An Uneasy Future for Tropical Storm Emily

As of 5AM EDT, Tropical Storm Emily was located at 15.5N, 64.0W, moving W at 16 mph with sustained winds of 40 mph. It's central pressure was estimated to be 1006 mb. Satellite imagery shows that the convection around Emily's center continues to grow, with large amounts of cold anvil cirrus. However, satellite analysis of cloud-top winds suggest that Emily still has an elongated circulation, more like that of a jelly-bean than the compact circulation which is more favorable for intensification. Also, while Emily is in a low-shear region, there are large areas of wind shear to it's immediate north and south. The dry air of the Saharan Air Layer is just north of Emily, which would weaken the storm.


Figure 1 IR Satellite image of TS Emily taken at 3AM EDT August 2, 2011



Forecasting Emily
Model uncertainty is still high for forecasting Emily's track. The 00Z CMC and NOGAPS global models keep Emily on a western track, before recurving to make landfall on the western coast of Florida. The 00Z HWRF and GFDL dynamic
hurricane models both have Emily approaching the eastern coast of Florida, but recurving sharply to the northeast before making landfall. However, the premier global models, GFS and ECMWF, suggest that forecasters should be very cautious.
The 12Z ECMWF did not get a good representation of Emily in its starting conditions, so the forecast Emily did not gain strength and drifted westwards, missing Hispanola. The 00Z GFS does not have any forecast features that could be reasonably associated with Emily in my judgement. From what I can tell, the GFS moves Emily's circulation over Hispanola and Emily then never has a chance to organize. This is disconcerting since the previous 4 runs of the GFS had produced a reasonably robust tropical cyclone with winds near or just exceeding hurricane strength.

Even though the tracks produced by these models are different in their long-term outlooks, they all suggest that Emily will pass by Hispanola close enough for that island's mountains to impact the storm's winds and thus dampen any intensification. However, the 00Z NAM model does not bring Emily near the island, and keeps it moving westwards into the Caribbean sea as a well-organized storm. This, combined with the widely different solutions discussed previously, suggests that people across the Caribbean and living along the Gulf coast should keep an eye on this storm for the next several days.

I would prefer to make an intensity forecast for Emily after it has cleared the island of Hispanola and it's tall mountains. Many storms have weakened considerably after passing by there, and some have dissipated (TS Cindy in 1993, for example).

In light of this uncertainty, the NHC forecast hasn't changed that much. Emily is forecast to turn towards the northwest, making landfall somewhere in southeastern Florida on Saturday as a weak hurricane. (5AM EDT update NHC has adjusted their forecast to the east, so Emily does not make landfall in the next 5 days. Also, Emily does not reach hurricane strength in this forecast.) Tropical storm warnings have been issued for Puerto Rico and the Dominican Republic. A tropical storm watch has been issued for Haiti.


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

Angela will have a full post later today discussing Emily.

Thanks for reading,

Dr. Rob Carver