Tropical Weather Discussion...Tropical Depression 3 forms near the Bahamas. This is the former Invest 97L which we've been tracking all week. The system is still showing signs of becoming better organized, and a Hurricane Hunter Aircraft will be in the system later today to investigate, and determine if TD 3 has become Tropical Storm Bonnie. A Gulf Coast threat appears imminent with the future Bonnie. All the specifics, and my first discussion on TD 3 follow.
Tropical Depression 3 Advisory
...The seasons third tropical system forms near the Bahamas...National Hurricane Center issues advisories and watches and warnings as of 10a.m.
10a.m. CDT Thursday, July 22, 2010
Latitude: 21.9 N
Longitude: 75.0 W
This position is 265 miles SE of Nassau, Bahamas and 405 miles ESE of Key Largo, Florida.
Maximum sustained winds: 35 mph w/ higher gusts. Satellite imagery suggests that TD 3 is becoming more organized despite some shear on the western flank of the storm. An Air Force Hurricane Hunter Aircraft is en route, and will be investigating the system this afternoon to see if any strengthening has occurred. Slow strengthening is forecast over the next 24 hours. It won't take much strengthening at this point for an upgrade to Tropical Storm Bonnie to occur, and this system will likely become Tropical Storm Bonnie later today.
Movement: WNW or 295 degrees @ 15 mph. This motion is expected to continue over the next couple of days, and an increase in forward speed is expected by the weekend. On this track, TD 3 and eventually Bonnie will be moving through the Florida Keys and Florida Straits on Friday, and then into the SE Gulf of Mexico late Friday.
Pressure: 29.77" or 1005 mb.
Watches/Warnings...The government of the Bahamas has issued a Tropical Storm Warning for the Central and Northwestern Bahamas. A Tropical Storm Warning is also in effect for the East Coast of Florida from Golden Beach southward including all of the Florida Keys and Florida Bay, and for the West Coast of Florida to Bonita Beach.
A Tropical Storm Watch has been issued to the North of the Tropical Storm Warning area on the East Coast of Florida from Golden Beach to Jupiter Inlet including Lake Okeechobee.
A Tropical Storm Warning means that Tropical Storm conditions are expected within the warning area generally in about 36 hours. A Tropical Storm Watch means that Tropical Storm conditions are possible within the watch area generally within 48 hours.
Rainfall...Rainfall totals of 2-4" are expected to occur over South Florida, with higher amounts of 4-6" possible in some locations. Rainfall totals of 3-5" are expected over the Bahamas, with higher totals up to near 7" expected in isolated locales.
Wind...Winds around Tropical Storm force are already occurring over portions of the SE Bahamas. Tropical Storm conditions will spread over the Central and Northwestern Bahamas tonight and Friday, and into South Florida later on Friday.
Storm surge...Storm surge levels will rise 1-2' above ground level over South Florida, the Florida Keys and the Bahamas.
Discussion...TD 3 has been trying and trying all week to get organized, and has spent much of the week as an area of investigation, hence the former Invest 97L. There has been a decent amount of shear off to the NW of the system in response to a large ULL over the Western Atlantic. This ULL has moved far enough away this morning to allow a more favorable environment for development over the Western Atlantic. The storm is organizing in the general vicinity of the Bahamas. It is still poorly organized with the low-level center on the SW flank of the storm just removed from the deep convection to the E and NE. It is possible that this system has already obtained tropical storm status, and a Hurricane Hunter Plane is en route to investigate.
The environment in this region will gradually become more favorable, but the most ideal conditions for development may never take affect depending on the motion of the ULL in the vicinity of the storm. A steady forward motion, and interaction with land will also inhibit development. That being said, it won't take much strengthening to upgrade TD 3 to Tropical Storm Bonnie. I fully expect this system to become Bonnie this afternoon as it continues to move to the WNW around the periphery of the Bermuda high to the North of the system. The center of the system is forecast to miss mainland Florida, and shoot through the Keys and Florida Straits before entering the Gulf in about 36 hours. However, since the system is still organizing some adjustments to the low-level center are possible.
The future of TD 3 is still a bit uncertain due to the continued organization of the system. However, model consensus suggests a threat to SW Louisiana. Many of the most reliable models have landfall clustered over our general area. The good news is given the marginally conducive environment that TD 3 will have to work with and the steady forward progress, rapid strengthening is not anticipated. If the environmental set up over and out ahead of the storm improve then a stronger storm is certainly possible. SSTs over the Gulf support development. The motion to the WNW should continue through at least Sunday as the ridge over the SE U.S. intensifies. Towards the end of its journey late Sunday into Monday, a turn toward the NW or North is expected as the system rounds the Western periphery of the trough. This will bring the storm very close to SW Louisiana late Sunday or early Monday. The current intensity forecast calls for a 50 mph tropical storm at landfall. The official track shows landfall in Cameron Parish in the aforementioned Sunday night/early Monday period, from there it tracks right over or very near Lake Charles Monday morning, and then parallels the Sabine River Valley moving up into East Texas through Tuesday. This would place all of SW Louisiana on the bad side of the system. Granted, this is not forecast to be a hurricane, but it will still produce some adverse weather especially along the coast. An increase in tides and a storm surge of 3-4' is possible along the Cameron and Vermilion Parish coastline, with a rise in water levels along the Calcasieu River from Lake Charles southward. Further revisions to the forecast will be forthcoming as necessary depending on adjustments to intensity and the forecast track. On the current track, winds in the coastal parishes could be in the 50-60 mph range while they will be incremently less further inland. If the current track holds to fruition, then the Lake Charles area would see winds in the 40-50 mph range Sunday night and Monday. Heavy rainfall will envelop the entire area as the system moves towards the coast. Rainfall will begin as early as Saturday afternoon or evening over the SE portion of the forecast area, and then overspread the entire area by Sunday afternoon as the system makes its move for the coast. The threat for flooding and isolated tornadoes will also likely be realized. Rainfall amounts of 5-10" for Sunday and Monday are expected across the forecast area as the storm's impact is felt.
The official forecast track laid out by the NHC seems logical at this point, and I see no reason to suggest a different track. I believe in the end this system will wind up on a track similar to Rita in 2005, but IT WILL NOT mirror Rita in intensity by any means. I do believe the official intensity forecast could be a little low, but I still believe this will be a tropical storm at landfall. I believe winds in the 60-65 mph range at landfall are conceivable. The agreement between the models with a developing storm is quite good, and based on the current synoptic features that will steer this system, a landfall in Louisiana seems logical at this point. Of course, a deviation of course further to the left or the right is possible considering the fact that this storm is still in an organizing mode, therefore, everyone from the Upper Texas coast to the Florida Panhandle needs to keep abreast of the latest forecast. Right now though, we seem to be in the crosshairs of the most adverse weather associated with what will become Bonnie, and I would expect the National Hurricane Center is to issue Tropical Storm Watches for our area sometime on Friday, with warnings to follow on Saturday. Additional advisories from the National Weather Service in Lake Charles will likely be forthcoming as well as the storm gets closer. Graphics follow:
Invest 98L is still trying to get better organized in the Southern Gulf, but this is of no concern to us. The next update on TD 3 will be around mid-afternoon once the data from the Recon plane becomes available, and the National Hurricane Center posts a new advisory. Also, a regular blog illustrating exactly what type of weather we can expect will be posted tonight. Stay tuned!
Have a great Thursday and God bless!
-DM-
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