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 , 7:50 AM GMT on August 31, 2009
Hi, this is Dr. Rob Carver filling in for Dr. Masters. Hurricane Jimena is the main story for the North American tropics with satellite-estimated winds of 145 mph. This makes Jimena a Category 4 storm on the Saffir-Simpson scale. However, later today, we will actually have measured winds for this storm. The Plan of the Day indicates that an Air Force reconnaissance mission to Jimena has been scheduled for the middle of the day Aug. 31. Hurricane watches have been posted for the southern Baja peninsula.
Jimena continues to have an impressive presentation on satellite with a compact core and cold cloud tops. Late in the afternoon, the TRMM satellite flew directly over Jimena, and part of the central core was in the field of view of TRMM's radar.
Fig. 1 TRMM overpass at 2355Z Aug 30 showing surface rain fall rates derived from microwave radiometry and Doppler radar. Image courtesy of NRL
This shows that Jimena has a a very tight eyewall, consistent with its intensity, with a possible eyewall replacement cycle starting soon. If the cycle starts, Jimena will likely weaken some, but this is still a dangerous storm. The AF reconnaissance mission will provide NHC's forecasts a good deal of information about the storm and improve the computer forecasts (There really isn't much in the way of measurements out there.) It is also important to note that as Jimena moves northward, it will move over cooler water, which is not favorable for maintaining its intensity.
The current track forecast calls for Jimena to make landfall on the western coast of Baja southwest of La Paz. Given the angle between Jimena's track and Baja's coastline, there is a wide spread of possible landfall locations. People living in this area need to be making hurricane preparations now.
Invest 94L Invest 94L is still out there, moving westwards to the Lower Antilles. People in the Lesser Antilles still need to keep an eye on this storm, as tropical storm formation is possible with this storm. This is still considerable uncertainty on the track of this feature as different models have different initializations of the storm. However, the Plan of the Day indicates that reconnaissance missions into Invest 94L could start as soon as Tuesday, September 1, which would give everybody more data to understand what's going on.
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