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99L likely to develop over the Caribbean; 90L over the Atlantic
By: Civicane49 , 2:02 AM GMT on October 21, 2012
A low pressure system associated with a tropical wave is over the central Caribbean Sea, well south of Haiti. It has been classified as Invest 99L. Recent satellite image reveals that the disturbance has an appearance of a developing tropical cyclone. 99L has a well-organized cloud structure; however, it is lacking deep thunderstorm activity in the center due to diurnal minimum. Nevertheless, diurnal maximum and favorable conditions should allow it to increase by early tomorrow. Surface observations near the system report decreasing surface pressures. Moreover, satellite and surface data are also indicating that a surface circulation is becoming better defined. UW-CIMSS analysis depicts that wind shear is low and an upper-level anticyclone develops over the tropical disturbance. 99L will likely become a tropical cyclone by the next day or sooner. Reconnaissance aircraft is scheduled to investigate this system tomorrow to obtain detailed information of the tropical disturbance.
Figure 1. Evening infrared satellite image of Invest 99L. Image credit: NOAA/RAMMB.
Forecast for 99L
99L is expected to become a tropical cyclone by tomorrow or so. There are many model supports for further development. Environmental conditions are expected to remain very favorable for 99L over the next several days. The system is forecasted to remain over warm sea surface temperatures and high Tropical Cyclone Heat Potential (TCHP) values. Wind shear is forecasted to remain in low to moderate range through 72 hours. The atmospheric environment is forecasted to remain moist over the next several days. Given the fact that 99L will be in very favorable conditions, I would not be surprised if the system eventually becomes a hurricane. Based on the current trends, I give this system a 70% chance of becoming a tropical cyclone in the next two days. The system is anticipated to move westward slowly over the next couple of days. Thereafter, the system may meander over the Caribbean Sea for few days before a strong trough of low pressure allows it to turn northward over Cuba and the Bahamas. However, there is some uncertainty of the forecast path of 99L in several days and beyond.
Interests in Hispaniola, Jamaica, the Cayman Islands, Cuba, and the Bahamas should monitor the system very closely over the next several days as it is forecasted to bring some very heavy rain and gusty winds. These heavy rains could produce deadly floods and mudslides.
Figure 2. Latest Tropical Cyclone Heat Potential (TCHP) in the Caribbean Sea. Notice that red colors represent areas of extremely high TCHP, which indicates that warm waters extend with great depth in the ocean. These features are usually beneficial for tropical cyclones to rapidly strengthen. Image credit: NOAA/AOML.
90L over the Atlantic
Over the open Atlantic, there is another tropical wave situating about 1000 miles east-northeast of the northernmost Lesser Antilles. The system has been classified as Invest 90L. The wave is associated with an upper-level low, which is slowing development of 90L. Latest satellite image depicts that shower and thunderstorm activity has diminished. 90L is forecasted to move northwestward over the next few days and later turn northward and eventually northeastward. It is not anticipated to threaten any land areas. Environmental conditions are forecasted to become slightly more favorable for further development. Although wind shear is currently high over 20 knots, it is forecasted to decrease below 20 knots through 48 hours before increasing again. Sea surface temperatures are expected to remain warm. However, many models are showing little to no development of the disturbance. I give this system a 30% chance of developing into a tropical or subtropical cyclone in the next 48 hours.
Figure 3. Evening infrared satellite image of Invest 90L. Image credit: NOAA/RAMMB.
Over the eastern Pacific, an area of disturbed weather is concentrated just south of the Gulf of Tehuantepec. Recent satellite image shows that it remains fairly disorganized. Environmental conditions appear relatively favorable for further development in the next few days. Some global models, including the CMC and the GFS, are forecasting it to develop into a tropical cyclone by the next four to five days. I give this system a 10% chance of becoming a tropical cyclone in the next two days. The system is forecasted to move westward over the next several days before recurving towards Mexico. The remnants of it are forecasted to move into the Gulf of Mexico. At this time, it is unknown that it will redevelop over the Gulf.
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