Tropical Update: August 15th, 2017

The tropics are currently very active, with Hurricane Gert intensifying between the East Coast and Bermuda as it heads out to sea, and three areas of interest that have the potential to develop over the coming days: Invest 91L and 92L over the Eastern Atlantic and a tropical wave about to emerge off of Africa and into the Eastern Atlantic.

Hurricane Gert

Gert has intensified today, and is still intensifying this evening.

As of the advisory Gert was located about midway between the East Coast and Bermuda moving northeast at 15mph, had winds of 85mph, and a minimum central pressure of 979 millibars.

Latest forecast track for Gert as of 10pm EDT August 15, 2017.

Gert is expected to continue to intensify, and is forecast by the National Hurricane Center to become a category two hurricane tomorrow. However, Gert will take a path out to sea, posing no threat to the United States.

Invest 91L

Satellite images this evening show that Invest 91L, located between Africa and the Lesser Antilles, has some evident vorticity or “spin,” which is confirmed by data from CIMSS. However, the satellite images also show that convective activity associated with 91L is limited.

Chance of Development: Invest 91L still has a decent chance of developing over the next few days,  as environmental conditions are expected to remain generally conducive for development through at least Thursday or Friday.

However,  after that time upper-level winds (wind shear) and trade winds could increase when 91L reaches the Eastern Caribbean, meaning development would become less likely — if not unlikely.

In its 8pm EDT  tropical weather outlook, the National Hurricane Center gave 91L a 30% chance of developing over the next two days and a 40% chance of developing over the next five days.

Model Guidance: All three of the reliable global models used for predicting tropical cyclone genesis (the ECMWF, GFS, and UKMET) were forecasting development of 91L before it moves into the Eastern Caribbean in their 12z runs, along with many of the ECMWF and GFS ensemble members.

Latest track guidance for Invest 91L as of 00:00 UTC August 16, 2017.

Forecast Track and intensity: Invest 91L will track generally westward, along the southern periphery of a ridge of high pressure,  towards the Lesser Antilles and Eastern Caribbean over the next five days. It is too early to determine the potential track of Invest 91L beyond the next five days, or how strong it would become if it develops.

Invest 92L

Satellite images show this evening show that Invest 92L, currently located west-southwest of the Cabo Verde Islands, has a modest amount of deep convective activity, and also show that it has some pronounced “spin,” which is confirmed by data from CIMSS.

IR satellite image of Invest 92L as of 02:45 UTC August 16, 2017.

Chance of Development: Just as with Invest 91L,  Invest 92L has a decent chance of developing over the next few days.  Environmental conditions are expected to remain generally conducive for development through at least Thursday or Friday, but become less conducive by this upcoming weekend, possibly inhibiting development if 92L fails to develop before by Friday.

In its 8pm EDT  tropical weather outlook, the National Hurricane Center gave 92L a 20% chance of developing over the next two days and a 40% chance of developing over the next five days.

Model Guidance: Of the three reliable global models used for predicting tropical cyclone genesis (the ECMWF, GFS, and UKMET) only the GFS and UKMET were forecasting development of 92L in their latest runs, along with many of the GFS ensemble members.

Forecast Track and Intensity: Invest 92L will track generally west to west-northwest over the next few days, towards the Northern Lesser Antilles. It is too early to determine the potential track of Invest 92L beyond the next five days, or how strong it would become if it develops

African Wave

A new tropical wave currently over West Africa will have the potential for development when it emerges into the East Atlantic.

Environmental conditions appear to be generally conducive for some development of this wave through at least this weekend; and all of the reliable global models used for predicting tropical cyclone genesis — the ECMWF, GFS, and UKMET — were forecasting development of this wave in their latest runs.

At this time, it is too early to determine where this wave will track after it emerges, or how strong it might become if it develops.

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