Hurricane Gert is likely peaking in intensity as a category 2 hurricane, the strongest storm of the season so far. Gert was able to develop a well-defined eye and strengthen at an unusually high latitude – the strongest hurricane so far north by wind speed since Alex in 2004. Gert should transition into an extratropical cyclone by early on Friday. There are three tropical disturbances across the Atlantic Main Development Region (MDR) that have a chance to develop (including Invests 91L and 92L into tropical cyclones, and all are expected to take different paths if they develop). 91L is likely to take a southern track and could pose a threat to Honduras and the Yucatan Peninsula by early next week, possibly as a tropical storm. 92L could develop east of the Bahamas, and has a low chance of being a long-range threat to the United States. Another tropical wave to the east of 92L, which has not yet been designated an invest, has a chance to develop, but if development occurs, it will most likely recurve out to sea (with a possible long-range threat to Bermuda).

Hurricane Gert: Likely peaking in intensity, a weakening trend should begin tomorrow

As of 11:00 p.m. EDT Wednesday, Hurricane Gert was centered near, and was moving east-northeast at 37 mph. Maximum sustained winds were 90 knots (105 mph) with an estimated minimum pressure of 967 mb. Gert has maintained a fairly distinct eye for much of the day with Gert maintaining fairly cold cloud tops despite the fact that the hurricane is beginning to move over cooler sea surface temperatures of about 26°C (78.84°F), and should cross the isotherm later tonight. Gert will also be moving into an enviornment increasingly strong wind shear, and this should cause rapid weakening tomorrow and eventually extratropical transition by Friday.

Invest 91L: Could develop near the Lesser Antilles or over the Caribbean Sea

As of 00:00 UTC Thursday, Invest 91L was centered near 13.5°N 50.4°W, and was moving westward at about 15 to 20 mph. Maximum sustained winds were 25 knots (30 mph) with an estimated minimum pressure of 1010 mb. The National Hurricane Center (NHC) gives 91L a 50 percent chance of development within 48 hours, and a 60 percent chance of development within five days. The circulation of 91L has become better defined today, but the convective activity is still quite sparse due to some dry air around the system. Although 91L is expected to remain in a low-shear environment throughout the forecast period as it enters the Caribbean Sea with increasing mid-level moisture and sea surface temperatures, strong trade winds will likely limit significant organization and strengthening in this part of the Caribbean. If 91L can manage to remain north of Honduras by early next week, it will have a better chance to strengthen over the Northwestern Caribbean. If it cannot gain enough latitude, it will likely remain weak due to land interaction with Central America. The 18z Wednesday GFS model run, as well as the 12z Wednesday ECMWF, UKMET and CMC model runs, predicted development of 91L. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate 91L tomorrow, if necessary. Barbados, the Windward Islands, Central America and the Yucatan Peninsula should monitor the progress of 91L. 91L is not expected to be a threat to the United States.

Invest 92L:  A narrow opportunity for development before conditions are expected to become unfavorable

As of 00:00 UTC Thursday, Invest 92L was centered near 14.3°N 38.6°W, and was moving west-northwestward at about 15 to 20 mph. Maximum sustained winds were 25 knots (30 mph) with an estimated minimum pressure of 1009 mb. The NHC gives 92L a 40 percent chance of development within 48 hours, and a 50 percent chance within five days. Much like 91L, 92L has plenty of spin, but the convective activity is not that well organized. Some slight development is possible with 92L by this weekend. Upper-level winds are then expected to become less conducive, but could become a little more favorable for development by early next week when 92L could be near the Bahamas. Most global models supported some limited development of 92L. Although global models do not currently indicate such a scenario, 92L will need to be watched for possible development near the Bahamas or perhaps even over the Gulf of Mexico if it manages to survive until that point as a trackable entity.

Wave off Africa: Not likely to develop in the short term, but could develop by the weekend or early next weekend

Another tropical wave exited the coast of Africa early Wednesday, but convective activity has significantly waned since the wave emerged into the Atlantic. The NHC gives this wave a near zero percent chance of development over the next 48 hours, and a 40 percent chance over the next five days. The ECMWF, UKMET, and CMC models are suggesting that this wave could develop into a tropical cyclone by early next week, with the chance of it becoming a hurricane over the subtropical Atlantic. This wave does not appear likely to be a threat to the United States, but it could pass close to Bermuda in the long range.

The next three names on the Atlantic naming list are Harvey, Irma and Jose. I believe we will see at least one of the three systems become named by this weekend.

I will be back tomorrow with another post on these systems.