As Hurricane Katia traverse’s through cooler waters it appears that Katia is also having serious problems with dry air entrainment that is wrapping around from the southwest and into the inner eyewall along with moderate shearing. Katia is now a mid-category one storm and intensification is not indicated, in fact, the weakening process will continue for at least the next 24 hours. Due to the cooler SST’s any attempt to intensify with the shear decrease later in the forecast will be nullified by the SST’s. Once Katia begins the transformation to extra-tropical, Katia may slightly intensify, in 72- 96 hours during the transformation. Katia is heading NW at the moment but will be making the turn to the north within the next 24 hours and later turn to the NE while also accelerating and into the westerlies.
Tropical Depression Fourteen was upgraded to Tropical Storm Maria the 11am advisory from the NHC. As Hurricane Specialist Lixion Avila stated “…and yet another tropical storm in the Atlantic…” in the NHC Tropical Weather Outlook, it seems we are definitely in the peak of the hurricane season.
Tropical Storm Maria is heading just west of due west-northwest and the forward motion is currently at 23 MPH. If this continues, the Low-Level Circulation may out run the mid to upper levels of the convection. If so, Maria will have a very difficult time organizing and trying to intensify or at least it would be gradual. At the moment, the environment is not that conducive for further development as upper level winds in the 20-30 knot range may affect Maria but the overall pattern should allow for slow strengthening.
Although it is a little to early where Maria may head, the latest model runs with the exception of the BAMM (Shallow) tend to have Maria north of the Leeward Islands in several days. For what it’s worth, my own opinion is that the model are still a little biased to the north and although I believe the more turn to the WNW will happen, the more “western” track will happen before making the turn, thus this might be a much closer to the islands than forecast. As Katia leaves the scene, the sub-tropical ridge will want to build and keep Maria on that western track until finally heading on a more west-northwest track along the periphery of the southwestern edge of the ridge. A deep layered trough is forecasted by some of the models by 72 hours to be near the East coast of the US about the time Maria will be close or near the Leewards Islands. This trough should make Maria turn toward the NW and later to the north.
Invest 96L has been upgraded to Tropical Storm Nate as of the 5pm advisory from the NHC. Although Tropical Storm Nate had been “suggested” that it would develop to a at least a tropical depression, recon flew into the storm and found winds at flight level of 53 knots (un-flagged) or about 42 MPH at the surface, thus the storm was initiated as Tropical Storm Nate. As has been noted earlier, Nate has been drifting somewhat as the steering currents are quite weak. With the weak steering currents which may hang around for a few days, Nate will be in warm waters but there is vert dry air to the NW of Nate and this dry air (as been with many of the storms this year) may impact Nate later in the forecast period. Models at this time feel that Nate, in time, will be influenced by a developing ridge in the western Caribbean and making Nate turn to the west and into Mexico. Although this scenario may play out, if Nate moves further north, Nate will be north of the developing ridge and would then head toward the Gulf states or the Florida panhandle. It is just to early to say how this will play out with Nate.