Litte Change to--or Threat From--Atlantic Invests 92L, 93L, and 94L

An area of low pressure (Invest 92L) with a well-defined surface circulation was located a few hundred miles west of the Florida Keys on Saturday morning. Satellite images and long range radar out of Key West showed that 92L had a well-defined surface circulation center, but the center was completely exposed to view, with almost no heavy thunderstorms—the telltale sign of a storm struggling with dry air and high wind shear. The storm’s heaviest thunderstorms were being kept to the southeast side of the center of circulation by high wind shear of 20 - 30 knots, due to strong upper-level winds out of the northwest. The disturbance was also battling plenty of dry air, as seen on water vapor satellite loops, and the 8 am EDT Saturday run of the SHIPS model showed the humidity at mid-levels of the atmosphere was about 60%, which is marginal for tropical storm formation. Sea surface temperatures (SSTs) were a very warm 30°C (86°F), though.


Figure 1. Latest satellite image of 92L.

Forecast for 92L
There is little model support for the development of 92L, with none of the 00Z Saturday operational versions of our three reliable models for predicting tropical cyclone genesis--the GFS, UKMET and European models--predicting development. During the next five days, 92L should experience dry mid-level air with a relative humidity of 55 - 65%, and see moderately high wind shear of 15 - 25 knots, as the storm heads west at about 5 mph through the southern Gulf of Mexico, according to the 8 am EDT Saturday run of the SHIPS model. These conditions are quite marginal for development. In their 8 am EDT Saturday Tropical Weather Outlook, NHC dropped their 2-day and 5-day development odds to 10%.

Tropical wave 93L just north of Puerto Rico little threat to develop
An area of low pressure (Invest 93L) located about 200 miles north of Puerto Rico on Saturday morning was headed west-northwest at about 15 mph. Satellite images show that 93L continues to have only a limited amount of heavy thunderstorms, with no sign of a surface circulation center. The disturbance was battling plenty of dry air, as seen on water vapor satellite loops. The 8 am EDT Saturday run of the SHIPS model showed the humidity at mid-levels of the atmosphere was about 45 - 50%, which is almost always is too dry to support tropical storm formation. Conditions were otherwise favorable for development, with wind shear a low 5 - 10 knots, and sea surface temperatures (SSTs) a warm 29.5°C (85°F.)


Figure 2. Latest satellite image of 93L.

Forecast for 93L
There is very little model support for the development of 93L, with none of the 00Z Saturday operational versions of our three reliable models for predicting tropical cyclone genesis--the GFS, UKMET and European models--predicting development. The 8 am EDT Saturday run of the SHIPS model predicted that 93L would find a moister surrounding atmosphere by Sunday, but that wind shear would increase to the moderate range. These conditions are quite marginal for development. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave this system 2-day and 5-day development odds of 10%. Invest 93L will continue moving west-northwest to northwest at about 15 mph through Sunday, then slow down to a forward speed of about 10 mph on Monday and Tuesday. This should put the storm near the coast of northern Florida by Tuesday.


Figure 3. Latest satellite image of 94L.

Tropical wave 94L in the central tropical Atlantic likely to develop
A large tropical wave located about 1000 miles east of the Lesser Antilles Islands on Saturday morning (Invest 94L) was headed west-northwest at 10 mph. Satellite images showed that 94L remained well-organized, with a large circulation and an increasing amount of heavy thunderstorms. With wind shear expected to be in the low to moderate range through Monday, along with plenty of warm water and a moist atmosphere with 70% humidity at middle levels of the atmosphere, 94L is likely to develop into a tropical depression by Monday, as predicted by our top three models for hurricane genesis, the UKMET, GFS and European models. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave this system 2-day and 5-day development odds of 70% and 90%, respectively. The long-range models are showing 94L will likely be a “fish storm”, and take a west-northwesterly then northwesterly track into the Central Atlantic to a location where few storms ever become a threat to the Lesser Antilles Islands or North America. The next name on the Atlantic list of storms is Ian.

Tropical Storm Meranti headed for Taiwan
In the Northwest Pacific, Tropical Storm Meranti is intensifying and is expected to become a major typhoon that will threaten Taiwan by Wednesday. We’ll have more on this storm in future posts.

Jeff Masters