Bonnie weakens to a tropical depression

By: Dr. Jeff Masters , 8:40 PM GMT on July 23, 2010

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Tropical Depression Bonnie is nearing the end of its traverse of South Florida, and passage over land has significantly disrupted the small storm. Satellite images show almost no heavy thunderstorms near Bonnie's center of circulation, and the center is now exposed to view. Radar-estimated rainfall from the Key West radar shows that Bonnie dumped very little rain on South Florida--maximum rainfall amounts from the storm were about four inches over a small region southwest of Miami. Water vapor satellite loops show that Bonnie is embedded in a large area of dry air, thanks to an upper level low to the west over the Gulf of Mexico. This low has brought an increasing amount of wind shear to Bonnie today, and shear has increased from 20 knots this morning to 25 knots this afternoon. Surface observations in South Florida currently don't show any tropical storm force winds. Bonnie's top winds today were at Fowey Rocks, which had sustained winds of 46 mph, gusting to 53 mph, at 10:45 am EDT.


Figure 1. Satellite image of Bonnie from NASA's MODIS instrument, taken at 17:10 UTC July 23, 2010. Image credit: NASA/.

Track Forecast for Bonnie
The latest set of model runs from 8am EDT (12Z) are very similar to the three previous sets of runs, and this degree of consistency gives me confidence that Bonnie will stay within the cone of uncertainty depicted on the track forecast images. The projected track will take Bonnie over the oil spill region, and the storm's strong east to southeasterly winds will begin to affect the oil slick on Saturday morning. Assuming Bonnie doesn't dissipate over the next day, the storm's winds, coupled with a likely storm surge of 2 - 4 feet, will drive oil into a substantial area of the Louisiana marshlands. However, the current NHC forecast has Bonnie 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. The latest oil trajectory forecasts from NOAA (Figure 2) predicts potential oil impacts along a 150-mile stretch of Louisiana coast on Sunday.


Figure 2. Oil Trajectory forecast for Sunday for the Deepwater Horizon oil spill. Image credit: NOAA.

Intensity Forecast for Bonnie
Bonnie has been disrupted by its passage over land, and it will take at least six hours for the storm to reorganize once it moves over the warm waters of the Gulf of Mexico tonight. This process will be hindered by the large upper-level low to its west. If the low remains in its present location, relative to Bonnie, it will bring high wind shear of about 20 - 30 knots to the storm. This will allow for only slow intensification, or may even destroy Bonnie. Bonnie is unlikely to intensify to more than a 50 mph tropical storm, and I give a 30% chance it will dissipate over the Gulf of Mexico before making landfall. The GFDL model predicts Bonnie could hit the Gulf Coast as a 50 mph tropical storm, but the other major models such as the HWRF, GFS, ECMWF, and NOGAPS show a much weaker storm. I don't give Bonnie any chance of becoming a hurricane. NHC is putting the odds of Bonnie being a hurricane at 2 pm Saturday at 4% (5pm advisory.)

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 probabilities of various locations getting tropical storm force winds, 39 mph or higher, from the 5pm EDT advisory:

Buras, LA 30%
New Orleans 28%
Mobile, AL 37%
Pensacola, FL 30%

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 Saturday morning.

Jeff Masters

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1561. Levi32
Quoting GBguy88:


If I could, I would trade you a hurricane and 3 months of 90 heat for a breath of Alaskan air :-) You're fortunate to live in such a beautiful state. That said, there's nothing quite like being inside the eye of a hurricane, especially a strong one ;-) Definitely straying off topic now, but what's the coldest temperature you've ever felt? For me it's single digit wind chills, but never subzero. I'm fascinated by bitter cold for some reason.


Oh we're not off topic it's the weather....and it's not like there's a hurricane about to come ashore.

Coldest I've seen was -28F here in Homer, which is really quite moderate because I've grown up in a warm PDO period. Frankly, we could be about to see the worst winter here in Alaska in over 30 years this winter, with the PDO going as cold as it is right now. It's going to be dang brutal, and with my college up in Fairbanks, I'll be guaranteed to see -50F and below on several nights. The next couple decades will restore our reputation as the most dangerous place to live in North America, similar to the weather Alaska was known for from the late 1940s through the mid-1970s when the PDO was last cold.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting scott39:
Good thats what I want to hear? What about the window for small strengthing before landfall?


Very slight chance if the storm doesn't degenerate into a remnant wave overnight tonight.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting angiest:


Humberto hit High Island, correct? So west Houston could have been bone dry and sunny and hot.


Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting atmosweather:


It was haunting...luckily Andrew was moving quickly and was a small storm...we only had hurricane force winds for around 4 hours. But that was more than enough...way more.



wilma was scary too
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Quoting atmosweather:


Yep...originally listed as 145 mph but later revised to 165 mph...and even that is conservative IMO. Many stations around our area (just S of Miami) recorded sustained winds over 140 kts before instrument failure.


I've heard the same reports too..and I think I remeber straw in chopped down telephone poles.

Miami was like Tampa with charley...a very close call. Could of been a lot worse than it already was...
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1556. scott39
Quoting atmosweather:


It means that any convection that fires up no matter how impressive may look cannot be sustained for long because of the strong upper flow and the fact that the system is still decoupled and has an awfully defined LLC.
Good thats what I want to hear? What about the window for small strengthing before landfall?
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Quoting chrisdscane:



how much were ur ears hurting all that night omg


It was haunting...luckily Andrew was moving quickly and was a small storm...we only had hurricane force winds for around 4 hours. But that was more than enough...way more.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting atmosweather:


Yep...originally listed as 145 mph but later revised to 165 mph...and even that is conservative IMO. Many stations around our area (just S of Miami) recorded sustained winds over 140 kts before instrument failure.



then my doors blew out we were all in the bathroom under the sink
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1553. xcool
Bonnie PLAYER HEAD GAMES....
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Quoting atmosweather:


It means that any convection that fires up no matter how impressive may look cannot be sustained for long because of the strong upper flow and the fact that the system is still decoupled and has an awfully defined LLC.


so dont get to excited however i still beleive itll regain storm status
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1551. xcool
you never try BACK ON STORMS .
Member Since: September 26, 2009 Posts: 2 Comments: 15670
1550. angiest
Quoting TexasHurricane:


really.....yeah, we got rain. My son wanted to play in it all day after the storm passed. We got to use the generator and all. Power was only out for the day. Got is back that night.


Humberto hit High Island, correct? So west Houston could have been bone dry and sunny and hot.
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Quoting cntrclckwiseSpenn:


That wasn't even listed as a Cat 5 at the time. I think they later upgraded it to a Cat 5 status after it was long gone.


Yep...originally listed as 145 mph but later revised to 165 mph...and even that is conservative IMO. Many stations around our area (just S of Miami) recorded sustained winds over 140 kts before instrument failure.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1547. angiest
Quoting cntrclckwiseSpenn:


That wasn't even listed as a Cat 5 at the time. I think they later upgraded it to a Cat 5 status after it was long gone.


A decade or more I believe.
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Quoting angiest:


For some bizarre reason I don't remember Humberto at all. Must not have given us any rain even.


really.....yeah, we got rain. My son wanted to play in it all day after the storm passed. We got to use the generator and all. Power was only out for the day. Got is back that night.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting scott39:
So this means nothing for developement?


It means that any convection that fires up no matter how impressive may look cannot be sustained for long because of the strong upper flow and the fact that the system is still decoupled and has an awfully defined LLC.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting atmosweather:


It's indescribable in both extremes. The meteorological side in you is in awe...the human side of you is literally scared to death. Although out of the 6 hurricanes I've been through...Andrew's the only one I never want a repeat of.


That wasn't even listed as a Cat 5 at the time. I think they later upgraded it to a Cat 5 status after it was long gone.
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1543. GBguy88
Quoting Levi32:


Haha I want to....something not freakily dangerous like a Cat 1 would even suffice.

I have never even really been out of Alaska except for one trip to rural Ohio in the winter which looks no different lol, so no I have not experienced tropical weather of any kind....haven't even felt what 80-degree weather feels like.

But, I have been through the equivalent of a Cat 1-2 hurricane when we had a 931mb winter storm come up the Aleutian Islands, and while it was weakening as it moved into our area, we still got 80-90mph winds with gusts up to 110 for 8-12 hours, which ripped over half the shingles off our roof and downed more trees than any storm since. I was around 6 or 7 at the time. 1998 if I'm not mistaken.


If I could, I would trade you a hurricane and 3 months of 90+ heat for a breath of Alaskan air :-) You're fortunate to live in such a beautiful state. That said, there's nothing quite like being inside the eye of a hurricane, especially a strong one ;-) Definitely straying off topic now, but what's the coldest temperature you've ever felt? For me it's single digit wind chills, but never subzero. I'm fascinated by bitter cold for some reason.
Member Since: Posts: Comments:
Quoting atmosweather:


It's indescribable in both extremes. The meteorological side in you is in awe...the human side of you is literally scared to death. Although out of the 6 hurricanes I've been through...Andrew's the only one I never want a repeat of.



how much were ur ears hurting all that night omg
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Quoting Levi32:


Goodness how much higher can the pressure get.


