At the start of the 2017 hurricane season you might remember the general prediction was tropical systems will struggle over the main development region due to dry air and at times high wind shear. However, as tropical systems take shape and move westward towards the Caribbean or U.S. coastline, the overall environment will become better for storms to strengthen. So far this has been the case this season.
New Invest 97L
With little activity in the Atlantic Basin as Tropical Storm Karl swiftly moved across the North Atlantic the media is starting to hype the next tropical system. This system has been tagged by the National Hurricane Center (NHC) as Invest 97L.
Currently Invest 97L is struggling with dry air and higher wind shear, but the system is starting out at a fairly low latitude, south of 10 degrees which generally means the system will track further west vs slowly curve to the north as it tracks westward across the Atlantic Ocean. Steered by the subtropical ridge of high pressure known as the Bermuda-Azores high, Invest 97L will arrive in the Windward Islands on Wednesday bringing locally heavy rain and gusty winds. Such locations as St. Vincent and the Grenadines, Grenada, perhaps Trinidad and Tobago could be targeted islands.
You might have noticed that the (NHC) has given this system a high chance (80%) for formation into a tropical depression over the next 5 days. And many global models are suggesting a hurricane to develop after the system crosses the Windward Islands. The next named storm will be named Matthew.
There are currently west to northwest winds aloft over the Caribbean Sea, providing some wind shear which is typically hostile to the development and intensification of tropical cyclones. But if this wind shear diminishes there are very warm waters in the Caribbean which could add to the fuel of a developing tropical system.
However, as I always try to point out, the uncertainty is high and there is virtually no skill in long range hurricane forecasts seven to ten days for invest systems like Invest 97L. There will be doom and gloom forecasts by weather models at these long range. In some cases the model run might be correct but at this point in time it’s much too early to tell what the impacts will be after the Windward Islands. Right now most modeling is trending away from U.S. impact and more to Mexico impact.
Climatology would suggest named storms entering the Caribbean during the period 9/20 – 10/10 at low latitudes such as Invest 97L often become major hurricanes, but if it makes a difference there have been 17 “M” named storms since 1950 and none have made U.S. landfall as a hurricane.
If the forecast changes and a U.S threat starts to take shape I will send more updates, but if anyone wants an update just ask.