
Convection needs to increase before any upgrade can occur
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RL3AO wrote:Upgrade to what? Theres no one to upgrade it. HPC is calling it a subtropical cyclone. Thats probably about as much as we will get unless I'm missing something.
Macrocane wrote:RL3AO wrote:Upgrade to what? Theres no one to upgrade it. HPC is calling it a subtropical cyclone. Thats probably about as much as we will get unless I'm missing something.
Upgrade to tropical, if convection increses near the center it could be upgraded to a tropical cyclone.
Posted by: JeffMasters, 2:10 PM GMT on March 10, 2010
A rare weather event is underway in the South Atlantic Ocean, where the basin's 7th recorded tropical or subtropical cyclone of all-time has formed. An area of disturbed weather (Invest 90Q) off the coast of Brazil, near 30S 48W, attained a well-defined surface circulation, top wind speeds of tropical depression strength (35 mph), a warm core in the bottom portion of the atmosphere, and a cold core aloft last night. If this storm had been in the North Atlantic, there is a good chance it would have been named Subtropical Depression One. However, tropical and subtropical storms are so rare in the South Atlantic that there is no official naming of depressions or storms done. The cyclone had top winds of at least 35 mph as seen on an ASCAT pass at 7:45 pm EST last night (Figure 2), and satellite estimates of the storm's intensity topped out at 40 mph (minimum subtropical storms strength) last night. This morning, the satellite estimates are showing that the system has weakened to a 35 mph tropical depression. There is some moderate wind shear interfering with development, and sea surface temperatures are about 25°C, which is about 1°C below what is typically needed to support a tropical storm. The storm is headed eastward out to sea, and is not a threat to any land areas. The models show the storm will lose its tropical characteristics and get absorbed by a frontal system by Saturday.
Figure 1. Morning visible satellite image of the Brazilian Invest 90Q.
Figure 2. Satellite-measured winds from ASCAT clearly show the circulation of the cyclone in this pass from 7:45 pm EST on March 9, 2010. Top winds as seen be ASCAT were 35 knots (40 mph), which is the minimum strength for a subtropical storm. However, this wind barb is pointing in the opposite direction to the rotation of the storm, and may be spurious. Image credit: NOAA/NESDIS/ORA.
Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's storm is located close to where Catarina formed.
cycloneye wrote:SL, 90, 2010031012, , BEST, 0, 297S, 476W, 40, 1000, LO
ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 010.invest
cycloneye wrote:SL, 90, 2010031012, , BEST, 0, 297S, 476W, 40, 1000, LO
ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 010.invest
MetSul Weather Center wrote:cycloneye wrote:SL, 90, 2010031012, , BEST, 0, 297S, 476W, 40, 1000, LO
ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 010.invest
40 mph or 40 kt ?
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