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The Tropics Are Waking Up (29 AUG 2016)

  POSTED ON: Monday, August 29, 2016 12:23 PM by Meteorologist A.R. Davies

The Atlantic Ocean has seen an uptick in tropical activity over the last week and that trend is expected to continue over the next two weeks (or more).  The image below from the National Hurricane Center (NHC) shows the locations of three tropical systems in the Atlantic Ocean basin as of 1100 EDT on Monday, August 29, 2016. Fortunately, the most powerful of the three storms, Category 2 Hurricane Gaston, is located about 560 miles east of Bermuda and will stay away from the United States.

NHC current tropical systems

Tropical Depression Eight is currently off the U.S. Southeast coast and the latest models suggest it will strengthen into a fairly weak and disorganized Tropical Storm by Tuesday morning. At this time, it remains unclear if the storm will actually make landfall, but if it does, it will likely occur late Tuesday night or early Wednesday morning along the Outer Banks of North Carolina. Regardless of whether the storm makes landfall, the Outer Banks should prepare for the possibility of 30 to 45 mph sustained winds out of the north/northeast between 1600 EDT on Tuesday and 0400 EDT on Wednesday. As rain bands come onshore, gusts could peak around 50 mph during this time period.  Generally, 1.0-3.0 inches of rainfall is expected across the Outer Banks with localized totals toping 3.0 inches. The storm surge will likely be fairly small (1.0-2.0 feet) with 4.0-6.0 foot waves (and rip currents).   The image on the left below shows the NHC storm track as of 1100 EDT on August 29.  The yellow shaded region indicates where Tropical Storm Watches have been issued. The image on the right shows the simulated radar at 0200 EDT on Wednesday morning from the Hurricane WRF model.  In the simulation, the storm is weak with the center of circulation located over Hatteras Island, NC.

TD 8

Meanwhile, Tropical Depression Nine is about 170 west southwest of Key West, FL as of 1100 EDT on Monday.  At this time, the official NHC forecast suggests the storm will be a strong Tropical Storm (max winds near 60 mph) by landfall on Thursday (left image below).  With that said, some of the high resolution hurricane models, including the Hurricane WRF model, suggest the storm could develop into a hurricane before making landfall. The image to the right below shows the simulated radar from the Hurricane WRF model at 0800 EDT on Thursday; at that forecast time, the model projects the storm will have developed into a well defined hurricane with the center of circulation northwest of Tampa, FL.  Regardless of whether the storm develops into a hurricane or not, the Florida Gulf Coast should expect heavy rain (upwards of 5.0 inches widespread), significant waves/rip currents, and gusty winds over the next 24 to 36 hours.  As the storm approaches land, the conditions will likely worsen for locations within the storm path. No watches or warning have been posted at this time, but closely monitor updated information from the National Weather Service and National Hurricane Center.

TD 9

Looking ahead, tropical activity is expected to remain high over the next two week.  Most major models suggest at least one (if not multiple) tropical systems could develop across the Atlantic Ocean basin later this week or early next week. The figure below on the left shows the Global Tropical Hazards Outlook issued by the National Weather Service Climate Prediction Center.  The red shading indicates where new tropical cyclone development is possible over the next seven days.  One (of many) reasons for the increase in tropical activity in the Atlantic Ocean is the anomalously warm sea surface temperatures (SSTs) right now.  As shown in the figure below (right), SSTs are running 0.5 to 1.5 oC above normal across the western Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.  This is significant because tropical storms pull most of their energy from warm ocean water.  

While it is too early to say for sure if more storms will develop (and if so, where they will go), the probability of additional tropical cyclone develop over the next week or so seems high.  Stay tuned.

 looking ahead

ISSUED: 29 August 2016 at 1230
FORECASTER: Meteorologist A.R. Davies
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Category: General Interest

Alexander R. Davies

Meteorologist
Oceanography Department, USNA
  adavies@usna.edu
  410-293-6565