The only thing that's really keeping the winds in the 30-35 kt range is honestly the gradient between the strong ridge to the north and this area of "low" pressure. 1013mb is extraordinary...almost like Andrew early in it's life (1015mb).
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1540. xcool
move WNW & HOT SST ANYWAY..
Member Since: September 26, 2009 Posts: 2 Comments: 15670
1539. angiest
Quoting TexasHurricane:


well I have to say Humberto (cat 1) was pretty cool. Thought we were going to have a tropical storm and woke up to a Hurricane. Needless to say I couldn't go back to sleep. I had to look out the windows...... :)


For some bizarre reason I don't remember Humberto at all. Must not have given us any rain even.
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1538. scott39
Quoting atmosweather:
RECON fix shows that the LLC has continued to be dragged almost W-ward by the strong low level flow...the convection that has fired up is all NW of the center and being pulled away from the LLC by the SE-erly upper flow.
So this means nothing for developement?
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1537. JLPR2
O.o? 36Kt?
Bonnie is one deceiving system
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1536. angiest
Quoting jlp09550:


The little engine that could..


This could conceivable beat Marco.
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Quoting cntrclckwiseSpenn:


I have not been through a hurricane either, and I'm on the coast of FL. Not sure I want to after hearing stories from Hurricane Andrew and Charley.


It's indescribable in both extremes. The meteorological side in you is in awe...the human side of you is literally scared to death. Although out of the 6 hurricanes I've been through...Andrew's the only one I never want a repeat of.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Levi32:


Haha I want to....something not freakily dangerous like a Cat 1 would even suffice.

I have never even really been out of Alaska except for one trip to rural Ohio in the winter which looks no different lol, so no I have not experienced tropical weather of any kind....haven't even felt what 80-degree weather feels like.

But, I have been through the equivalent of a Cat 1-2 hurricane when we had a 931mb winter storm come up the Aleutian Islands, and while it was weakening as it moved into our area, we still got 80-90mph winds with gusts up to 110 for 8-12 hours, which ripped over half the shingles off our roof and downed more trees than any storm since. I was around 6 or 7 at the time. 1998 if I'm not mistaken.


well I have to say Humberto (cat 1) was pretty cool. Thought we were going to have a tropical storm and woke up to a Hurricane. Needless to say I couldn't go back to sleep. I had to look out the windows...... :)
Member Since: July 2, 2009 Posts: 0 Comments: 2811
1533. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15670


The little engine that could..
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1531. Levi32
Quoting atmosweather:
000
URNT12 KNHC 240508
VORTEX DATA MESSAGE AL032010
A. 24/05:00:30Z
B. 26 deg 27 min N
084 deg 11 min W
C. 925 mb 797 m
D. 36 kt
E. 052 deg 28 nm
F. 129 deg 37 kt
G. 052 deg 34 nm
H. EXTRAP 1013 mb
I. 22 C / 758 m
J. 23 C / 760 m
K. 22 C / NA
L. NA
M. NA
N. 1345 / 9
O. 0.02 / 3 nm
P. AF305 0603A BONNIE OB 15
MAX FL WIND 44 KT N QUAD 01:46:40Z
SLP EXTRAP FROM 925 MB
MAX FL TEMP 24 C 060 / 9 NM FROM FL CNTR


Goodness how much higher can the pressure get.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
RECON fix shows that the LLC has continued to be dragged almost W-ward by the strong low level flow...the convection that has fired up is all NW of the center and being pulled away from the LLC by the SE-erly upper flow.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1529. xcool
wow she get better
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Quoting Levi32:


Haha I want to....something not freakily dangerous like a Cat 1 would even suffice.

I have never even really been out of Alaska except for one trip to rural Ohio in the winter which looks no different lol, so no I have not experienced tropical weather of any kind....haven't even felt what 80-degree weather feels like.

But, I have been through the equivalent of a Cat 1-2 hurricane when we had a 931mb winter storm come up the Aleutian Islands, and while it was weakening as it moved into our area, we still got 80-90mph winds with gusts up to 110 for 8-12 hours, which ripped over half the shingles off our roof and downed more trees than any storm since. I was around 6 or 7 at the time. 1998 if I'm not mistaken.


