Tropical Weather Discussion...The poorly organized system that is Tropical Depression Bonnie continues to move swiftly to the WNW tonight. It is essentially just a mass of clouds with some scattered areas of storms as it moves through the Gulf. We are about 24 hours or so from landfall now.
Tropical Depression Bonnie Advisory
10p.m. CDT Friday, July 23, 2010
...Disorganized Bonnie remains a tropical depression...heading for the Northern Gulf...degeneration possible Saturday...
Latitude: 26.4 N
Longitude: 83.4 W
This places the exposed low-level center of Tropical Depression Bonnie about 395 miles ESE of the Mouth of the Mississippi River, and 85 miles SW of Sarasota, Florida.
Maximum Sustained Winds: 35 mph w/ higher gusts. Bonnie is poorly organized, but it could obtain minimal tropical storm status again on Saturday. Just a slight strengthening will bring Bonnie back up to tropical storm status, and that is currently reflected in the official forecast.
Movement: WNW or 295 degrees @ 17 mph. A general WNW motion and a reduction in forward speed is expected through the weekend. On this track, Bonnie will be approaching the Northern Gulf Coast by Saturday night into early Sunday.
Pressure: 29.83" or 1010 mb.
Watches/Warnings...The Tropical Storm Warning remains in effect for the Northern Gulf of Mexico Coast from Morgan City, LA to Destin, FL.
A Tropical Storm Warning means that Tropical Storm conditions are expected within the warning area generally in about 36 hours.
Rainfall...Bonnie will likely produce rainfall amounts of 1-3" across SE Louisiana, Southern Mississippi, Southern Alabama, and the Extreme Western Florida Panhandle. Isolated amounts up to 5" are possible in this area. An additional 1-2" of rain is expected across Central and Southern Florida through tonight.
Wind...Wind impacts will be minimal. Winds to tropical storm force mainly in squalls will gradually abate over South Florida, and conditions there will improve tonight. Conditions will begin deteriorating across the Northern Gulf Coast on Saturday with tropical squalls moving onshore by Saturday afternoon. Occasional tropical storm force winds will be possible in this area as the system moves onshore late Saturday night or early Sunday. The strongest winds will be confined to the immediate coastline.
Storm surge...Storm surge levels will rise by as much as 2-4' along and to the right of where the center makes landfall along the Northern Gulf Coast.
Discussion #6...Not really much change in forecast philosophy tonight. Bonnie remains one of the most poorly organized systems that I've ever seen. It remains a Tropical Depression, and it could ultimately degenerate on Saturday. A large ULL to the W of Bonnie is producing a high amount of shear across the Gulf, and this shear is tearing Bonnie apart with lots of dry air ingesting into the system. Bonnie is very elongated, and is not symmetrical at all. It is void of a lot of deep convection, and for most of its life the center of circulation has been displaced from the deep convection. This continues to the case tonight. The low-level center is on the SE flank of the storm, and the deepest convection right now is just off to the NW. The shear has increased this evening and tonight, and at present Bonnie is not much more than a mass of clouds with a few areas of tropical rain bands. The fast movement of Bonnie is also factoring into the equation with respect to its ability to strengthen. Bonnie has been a Tropical Depression since she emerged into the Gulf of Mexico Thursday evening. The official forecast still calls for Bonnie to return to minimal tropical storm status on Saturday before landfall, even though the Hurricane Center does mention the possibility that degeneration could occur.
The low-level center has moved almost due West for a time tonight, and some wobbles to the West are possible through Saturday, but generally a WNW heading is expected to continue as the flow around the large ULL and a high pressure to the North of Bonnie continue to steer it towards the Northern Gulf Coast. This motion will bring the storm to its landfall overnight Saturday or early Sunday. Bonnie continues to move rather swiftly between 15-20 mph, but the forward speed may decrease a hair through Saturday as the ULL tries to pull further away, and the high pressure to the North of the system may cause the pretty straightforward steering currents to lessen just a bit. The official forecast track has been nudged a bit to the left (West) mainly because of the denoted westward motion of the exposed low-level center. The official forecast still calls for Bonnie to make landfall to the East of the forecast area over SE Louisiana. The current official forecast projects a minimal tropical storm at landfall, but like I said a moment ago it may very well come ashore as just an open wave. Either way, moisture levels will begin to increase over the Bayou State on Saturday as the fringe effects of Bonnie begin to be felt. The outer rain bands of Bonnie will move onshore over SE Louisiana late Saturday, and spread Westward off and on through Tuesday. Rainfall will be the main threat over land, and only a minor increase in tide levels will be denoted along the coast. Wind will hardly be an issue at all, for remember, that most of our summertime thunderstorms are often stronger than a storm of this magnitude. SW Louisiana is certainly not out of the question as far receiving a direct hit from the disorganized tropical entity, but at this point of time the center of circulation looks to pass close to Baton Rouge. The remnant low will likely wind up in Northern Louisiana by Monday, and its position will likely open up the Gulf sending a continuous surge of tropical moisture over the area. Thus, rain chances should remain high through Tuesday.
That's all for this update. My next update will come Saturday morning after the 10a.m. advisory from the National Hurricane Center. The next intermediate advisory from the National Hurricane Center will be issued at 1a.m, followed by the next complete advisory at 4a.m. Saturday.
Have a great night & God bless!
-DM-
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