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Caribbean Disturbance 92L Organizing; Typhoon Utor Hits China

By: Dr. Jeff Masters, 12:40 PM GMT on August 14, 2013

Pressures are falling in the Western Caribbean where a tropical wave (92L) is headed northwest at 10 - 15 mph. Cayman Islands radar shows that the thunderstorm activity is disorganized, and satellite loops show only a modest area of heavy thunderstorms, and no signs of a surface circulation. Wind shear is a moderate 10 - 20 knots over the the wave, which should allow slow development today. The 00Z SHIPS model forecast predicts that 92L will remain in an area of low to moderate wind shear through Friday, but then shear will rise on Saturday. If a tropical depression or tropical storm does form, and its circulation extends high above the surface, a trough of low pressure over the northern Gulf of Mexico would likely steer the storm northwards to a landfall between Eastern Louisiana and the Florida Panhandle. This is the solution presented by the 06Z run of the GFS model. It shows a landfall on Saturday of a weak tropical storm between Eastern Louisiana and the Florida Panhandle. The Navy's 00Z run of the NAVGEM model shows a more westerly path for 92L, with the storm eventually coming ashore near the Texas/Mexico border. The European model keeps 92L weak and does not develop it. The more northwards path advertised by the GFS model would bring a large amount of moisture into the Southeast U.S., resulting in a large area of 4+" of rain. In their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave the system a 50% of developing by Friday, and a 60% chance of developing by Monday. The Hurricane Hunters are on call to investigate the system on Thursday, if necessary.

Figure 1. Morning satellite image of Invest 92L over the Western Caribbean, taken at 10:31 am EDT August 14, 2013. Image credit: NASA/GSFC.

New African Tropical Wave 93L Organizing
A tropical wave that pushed off the coast of Africa on Tuesday (93L) is showing a modest amount of heavy thunderstorm activity and spin on satellite loops as it heads west-northwest at 10 mph. The wave is over warm waters of 28°C and is under a moderate 10 - 15 knots of wind shear, which should allow continued development today and Thursday. The 00Z SHIPS model forecast predicts that wind shear will be low to moderate for the next five days, which favors development. However, the waters beneath 93L will steadily cool to a marginal 26°C by Friday, and the atmosphere will steadily get drier, as 93L encounters the Saharan Air Layer (SAL), discouraging development. In their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave the system a 60% of developing by Monday, and a 60% chance of developing by Friday. The expected west-northwest track of 93L over the next five days will carry it into a region of ocean where it is uncommon for tropical cyclones located there to eventually impact any land areas except Bermuda.

Figure 2. Radar image of Typhoon Utor as it was closing in on the coast of Southeast China at 10:42 am local time on August 14, 2013. At the time, Utor had top winds of 100 mph. Image credit: Meteorological Bureau of Shenzhen Municipality.

Figure 3. MODIS satellite image of Typhoon Utor taken at 05:45 UTC on Wednesday, August 14. At the time, Utor was a Category 1 storm with 90 mph winds, and was making landfall in China, 150 miles southwest of Hong Kong. Image credit: NASA.

Typhoon Utor hits China
Typhoon Utor hit Southeast China about 150 miles southwest of Hong Kong near 3 pm local time this Wednesday, as a Category 1 storm with 90 mph winds. The typhoon brought sustained wind of 34 mph, gusting to 44 mph to Macao, and wind gusts as high as 54 mph to Hong Kong. Widespread heavy rains are falling across much of Southeast China, as seen on Hong Kong radar and China radar. Utor will continue to dump torrential rains capable of causing deadly flash floods and mudslides over much of Southeast China and Northern Vietnam over the next three days. Satellite imagery shows that Utor is a large but weakening typhoon, with the eye no longer visible. In the Philippines, where Utor hit as a Category 4 storm with 140 mph winds on Monday, 4 deaths are being blamed on the storm, and 11 people are missing.

Jeff Masters


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