Atlantic into the Caribbean and end up east of Nicaragua where it begins to develop. Normally a wave emerging that far north would recurve or end up north of the Bahamas similar to the pre-Bonnie tropical wave. The CMC also shows a south of due west motion.



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I never thought about it like that before but Baton Rouge is red stick....cute...LOL
Member Since: May 28, 2008 Posts: 38 Comments: 5303
Bonnie was a very minimal storm, but it should make a good Wikipedia article.
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Quoting Patrap:
Red,,"Rouge"

Stick,, "Baton"



Ha, figured more would get it but I guess unless one is from this area, perhaps not.

I chose that name thinking it would be known, also everyone was doing the "caster" list at the time.

Silly me...
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Levi, whats that feature just off the coast of Yucatan?
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Quoting Levi32:


Agree, but it does have presence at the surface. A tight vort max at 850mb has strengthened today.

The GEM model has a low moving across the Yucatan channel, then the Gulf of Mexico and into the same region where Alex made landfall.......Link
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948. xcool
I wouldn't be suprised see 99L BOC IMO IF
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Quoting AustinTXWeather:
Redstick.. where r u located? Getting caught up on Ali. Thx :)


I am in Baton Rouge (red stick). Moved back here from the Houston area after being there for many years.

Austin is a pretty area. Love wildflowers!
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They are starting to resume the oil clean up again. I guess Bonnie was DOA.
Member Since: May 28, 2008 Posts: 38 Comments: 5303
Red,,"Rouge"

Stick,, "Baton"

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944. xcool
RedStickCasterette /lol
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Quoting atmosweather:


Looking at visible imagery...a broad low pressure center may be trying to form around 22N 96.5W. It has definitely increased in organization since this morning but with the ULL about to move out to the N it will be drifting W-ward...I be surprised if anything developed.

roughly where I saw as well
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Quoting RedStickCasterette:


Thanks xcool, I will.
Redstick.. where r u located? Getting caught up on Ali. Thx :)
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941. xcool




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Quoting Levi32:


Same here, I've pretty much dismissed it as a development threat, but geez, yet more rain for Mexico.


It's been an awful 4 week period for that part of the country...and there's more to come most likely.
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Quoting xcool:
RedStickCasterette .WELCOME.


Thanks xcool. You seem like a polite person!

Not that we are always polite, lol.
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Quoting atmosweather:


Looking at visible imagery...a broad low pressure center may be trying to form around 22N 96.5W. It has definitely increased in organization since this morning but with the ULL about to move out to the N it will be drifting W-ward...I be surprised if anything developed.


Same here, I never considered it as a development threat, but geez, yet more rain for Mexico.
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Quoting HadesGodWyvern:


something to think about next week into the weekend..


Yes, we are coming to that stage...unfortunately!
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shear is.. different now rocketboy.. if you look over the SW caribean and the epac we dont have the screaming westerlies blanketing our entire basin. what we have now is a series of stubborn ULLs. They will shrink and move north as we head into the heart of the season and we begin to have the big highs take over.
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Quoting HadesGodWyvern:


something to think about next week into the weekend..


That tropical wave does bear watching.
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Quoting Levi32:
ASCAT pass from this morning (8 hours ago) showed turning of the winds from southeasterly to easterly, indicating a surface trough, and the 850mb vort max at that time was much broader and asymmetric. It has since tightened, strengthened, and become more circular, so the next ASCAT pass should reveal more organization at the surface as well.



Looking at visible imagery...a broad low pressure center may be trying to form around 22N 96.5W. It has definitely increased in organization since this morning but with the ULL about to move out to the N it will be drifting W-ward...I be surprised if anything developed.
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933. xcool
RedStickCasterette .WELCOME.
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.."Happy trails to you"..
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Quoting atmosweather:


Poof fool...he spent all last night providing great insight to those who asked for it and did it in a class manner.


Yes he did, and so did you.

That irks me...
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.