Invests 90L and 99L over the Atlantic have not become any better organized today, but remain threats to develop into tropical cyclones over the next several days. In the Eastern Pacific, Invest 91E somewhat unexpectedly developed into Tropical Depression Eleven-E this morning, but is not expected to strengthen due to a hostile environment.

Invest 99L likely to develop, but long-term future extremely uncertain

Invest 99L has not become much better organized today as it struggles to consolidate due to its large size. As of 00:00 UTC Saturday, Invest 99L was centered near 9.8°N 31.0°W and was moving west-northwestward at about 15-20 mph. Maximum sustained winds were 25 knots (#0 mph) with an estimated minimum pressure of 1010 mb. 99L is currently disorganized, with only limited shower and thunderstorm activity. The National Hurricane Center (NHC) gives 99L a 50 percent chance of development within 48 hours, and an 80 percent chance within five days. 99L is currently located in a marginally favorable environment, with sea surface temperatures near 27-28°C (82.4-84.2°F), mid-level relative humidity values of 65-70 percent, and wind shear is light to moderate at 10-15 knots.

Global model support for 99L is not as strong as it was yesterday. The 12z Friday ECMWF operational model run did not predict much, if any, development of 99L, although several EPS ensemble members did develop it into a weak tropical cyclone. The 12z Friday UKMET model run predicted that 99L would not develop until the middle of next week. The 18z Friday GFS model run predicted more rapid development, predicting 99L would develop into a tropical depression by Monday and approach the Northern Lesser Antilles as a tropical storm by next Thursday. Several GEFS ensemble members also indicated this possibility. The 12z Friday CMC model run predicted that 99L would quickly develop and recurve out to sea as a hurricane, but this model is typically not accurate for tropical cyclones. It seems unlikely that 99L will be able to develop into a strong tropical cyclone before approaching the Lesser Antilles, perhaps due to some dry air from the Saharan Air Layer (SAL). It is still too soon to predict the long range future track and intensity of 99L since a well-defined circulation center has not formed, but the Northern Lesser Antilles should monitor the progress of 99L closely. It is possible that 99L could come close to Hispaniola in a week or so, which would likely disrupt organization. However, if 99L is able to stay north of Hispaniola intact, it will need to be watched as a possible threat to the United States. A recurve out to sea is currently looking less likely because development is not expected to be imminent, and the Bermuda-Azores ridge is strong.  I give 99L a 40 percent chance of development within the next 48 hours, and a 70 percent chance during the next five days, slightly lower than the NHC’s odds, mainly due to the negative signal from the ECMWF.

Invest 90L could develop in Western Caribbean or Bay of Campeche with favorable conditions

A tropical wave, designated Invest 90L, over the Central Caribbean Sea is producing some disorganized showers and thunderstorms. As of 00:00 UTC Saturday, Invest 90L was centered near 13.2°N 73.1°W and was moving west-northwestward at about 15 mph. Maximum sustained winds were 25 knots (30 mph) with an estimated minimum pressure of 1009 mb. 90L is expected to emerge into the Northwestern Caribbean Sea by early next week, where conditions are expected to be conducive for development. 90L is currently in a historically unfavorable area to develop, known as the Caribbean “graveyard,” due to strong trade winds. 90L is expected to cross the Yucatan Peninsula by Tuesday and emerge into the Bay of Campeche by Wednesday. However, when 90L emerges into the Northwestern Caribbean Sea by early next week, wind shear is expected to drop below 10 knots, while sea surface temperatures warm to over 30°C and mid-level relative humidity values are expected to increase to over 75 percent. The 18z Friday GFS model run predicted that 90L would only slightly develop into a weak closed low over the Bay of Campeche. However, the 12z Friday ECMWF and CMC model runs predicted that 90L could develop in the Northwestern Caribbean and strengthen to near hurricane strength in the Bay of Campeche. Many EPS ensemble members also showed development. However, the 12z Friday UKMET model did not show any development. Conditions in the Bay of Campeche could be favorable for rapid intensification, and this is a distinct possibility, especially if 90L develops before the Yucatan Peninsula. Residents of the Yucatan Peninsula, as well as Veracruz, Northern Mexico, and even South Texas, should closely monitor the progress of 90L.  Much like 99L, the exact details on the track and intensity of 90L are highly uncertain as of this time. I give 90L a 10 percent chance of development within 48 hours, and a 60 percent chance of development within five days.

Tropical Depression Eleven-E forms over Eastern Pacific, not expected to strengthen

A tropical wave developed into Tropical Depression Eleven-E over the Eastern Pacific on Friday morning. Eleven-E is currently disorganized and heavily sheared, with the circulation center to the east of the convective mass. As of 9:00 p.m. MDT (11:00 p.m. EDT) Friday, Eleven-E was centered near Socorro Island, near 18.6°N 111.0°W, and was moving west-northwestward at about 13 mph.  Maximum sustained winds were 30 knots (35 mph), with an estimated minimum pressure of 1005 mb. The depression is not expected to strengthen into a tropical storm, and is expected to begin weakening by late tomorrow. Eleven-E is expected to degenerate into a remnant low by early Sunday as it moves into even stronger shear and a drier, more stable environment. If Eleven-E does manage to become a tropical storm, it will be named Jova.

I will be back tomorrow with another post. The next two Atlantic names are Franklin and Gert.