Two investigative areas “invests” – one over the Atlantic (Invest 99L) and one over the Eastern Pacific (92E) have a good chance to develop into tropical depressions this weekend. 99L – an area of low pressure we have been tracking in the Atlantic for over a week – is expected to move into a more conducive environment for development this weekend as wind shear is expected to decrease. Invest 92E, associated with the remnants of Atlantic Hurricane Franklin, is very likely to become a tropical depression over the Eastern Pacific during the next day or so.

99L likely to develop into a tropical depression this weekend, but dry air could limit development

A broad area of low pressure – designated Invest 99L – about 300 miles east of the Turks and Caicos Islands has a medium chance to develop into a tropical depression during the next few days. As of 00:00 UTC Saturday, Invest 99L was centered near 22.5°N 67.0°W, and was moving west-northwestward at about 10 mph. Maximum sustained winds were estimated at 25 knots (30 mph) with an estimated minimum pressure of 1012 mb. The National Hurricane Center (NHC) gives 99L a 40 percent chance of development within 48 hours, and a 60 percent chance of development  99L has changed little in organization today. Mid-level dry air has limited organization, although wind shear is falling around the system. Convective activity has recently collapsed, but could rebuild overnight as the diurnal convective maximum approaches. The 12z Friday ECMWF, UKMET and CMC model runs all supported some development of 99L by Sunday, while the 18z Friday GFS model run continued to predict very little development. 99L will most likely remain weak if it develops due to the dry air. Wind shear is expected to remain favorable, below 15 knots, for the next 48 hours or so. However, wind shear is expected to increase to over 15 knots on Sunday. Sea surface temperatures are expected to remain favorable, near 29°C (84.2°F), for the next few days. Mid-level relative humidity values are expected to remain marginal, near 50-55 percent, for the next five days, and this could limit significant development of organized thunderstorm activity.  However, if development occurs and 99L begins to acquire extratropical characteristics in four to five days, some strengthening is possible at that time due to baroclinic processes. There is a low chance that 99L develops into a hurricane, as suggested by the UKMET model, if it can mix out the dry air intrusions. Nearly all models agree that 99L will curve out to sea between the United States and Bermuda, and a United States landfall is not expected. However, if 99L develops, high surf is possible along portions of the East Coast. The next name on the Atlantic naming list is Gert.

92E (remnants of Franklin) expected to become a tropical storm tonight or tomorrow

The remnants of Hurricane Franklin emerged into the Eastern Pacific early this morning, have become better organized, and have been designated Invest 92E. As of 00:00 UTC Saturday, Invest 92E was centered near 19.1°N 109.2°W, and was moving west-northwestward at about 10-15 mph. Maximum sustained winds were 35 knots (40 mph) with an estimated minimum pressure of 1003 mb. NHC gives 92E a 90 percent chance of development within both 48 hours and five days. Since 92E already has tropical storm force winds, it will immediately be named Jova one it acquires sufficient organization to be designated a tropical cyclone. Convective activity has become better organized during the past several hours, and the low-level circulation is gradually becoming better defined. The 12z Friday ECMWF and CMC model runs, as well as the 18z Friday GFS run, develop 92E into Tropical Storm Jova by tomorrow.

Although 92E is expected to become a tropical storm, conditions are expected to become less favorable for development by early next week when 92E is expected to cross the 26°C (78.8°F) isotherm. 92E is not likely to become a hurricane, and should remain south of the Baja California Peninsula and not have a significant impact on any land areas.

Elsewhere in the tropics

In the Eastern Pacific, the NHC is also monitoring an area of disturbed weather centered a few hundred miles south-southwest of the Gulf of Tehuantepec. The NHC gives this disturbance a 30 percent chance of development within 48 hours, and a 70 percent chance within five days.

In the Atlantic, a new tropical wave expected to emerge off the African coast by early next week is worth watching. The 18z Friday GFS and 12z Friday ECMWF model runs, as well as some of their ensemble members, indicated the possibility of this wave to develop into a tropical cyclone by the middle of next week. This wave has not yet been mentioned on the NHC Tropical Weather Outlook. It is far too soon to determine where this disturbance will go, and how strong it will be, if development occurs.

Tropical Storm Banyan has formed over the Western Pacific, and is likely to strengthen into a typhoon on Sunday over the open Pacific waters. Banyan is not a threat to any land areas.

I will be back with another post tomorrow.