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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Have a good night all.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
1230. JLPR2
Quoting xcool:
JLPR2 .348hr to far out


Well... its fun to look at I guess. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8691
1227. JLPR2
Quoting KoritheMan:


A Georges type track wouldn't be good for either of us, since Georges ultimately went from Puerto Rico to Louisiana/Mississippi (I'm in the former).


Yup, apparently that hurricane wanted to visit as many places as it could. LOL!
I'm impressed it reached you guys as a hurricane even after crossing so much land.
Member Since: September 4, 2007 Posts: 7 Comments: 8691
1226. xcool
JLPR2 .348hr to far out
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1224. JLPR2
Quoting xcool:
JLPR2.nw


hurray! LOL!
Member Since: September 4, 2007 Posts: 7 Comments: 8691
1223. xcool
KoritheMan iknow.
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1221. xcool
JLPR2.nw
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Quoting NCHurricane2009:


Interesting. I know we just had a disturbance in the region (98L) that made landfall. It was such a large, broad surface low, some of that low pressure field may still be over water. Not seeing the surface trough in this analysis:

http://www.nhc.noaa.gov/tafb/ATSA_18Z.gif

But then again, maybe its because they blocked it with the Bonnie label in the map, LOL.


I used this evening's ASCAT pass that shows a wind shift near the MX coast...appears to be a weak surface trough that has been left behind from 98L's remnants.
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Quoting xcool:


cv gfs

,ECMWF shows to.


This is 384 hours dude.
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Oh, ooooooooooooooh,

I took another look at the Bay of Campeche disturbance in this animation:

http://www.ssd.noaa.gov/goes/east/tatl/flash-ir4.html

I see a cyclonic rotation right along the east coast of Mexico, that I think is the surface trough you guys were mentioning. Okay, I see. Moreover, when you click on HDW-H (upper level winds), I see a small anticyclone has devloped over that area of rotation. Shear is reducing with this area also. Not making a prediction on this yet, need to keep seeing what's going on here.
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Quoting JLPR2:


yep, even the switch between the El Niño into La Niña was similar, I just hope the tracks are different. :S


A Georges type track wouldn't be good for either of us, since Georges ultimately went from Puerto Rico to Louisiana/Mississippi (I'm in the former).
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1214. JLPR2
Quoting xcool:


cv gfs

,ECMWF shows to.


its moving NW there right?
Please tell me NW! XD
Member Since: September 4, 2007 Posts: 7 Comments: 8691
1213. xcool


cv gfs

,ECMWF shows to.
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1211. JLPR2
SAL seems to be diminishing in areal coverage and in strength


Member Since: September 4, 2007 Posts: 7 Comments: 8691
1210. xcool
hello rob
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1209. JLPR2
Quoting KoritheMan:


Agreed. Based on what I've analyzed, this year's best analog is 1998.


yep, even the switch between the El Niño into La Niña was similar, I just hope the tracks are different. :S
Member Since: September 4, 2007 Posts: 7 Comments: 8691
Quoting ElConando:


So what you are saying is that there is a shot that the blob may interact with a tropical wave a couple days from now?


Yeah, its possible, not imminent. And it will be really important for the nearby ULL to the north to have weakened by the time the wave reaches the area, or shear will not let this develop.
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Quoting atmosweather:


The BOC disturbance has a decent near-surface reflection as there is a weak trough along that area of the Mexican coast. All the divergence that you mentioned is just helping fire the convection.


Interesting. I know we just had a disturbance in the region (98L) that made landfall. It was such a large, broad surface low, some of that low pressure field may still be over water. Not seeing the surface trough in this analysis:

http://www.nhc.noaa.gov/tafb/ATSA_18Z.gif

But then again, maybe its because they blocked it with the Bonnie label in the map, LOL.
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Quoting JLPR2:
Some food for thought:
1998 had
June: 0 storms
July: 1 storm
August: 4 storms
September: 6 storms
October: 2 storms
November: 1 storm

I'm thinking we could see something very similar with the exception that we could have an even busier October-November possibly September too thanks to the prime fuel we have.


