The Atlantic tropics are very busy today, with Florence becoming the third hurricane of the season, Tropical Storm Gordon nearing landfall near the Alabama-Mississippi border, and two more tropical waves (including Invest 92L) are likely to develop by this weekend. The peak of the season is here, and the Atlantic is likely to remain quite busy for the next couple weeks.

Gordon likely to make landfall as a strong tropical storm in a couple hours

Tropical Storm Gordon has failed to strengthen significantly since yesterday, and both reconnaissance aircraft and surface observations continue to indicate that Gordon remains just below hurricane strength. As of 7:00 p.m. CDT (8:00 p.m. EDT) Tuesday, Tropical Storm Gordon was centered near 29.7°N 87.9°W, and was moving northwestward at about 14 mph. Maximum sustained winds were 60 knots (70 mph), with an estimated minimum pressure of 999 mb. Due to moderate wind shear and its fast forward speed, Gordon has been unable to strengthen quickly. Gordon is not a particularly well organized storm, and winds are quite weak outside of the northeast quadrant. Although some slight intensification cannot be ruled out before landfall in a couple hours, the window for Gordon to become a hurricane is likely closing.

A Hurricane Warning remains in effect from the Mouth of the Pearl River to the Alabama-Florida Border. A Tropical Storm Warning is in effect from West of the Mouth of the Pearl River to the Mouth of the Mississippi River, including Lake Pontchartrain, as well as the Alabama-Florida Border to Okaloosa-Walton County Line. A Storm Surge Warning is in effect from Shell Beach to Dauphin Island. A Storm Surge Watch is in effect from West of Shell Beach to the Mouth of the Mississippi River, and East of Dauphin Island to Navarre. It is possible the hurricane warnings may be discontinued soon since it is appearing less likely that Gordon will bring hurricane conditions to any location. The primary threat with Gordon is likely going to be storm surge and rainfall, the latter of which could exceed 12 inches in isolated areas.

Florence a hurricane, too soon to tell if it will affect any land areas

On Tuesday morning, Hurricane Florence strengthened into the third hurricane of the 2018 Atlantic hurricane season. Since that time, the hurricane has continued to become better organized, with an eye feature appearing in satellite images. As of 5:00 p.m. EDT Tuesday, Hurricane Florence was centered near 20.3°N 43.2°W, and was moving west-northwestward at about 12 mph. Maximum sustained winds were 75 knots (85 mph), with an estimated minimum pressure of 984 mb. Although Florence is beginning to move over gradually warmer water temperatures, moderate wind shear of about 20 knots is expected to continue for the next few days. Florence is also currently in a fairly dry air mass, with mid-level relative humidity values of near 50 percent. Most of the model guidance, including both statistical and global models, shows Florence weakening later this week due to the shear. Considering Florence has intensified somewhat unexpectedly despite the shear, it would not be surprising if Florence maintains hurricane intensity throughout the forecast period. In about five days, wind shear could decrease while sea surface temperatures warm to around 29°C, and re-intensification is likely at that time. It is possible that Florence could become a major hurricane over the western subtropical Atlantic in a week or so.

Although the most likely outcome is that Florence recurves out to sea with no direct impacts in the United States, it is still too soon to definitively determine Florence’s future track. It is also possible that Florence could pass very near Bermuda next week.

Invest 92L expected to develop, another wave behind 92L may also develop this weekend

There are two tropical waves that will need to be monitored for tropical cyclogenesis later this week and into this weekend.

The first, Invest 92L, is currently located over the eastern tropical Atlantic. Gradual development is expected, and 92L is likely to become a tropical depression later this week. The National Hurricane Center (NHC) gives 92L a 40 percent chance of development within 48 hours, and a 90 percent chance within five days. As of 18:00 UTC Tuesday, Invest 92L was located near 10.0°N 24.4°W. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1007 mb. Although shower and thunderstorm activity is currently limited with 92L, this activity should begin to increase later this week as 92L enters a more favorable environment. The 12z Tuesday GFS, ECMWF and UKMET models all showed at least some weak development with 92L. It is too soon to determine if 92L will affect any land areas.

The second is a tropical wave that is expected to emerge off the coast of Africa late Thursday or Friday. The NHC gives this wave a near zero percent chance of development within 48 hours, and a 20 percent chance within five days. Both the ECMWF and GFS models are aggressive on developing this wave, though this one is less likely to affect land areas than 92L.

The next two names on the Atlantic naming list are Helene and Isaac.