Tropical storm Emily: Will it intensify and threaten East Coast?

Tropical storm Emily at 11 a.m. (NOAA) Since it formed last night, tropical storm Emily has struggled to get its act together. Positioned 270 miles southeast of San Juan this morning, the storm has “meandered” over the last few hours according to the National Hurricane Center, but is expected to pick up the pace and head west northwest at 12 mph later today. A minimal tropical storm, Emily’s maximum sustained winds are 40 mph.

Tropical storm warnings are in effect for Puerto Rico, the Dominican Republic and Haiti, with a tropical storm watch over the U.S. Virgin Islands.

Intensity forecast

For the last day, Emily has been fighting a layer of Saharan dry air. Capital Weather Gang’s tropical weather expert Greg Postel said the intensity of the dry air is “at the top end of the scale.”

However, Emily has recently acquired a more healthy looking satellite appearance, with deep convection firing up near the center. Postel said it’s not clear whether this a temporary development or indication of an intensifying storm. If the storm can sustain the core of deep convection longer than half a day, Postel said its intensification prospects would markedly improve. The storm would also be favored to grow stronger if it takes a more southerly track, providing more separation from the dry air layer while keeping it away from the hostile land terrain of Hispaniola (Dominican Republic and Haiti).

If the storm can fend off or avoid the dry air, sea surface temperatures are warm and wind shear is low, so Postel and the National Hurricane Center forecast some intensification to strong tropical storm or possibly low-end hurricane intensity. No computer model projects that Emily will strengthen into a major hurricane.

Track forecast

National Hurricane Center track forecast for EmilyThe official National Hurricane center track takes Emily across the Caribbean and over Haiti towards the central Bahamas in the Atlantic. The East Coast of Florida is on the west side of the “cone of uncertainty” with coastal Georgia and South Carolina on the north side. At this point, Postel called a U.S. landfall “a realistic scenario” but stopped short of calling it likely.

In fact, the latest GFS model curves Emily out to sea before it can strike the U.S. coast. Another scenario, favored by the European model, has Emily undercutting the big heat dome over the southern U.S. tracking it due west towards Central America.

Generally speaking, the stronger the storm gets, the more likely it is to turn north, whereas a weaker storm would probably take a more southerly track (but perhaps allowing for more strengthening later on if the storm remained over water).

As the storm has shown signs of improved organization, Postel favors a more northerly track over Hispaniola into the vicinity of the Bahamas rather than due west across the Caribbean. Once the storm reaches the Bahamas, uncertainty is large and a U.S. landfall or out to sea track are both plausible

We will have a full update tomorrow.

Related: 2011 Hurricane Tracking Center