Agreed. Based on what I've analyzed, this year's best analog is 1998.
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1204. will45
The placement of the ULL has been a prob so far. Sometimes the ULL is in a placement where it can actually help with the ventilation.
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Quoting NCHurricane2009:


The disturbance in the central Caribbean has no surface feature, its right now just T-storms produced by upper divergence between an anticyclone to the west and upper low to the north. Its the exact same setup as the area of interest in the Bay of Campeche tonight (also an area of upper divergence between anticyclone to the west and upper low to the north).

The central Caribbean disturbance looks stationary in this loop:

http://www.goes.noaa.gov/HURRLOOPS/huirloop.html

It will be interesting to see what happens when the tropical wave reaches the area in a couple of days. For now, just a blob


So what you are saying is that there is a shot that the blob may interact with a tropical wave a couple days from now?
Member Since: September 6, 2009 Posts: 2 Comments: 3720
1202. JLPR2
Some food for thought:
1998 had
June: 0 storms
July: 1 storm
August: 4 storms
September: 6 storms
October: 2 storms
November: 1 storm

I'm thinking we could see something very similar with the exception that we could have an even busier October-November possibly September too thanks to the prime fuel we have.
Member Since: September 4, 2007 Posts: 7 Comments: 8691
By the way, none of the new "blobs" are going to develop until the associated nearby upper lows weaken, reducing the shear.

This seems to have precluded development early this season, lots of ULLs creating pockets of shear wherever we get a disturbance. Alex was the only one this early season that got "lucky" (which gave bad luck to people who got affected by it of course).

Yeah, as those above are hinting, we gotta watch out as we generally expect a reduction in ULLs during ASO (August-September-and Early October).
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1190. KoritheMan 11:32 PM CDT on July 24, 2010

I think we'll see a return to a neutral MJO beginning in the second week of August, followed by an upward MJO shortly after that. No way it's going to be as dry as the GFS is forecasting, given the record warm SSTs this year.



Probably right, Kori, however, as we move into the heart of the season, imo, there'll be plenty of evaporation throughout the MDR to moisten the atmosphere. The MJO upward pulse, while helpful, won't need to be as much an influencing factor, again imo, as it does early and late in the season. Now, there'll probably be 10 posts that disagree with that and I look forward to those thoughts. ;P


Additionally, we'll probably see dust concentrations wane.
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Quoting NCHurricane2009:


The disturbance in the central Caribbean has no surface feature, its right now just T-storms produced by upper divergence between an anticyclone to the west and upper low to the north. Its the exact same setup as the area of interest in the Bay of Campeche tonight (also an area of upper divergence between anticyclone to the west and upper low to the north).

The central Caribbean disturbance looks stationary in this loop:

http://www.goes.noaa.gov/HURRLOOPS/huirloop.html

It will be interesting to see what happens when the tropical wave reaches the area in a couple of days. For now, just a blob


The BOC disturbance has a decent near-surface reflection as there is a weak trough along that area of the Mexican coast. All the divergence that you mentioned is just helping fire the convection.
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Quoting ElConando:


So it's likelihood of development is low then?


The disturbance in the central Caribbean has no surface feature, its right now just T-storms produced by upper divergence between an anticyclone to the west and upper low to the north. Its the exact same setup as the area of interest in the Bay of Campeche tonight (also an area of upper divergence between anticyclone to the west and upper low to the north).

The central Caribbean disturbance looks stationary in this loop:

http://www.goes.noaa.gov/HURRLOOPS/huirloop.html

It will be interesting to see what happens when the tropical wave reaches the area in a couple of days. For now, just a blob
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Quoting will45:
we had this same lull in 2005 around this time. And we all know how the rest of that season turned out.


Right. Not to mention that both Harvey and Irene, a long track Cape Verde hurricane, developed during this period, as did Tropical Depression Ten, which ultimately helped to develop the notorious Hurricane Katrina.

We can still get tropical cyclones while we're in the downward MJO pulse. It's just harder.
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Quoting KoritheMan:


Atlantic appears rather dry at the moment, and though I feel that the GFS is being far too aggressive with its forecast of an unusually strong downward MJO motion pulse, the forecast of a downward MJO persisting into at least the first week of August cannot be so easily ignored.

