Bonnie makes landfall in South Florida

Tropical Storm Bonnie is making landfall in South Florida south of Miami as a minimal tropical storm with 40 mph winds. Radar-estimated rainfall from the Miami radar shows that Bonnie is a relatively dry storm--maximum rainfall amounts from the storm have been just 2 - 3 inches over the waters to the east 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. Over the past twelve hours, Bonnie has sped up, and this has brought the storm closer to the upper level low. The upper level low is now bringing high levels of wind shear--about 20 knots--to the tropical storm. Satellite images of Bonnie show that the storm is being stretched into an oval shape by the strong steering flow, and this distortion is inhibiting intensification. Bonnie is a small storm, and is only affecting a limited area of South Florida with strong winds and heavy rain. Surface observations in the Bahamas and South Florida showed a number of stations with winds in the 30 - 46 mph range this morning, including Fowey Rocks, which had sustatined winds of 46 mph, gusting to 53 mph, at 10:45 am EDT.


Figure 1. Radar image of Bonnie at landfall from the Miami radar.

Track Forecast for Bonnie
Bonnie has sped up more than the models expected, but they are in pretty good agreement about a continued track to the west-northwest to northwest with a landfall between Louisiana and the Florida Panhandle. The latest set of model runs from 2am EDT (6Z) are very similar to the two 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. These winds, coupled with a storm surge of 2 - 4 feet, will result in a substantial area of the Louisiana marshlands getting oiled. The latest oil trajectory forecasts from NOAA (Figure 2) predict potential oil impacts along a 150-mile stretch of Louisiana coast on Sunday. Given Bonnie's rapid forward speed, small size, and expected landfall intensity of 50 mph or less, oil impacts on the Louisiana coast will be similar to or less than what was experienced 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.


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

Intensity Forecast for Bonnie
The primary detriment to development of Bonnie will be the presence of 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 knots to the storm. This will allow for only slow intensification, and Bonnie is unlikely to intensify to more than a 50 mph tropical storm. This is the solution of the major global models such as the GFDL, HWRF, GFS, ECMWF, and NOGAPS. However, if the upper-level low weakens or pulls away from Bonnie, less shear and dry air will affect the storm, potentially allowing Bonnie to intensify to a strong tropical storm with 60 - 65 mph winds. The more statistically based intensity models--SHIPS and LGEM--foresee this sort of scenario. I'll go with the lower intensity scenario, since Bonnie is such a small storm and will be more sensitive than usual to hostile wind shear and dry air. I give Bonnie a 10% chance of becoming a hurricane. NHC is putting the odds of Bonnie being a hurricane at 8 pm Saturday at 9% (11am 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 11am EDT advisory :

Buras, LA 41%
New Orleans 32%
Mobile, AL 37%
Pensacola, FL 31%

Moscow records its hottest temperature in history
The temperature in Moscow, Russia reached 37°C (98.6°F) today, the hottest temperature ever recorded in the city. According to Wikipedia, Moscow's previous highest temperature ever recorded was 36.8°C (98.2°F) in August 1920. With the wunderground.com forecast for Moscow calling for continued temperatures in the mid to upper nineties for the next week, Moscow should easily be able break its record for warmest July since record keeping began in 1879.

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 this afternoon.

Jeff Masters