I have not been through a hurricane either, and I'm on the coast of FL. Not sure I want to after hearing stories from Hurricane Andrew and Charley.
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1527. xcool
36k now hmmm
Member Since: September 26, 2009 Posts: 2 Comments: 15670
1526. angiest
Looks like the vortex supports upgrade to TS.
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000
URNT12 KNHC 240508
VORTEX DATA MESSAGE AL032010
A. 24/05:00:30Z
B. 26 deg 27 min N
084 deg 11 min W
C. 925 mb 797 m
D. 36 kt
E. 052 deg 28 nm
F. 129 deg 37 kt
G. 052 deg 34 nm
H. EXTRAP 1013 mb
I. 22 C / 758 m
J. 23 C / 760 m
K. 22 C / NA
L. NA
M. NA
N. 1345 / 9
O. 0.02 / 3 nm
P. AF305 0603A BONNIE OB 15
MAX FL WIND 44 KT N QUAD 01:46:40Z
SLP EXTRAP FROM 925 MB
MAX FL TEMP 24 C 060 / 9 NM FROM FL CNTR
Member Since: September 24, 2005 Posts: 33 Comments: 9265
1524. xcool
lol
Member Since: September 26, 2009 Posts: 2 Comments: 15670
1523. angiest
Quoting cirrocumulus:
angiest: no, it's just higher temp waters on the west side. However, the east side is now enering warmer waters also.


I did say that was a joke. The location of the "pinhole eye" is not even near the COC.

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1522. xcool
jlp09550 hey i try alotttttttt woof call all dog lol
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Last update... Night all... have fun



AOI

AOI

AOI

AOI

Landfall Points

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting xcool:
dirty old lady not dead




Haha, nice one.
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Quoting chrisdscane:


dude i went through wilmaa no lie i almost died ill tell story if u wanan hear?


ill say it anyway typing it now
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angiest: no, it's just higher temp waters on the west side. However, the east side is now enering warmer waters also.
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1517. Levi32
Quoting GBguy88:


Just out of curiosity, not to stray from topic of current tropics...but have you ever been through a hurricane? For someone with such a passion for the tropics, you should try it sometime if you haven't :)


Haha I want to....something not freakily dangerous like a Cat 1 would even suffice.

I have never even really been out of Alaska except for one trip to rural Ohio in the winter which looks no different lol, so no I have not experienced tropical weather of any kind....haven't even felt what 80-degree weather feels like.

But, I have been through the equivalent of a Cat 1-2 hurricane when we had a 931mb winter storm come up the Aleutian Islands, and while it was weakening as it moved into our area, we still got 80-90mph winds with gusts up to 110 for 8-12 hours, which ripped over half the shingles off our roof and downed more trees than any storm since. I was around 6 or 7 at the time. 1998 if I'm not mistaken.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting Levi32:


The disturbance near Hispaniola is mid-level with little surface reflection right now, and isn't an immediate threat but should be watched....it's a sneaky little devil.

A little more moisture supply may help Bonnie generate some convection up until landfall, but that can be expected with any tropical system, and I doubt any real strengthening will take place. It's already on the edge of opening fully up back into an open wave, and it would be hard to get this back up to a tropical storm. The new burst of convection is interesting though and should be monitored. You never know what these things can do in the gulf.
Thanks for the quick response.
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Quoting GBguy88:


I think Pensacola would have been the oldest settlement in the country, but was destroyed (or severely disrupted) by a hurricane early in the 1500s. I think it's St. Augustine with the title now. Could be wrong.


Jacksonville next???
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1513. xcool
dirty old lady not dead


Member Since: September 26, 2009 Posts: 2 Comments: 15670
1512. Levi32
Quoting LightningCharmer:
A near Earth asteroid (1999 JD6) will pass within 50 lunar distances on July 27. Its estimated size is roughly 2 kilometers in diameter.

NASA Jet Propulsion Laboratory

SpaceWeather.com

How close should we be watching the cloudiness and slight turning just north of Hispaniola, or is it mostly mid and upper level? The cloudiness has maintained over the last several frames.

It also appears the dry air from the Upper Level Low in the western Gulf of Mexico is being cutoff by moisture from the south. Should one expect strengthening from Bonnie?


The disturbance near Hispaniola is mid-level with little surface reflection right now, and isn't an immediate threat but should be watched....it's a sneaky little devil.

A little more moisture supply may help Bonnie generate some convection up until landfall, but that can be expected with any tropical system, and I doubt any real strengthening will take place. It's already on the edge of opening fully up back into an open wave, and it would be hard to get this back up to a tropical storm. The new burst of convection is interesting though and should be monitored. You never know what these things can do in the gulf.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting GBguy88:


Just out of curiosity, not to stray from topic of current tropics...but have you ever been through a hurricane? For someone with such a passion for the tropics, you should try it sometime if you haven't :)


dude i went through wilmaa no lie i almost died ill tell story if u wanan hear?
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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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