Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 7:55 PM GMT on October 05, 2005
The 5:16 pm EDT Hurricane Hunter mission found winds of 51 knots at flight level, supporting Tammy's maximum winds staying at 50 mph. The pressure fell 1 mb to 1002 mb, so Tammy is not strengthening rapidly, nor is she expected to. Tammy is maintaining her strength in the presence of some unusually high wind shear, about 20 - 25 knots. Tammy is poorly organized, and radar animations out of Jacksonville, Florida, show no sign of an eyewall forming, just a mass of disorganized echoes to the northeast of the center. No ships or buoys have actually measured tropical storm-force sustained winds of 40 mph yet. It is likely that Tammy will move onshore tonight as a weak tropical storm with maximum winds in the 50 - 55 mph range, and a storm surge of 2 - 4 feet.
The primary threat from Tammy will be from her rains. Bands of heavy rain continue to pound the coasts of northern Florida, Georgia, and the Carolinas. Rainfall amounts as of 4 pm EDT have mainly been in the 1 to 3 inch range along the coast in Georgia and along the South Carolina and northern Florida coasts, with lesser amounts further inland. A few isolated areas have received up to five inches--for example, Brunswick Georgia, and just south of Jacksonville, Florida. Storm total rainfall amounts of 3 to 5 inches are expected with isolated amounts of 8 to 10 inches along and to the north of Tammy's path. Flooding problems will be most serious in coastal Georgia, which received 3 - 5 inches of rain this past week, before Tammy came along.
Figure 2. Estimated rainfall from the Jacksonville radar.
Tammy is being drawn northward by an upper level low over the northern Gulf of Mexico. The counter-clockwise flow of air around this low will pull Tammy northwestward into Georgia, and perhaps even westward towards Alabama by Friday. A cold front is expected to arrive over the East Coast by Friday, and the remains of Tammy are expected to track up the front, drenching the entire East Coast.
A large area of thunderstorms broke off from Stan this morning, and emerged into the Yucatan Channel. Satellite imagery shows upper level outflow has developed to the north and east, along with some low-level spiral banding. There is a circulation center near the northeast tip of the Yucatan Peninsula, with a limited amount of deep convection to the northeast and east. Wind shear from westerly upper-level winds are pushing this convection away from the center. Observations from the Cancun radar indicate two major spiral bands have formed, one on the southeast side and one on the north side. The overall impression is of a weak sheared system that is not yet a tropical depression strength. Once the center moves further out into ocean, the system has a better chance for intensification. With wind shear of 10 knots over it, I believe this will be a tropical depression by tomorrow as the system tracks north-northeast towards western Florida. If this system were to be named, it would get the new name Vince, and not Stan, since the primary circulation of that storm pushed into the Pacific Ocean this morning. This assumes that the developing disturbance doesn't become a tropical storm first and steal the name Vince, leaving Stan Jr. stuck with the name Wilma.
Regardless of whether or not this system develops into a tropical storm, southwest Florida can expect tropical storm conditions, with rain amounts of 3 - 5 inches and high winds Thursday and Friday. The system will continue to the northeast and drench the areas already dumped on by Tropical Storm Tammy, and the entire East Coast needs to be concerned about serious flooding problems from this one-two punch.
Figure 1. BAMM model track for Stan Jr.--the tropical disturbance off of the Yucatan.
The death toll from Hurricane Stan now stands at 103, including 50 deaths in El Salvador, 34 in Guatemala, 11 in Nicaragua and eight in Mexico. The remnant circulation from Stan continues to pull moist tropical air from the Pacific Ocean into the disaster areas, where more flooding rains are expected to make the disaster even worse. Stan, who barely made it to Category 1 strength for a few hours, will likely have his name retired, thanks to this unfolding disaster. This would make the Hurricane Season of 2005 the first season to have five names retired (1955, 1995, and 2004 all had four storm names retired).
The remants of Stan appear likely to spin up into a new tropical cyclone that may threaten Baja California later in the week. If both this system and the Stan Jr. system off of the Yucatan do become tropical storms, this would be the first time a dissipated hurricane spawned two new tropical cyclones, one in the Atlantic and one in the Pacific. How many firsts can this season have??
A tropical disturbance near 9N 40W, 1500 miles east of the Lesser Antilles Islands, has developed a low level circulation, impressive deep convection, and the beginnings of an upper-level outflow channel to the north. About 10 knots of shear from strong westerly winds is affecting the disturbance, but models indicate that this shear may decrease over the next day or two. The disturbance is moving west at 15 - 20 mph. The early track forecasts are performing poorly--they have the disturbance moving to the northwest, and it is not doing so. However, a more norhtwestery motion is likely by Saturday, thanks to the steering influence of a large upper-level low pressure system at 25N 60W.
The disturbance is pretty far south for development to occur, but this hurricane season has had little regard for what is usual. Thus, the disturbance may form into a tropical depression on Thursday. Development is more likely Friday or Saturday, when the disturbance will be further from the equator and can take advantage of the Earth's spin to help it develop.
Figure 3. BAMM and GFDL model tracks for the mid-Atlantic disturbance.
Elsewhere in the tropics
Conditions are expected to be unusually conducive for tropical storm formation throughout the Atlantic for the next 10 days, and it is quite likely we'll make it to the end of the alphabet by mid-October. When that happens, we go Greek--Alpha, Beta, and hopefully not much further into the Greek Alphabet! One positive sign today that the Hurricane Season of 2005 will eventually end--a blizzard warning is up for western Montana.
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