Tropical Storm Emily Approaches Hispaniola

As of 8PM EDT, Tropical Storm Emily was located at 16.2N, 66.7W, moving WNW at 14 mph with sustained winds of 50 mph. It's central pressure was estimated to be 1005 mb. Tropical storm warnings are in effect for Puerto Rico, the Dominican Republic, Haiti, the southeast Bahamas, and the Turks and Caicos islands.

2AM EDT Update
As of 2AM EDT, Tropical Storm Emily was located at 16.3N, 67.5W, moving WNW at 13 mph with sustained winds of 50 mph. It's central pressure was estimated to be 1006 mb. Tropical storm warnings are in effect for Puerto Rico, the Dominican Republic, Haiti, the southeast Bahamas, and the Turks and Caicos islands.
End update

Satellite imagery shows a large amount of convection near Emily's center. However, the NHC discussion suggests that Emily is not standing straight up, like an ideal tropical cyclone, but the circulation is tilted eastwards with height. This is due to the wind shear present over the storm.


Figure 1 IR Satellite image of TS Emily taken at 11PM EDT August 2, 2011



Forecasting Emily
The fog of uncertainty still shrouds Emily's track forecast. The 12Z ECMWF and NOGAPS models keep Emily on a west to west-northwest track that skirts the southern edge of Hispaniola before running along the length of Cuba. The 12Z CMC global model has Emily tracking towards the NW, but recurving before making landfall along the US coastline. The 12Z and 18Z GFS runs (as shown in Figure 2), agree on a roughly similar track.


Figure 2 Peak winds (mph) over the next week from the 18Z GFS

The 12Z UKMET global model, and the 18Z GFDL and HWRF dynamical models are west of the GFS/CMC consensus track, withe the GFDL keeping Emily over the western Bahamas. The HWRF and UKMET tracks stay very close to the Florida/Georgia coastlines.

However, all of these tracks require Emily's circulation to grow tall enough that the upper-level steering winds can pull Emily towards the NW. I've discussed the situation with Angela Fritz, and she thinks that if Emily's circulation remains shallow, a more westerly track like that described by the ECMWF and NOGAPS could be more likely.

If we look at the previous NHC forecast, Emily was expected to be at 15.9N, 66.5W at the time of the forecast update. This is approximately 25 miles southeast of Emily's current position. If we ignore the uncertainty of locating Emily's center, this suggests that the westerly ECMWF/NOGAPS track is less likely, but doesn't say much about deciding between the GFS/GFDL and UKMET/HWRF tracks.

My opinion about forecasting Emily's intensity has not changed from this morning's update. I would prefer to wait for Emily after it has cleared the island of Hispanola and it's tall mountains. If Emily's circulation can survive the 8000 feet tall mountains of Hispaniola, the sea is warm enough for moderate intensification.

Having taken all of this into consideration, the 5 day NHC track forecast splits the difference between the HWRF/UKMET and GFS/GFDL tracks, bringing Emily over the central Bahamas before recurving towards the northeast. Emily is also forecast to become a hurricane on Sunday, August 7. However, it is important to remember that NHC has said that the forecast uncertainty after 48 hours is larger than usual for Emily. So, people living on the East Coast should still not think they are in the clear just yet.

In terms of immediate impacts, 4-6 inches of rain are expected over Puerto Rico, Haiti, and the Dominican Republic, with 10 inches possible in isolated areas.


Figure 2 Official five-day track forecast for Tropical Storm Emily.

Eastern Pacific

Eugene is now the third major hurricane of the Eastern Pacific season with estimated winds of 115 mph. However, Eugene is well out to sea and should not threaten any landmasses. Invest 97E has a 70% chance of becoming a tropical disturbance in the next 48 hours, but will likely not affect any land areas.

Angela will have a full post Wednesday morning discussing Emily.

Thanks for reading,

Dr. Rob Carver