Tropical Storm Franklin Develops in NW Caribbean

The sixth tropical storm of the 2017 Atlantic season was gaining strength late Sunday as it headed toward a landfall on the Yucatan Peninsula late Monday. Tropical storm warnings were in effect for most of the Yucatan Peninsula coastline of Mexico, with a tropical storm watch southward on either side of the peninsula, including the northern Belize coast.

Franklin was designated a tropical storm by the NOAA/NWS National Hurricane Center at 11 pm EDT Sunday, when the storm was located only about 100 miles north of the northeast tip of Honduras. A NOAA buoy northeast of the center reported sustained winds of minimal tropical storm strength, 35 knots (40 mph). Showers and thunderstorms (convection) were blossoming around Franklin’s newly consolidated center late Sunday, and an increasing amount of spin was evident in satellite loops. The center of Franklin is far enough north of the Honduras coast to minimize land interactions as the storm continues on its west-northwest course, moving at about 13 mph. Computer forecast models are in strong agreement on Franklin’s path, which should curve gently to the left as the storm moves across the Yucatan peninsula and into the Bay of Campeche.

Figure 1.  WU depiction of NHC tracking map for Tropical Storm Franklin as of 11 pm EDT Sunday, August 6, 2017. There is potential for Franklin to reach hurricane strength between the 12 AM Thursday and 12 AM Friday positions, as discussed below.

Intensity outlook for Franklin

The intensity outlook for Franklin has changed little from our detailed report on Sunday afternoon. Franklin will likely reach the Yucatan as a strong tropical storm. An intensification to Category 1 hurricane strength just prior to landfall cannot be ruled out, given the very warm waters east of the Yucutan, the high oceanic heat content there, and the expected lessening of wind shear around Franklin on Monday. A Hurricane Hunter flight into Franklin has been scheduled for midday Monday. On its expected track, the highest winds from Franklin would most likely affect the sparsely populated southern part of Mexico’s Quintana Roo state, but gales may extend well northward along the coast. Torrential rains of 3” - 6” or more can be expected across the region.

Franklin’s trek across the flat terrain of the Yucatan should have only a minor dampening effect, and the storm is liable to intensify further when it reaches the warm waters of the Bay of Campeche. The official NHC forecast at 11 pm EDT Sunday called for Franklin to arrive at the northeast coast of Mexico on Thursday morning. Our best model for intensity forecasts, the HWRF, has been consistent in projecting that Franklin could be a Category 2 hurricane by the time of this second landfall, and the 0Z Sunday SHIPS model output indicates a 58% chance that Franklin will become a 100-knot hurricane (Category 3) while in the Bay of Campeche. Because the official NHC forecast provides intensities at 72- and 96-hour intervals, it does not include a predicted strength in between those points, during the 12 hours on either side of Franklin’s second landfall (which is expected around the 84-hour point). Overall, it appears that odds favor at least a Category 1 landfall in northeast Mexico on Thursday.

We’ll be back with an update on Franklin and other tropical developments around midday Monday.