Invest 90L is now Potential Tropical Cyclone Seven; the National Hurricane Center initiated advisories this afternoon. Meanwhile, Invest 99L is unlikely to develop in the short-term.
Potential TC 7
As of the 8pm EDT advisory Potential Tropical Cyclone Seven was located at 16.1 degrees north and 82.7 degrees west, moving west-northwest at about 12mph. Maximum sustained winds were 35mph and the minimum central pressure was 1007 millibars.
Analysis: Satellite images this evening show that Potential Tropical Cyclone Seven has a decent amount of sustained, deep convective activity, but that it was mostly to east and northeast of the center. They also show that Potential Tropical Cyclone Seven has a decent amount of vorticity or “spin,” which data from CIMSS confirms.
However, ASCAT data indicates that the center of Potential Tropical Cyclone Seven lacks west winds, and is therefore not closed, meaning it is not yet a tropical cyclone.
Chance of Development:Â Environmental conditions remain favorable (we discussed them in more detail here) for continued development of Potential Tropical Cyclone Seven, and it should become a tropical depression or Tropical Storm Franklin sometime tonight.
In their 8pm EDT tropical weather outlook the National Hurricane Center gave Potential Tropical Cyclone Seven a 90% chance of developing over both the next two to five days.
Forecast Track:Â Potential Tropical Cyclone Seven will be driven west-northwest — and then west — by a ridge of high pressure over the next three to four days, moving across the Yucatan Peninsula late tomorrow and into the Bay of Campeche on Tuesday. From there it will likely make landfall somewhere along the Mexican Gulf Coast Thursday.
Intensity Forecast:Â At this time, the official forecast from the National Hurricane Center is for Potential Tropical Cyclone Seven to become Tropical Storm Franklin tonight; some strengthening into a mid-grade 50mph tropical storm before pushing across the Yucatan Peninsula tomorrow; and for intensification into a high-end tropical storm in the Bay of Campeche on Wednesday.
However, considering the environmental conditions, it would not be surprising for Potential Tropical Cyclone Seven to exceed the National Hurricane Center’s intensity forecast and rapidly intensify into a hurricane in the Bay of Campeche Wednesday.
Invest 99L
Invest 99L is still disorganized. Satellite images this evening show that Invest 99L lacks any deep convection, and data from CIMSS also shows that the vorticity or “spin” associated with 99L is still very elongated.
Chance of Development:Â The chance of 99L developing into a tropical cyclone has gone down significantly, and development now seems unlikely – at least in the short – term.
Environmental conditions remain generally favorable for development, but 99L is not taking advantage of them for some reason; and they will turn unfavorable as 99L nears the Lesser Antilles in about two days, where there is a large band of hostile wind shear and a drier air mass.
In their 8pm EDT tropical weather outlook the National Hurricane Center gave Invest 99L a 10% chance of developing over the next two days, and a 30% chance of developing over the next five days.
Model Guidance: None of the three reliable models used for predicting tropical cyclone genesis — the GFS, UKMET, and ECMWF —  are forecasting development of 99L in their latest runs.
99L will need to be monitored near the Bahamas by the end of this week: Even though 99L is unlikely to develop in the short-term, we will continue to monitor it — as it will end up in the vicinity of the Bahamas by the end of this week — and there are indications that environmental conditions could be more conducive for it to develop then.
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