I think we'll see a return to a neutral MJO beginning in the second week of August, followed by an upward MJO shortly after that. No way it's going to be as dry as the GFS is forecasting, given the record warm SSTs this year:



I agree...the global models have consistently been forecasting a downward MJO phase for the Atlantic Basin for 2-3 weeks and yet there is just way too much heat in the Basin for any significant and long-lived downward phase to occur:

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Quoting NCHurricane2009:


Yep, that's where the center of my cone pointed Bonnie this morning. Glad this system wasn't so bad near the oil spill and for folks in Louisiana who really really don't deserve a storm right now.


I'm glad as well. Though it's still early, and if the steering we've seen thus far is any indication, the Gulf is in for a rough ride this year, similar to 1998 and 2008.
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1194. will45
we had this same lull in 2005 around this time. And we all know how the rest of that season turned out.
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1193. xcool
<<<< 6 named storms for August


When will next storm form july 27 to August 3.imo
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Quoting tennisgirl08:
Storm or Levi - could either of you explain why there is so much dry air and ULLs in the tropical atlantic right now? Is this normal for early in the season, and will there be less of it in Aug-Oct when we expect the season to ramp up? Just curious - b/c regardless of warm SSTs if the upper environmental conditions are not favorable nothing can really develop - i.e. Bonnie. Thanks in advance.


I think both Storm and Levi are away but I'll answer it...basically ULL's are very common throughout hurricane season but it's the placement and frequency that make the difference. Typically in June and July, we see more ULL's develop at the base of the TUTT that resides further S into the SW Atlantic during this period, allowing these upper systems to disrupt more tropical cyclones because they are further S near the main development region. Once August comes, the TUTT climatologically moves N-ward (and this has already begun) and so any ULL's that come across the Atlantic are further N and will have less of a negative impact. The dry air in the Atlantic is mainly due to a combination higher than normal heights caused by the strength of the Azores/Bermuda ridge producing fair weather, and the Saharan dust layer that traverses the basin during the early part of the season, but this dry air will start to fade a little during the next couple of weeks thanks to a retreating and weakening subtropical ridge and the above normal rainfall that has been falling across the desert regions of Africa, preventing a lot of dust from making it into the Basin.
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Quoting atmosweather:


The low level steering is rather weak but the disturbance is moving to the W around 5-10 mph, and should continue to do so for the next day or so as it approaches central America.


So it's likelihood of development is low then?
Member Since: September 6, 2009 Posts: 2 Comments: 3720
Quoting will45:
CMC hardly sees anythig out there so you know it is quiet.


Atlantic appears rather dry at the moment, and though I feel that the GFS is being far too aggressive with its forecast of an unusually strong downward MJO motion pulse, the forecast of a downward MJO persisting into at least the first week of August cannot be so easily ignored.

I think we'll see a return to a neutral MJO beginning in the second week of August, followed by an upward MJO shortly after that. No way it's going to be as dry as the GFS is forecasting, given the record warm SSTs this year:

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Quoting KoritheMan:
Bonnie making "landfall" in extreme lower Plaquemines Parish, Louisiana, near 29N 89W:



Notice the faint but distinct swirl in that location, just south of Buras.


Yep, that's where the center of my cone pointed Bonnie this morning. Glad this system wasn't so bad near the oil spill and for folks in Louisiana who really really don't deserve a storm right now.
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Evening folks,

I finally nailed a forecast with Bonnie, woohoo! My 8 AM EDT track and intensity forecast was accurate. I really like how my track forecast was to the left of the NHC's, which is verifying spot on tonight!
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Bonnie making "landfall" in extreme lower Plaquemines Parish, Louisiana, near 29N 89W:



Notice the faint but distinct swirl in that location, just south of Buras.
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1186. xcool
hmm sw cab
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1185. will45
CMC hardly sees anythig out there so you know it is quiet.
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Well good night everyone.Have a safe and blessed night.Again thank you Xcool for the great information.I will be watching closely.
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Quoting Orcasystems:
Pick a Blob... dime a dozen :)


AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI


Be interesting to see if we have a winner come later this coming week.

May get a couple more "stat padders" before the meat of the season begins.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
Quoting ElConando:
1165. What direction will the SW Caribbean disturbance move.


The low level steering is rather weak but the disturbance is moving to the W around 5-10 mph, and should continue to do so for the next day or so as it approaches central America.
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Pick a Blob... dime a dozen :)


AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
Member Since: Posts: Comments:

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About

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