Invest 99L Takes a Hit on Thursday

Disturbance Takes a Turn for the Worse; Still Expected to Bring Heavy Rains and Gusty Winds to Hispaniola, Cuba, and South Florida

There was not only some good news for residents along the Gulf Coast and South Florida on Thursday, but also a lesson to all of us about trusting the computer models when it comes to forecasting the intensity and track of a developing system. Invest 99L lost a good deal of its punch as it neared the Bahamas on Thursday.

Thunderstorm activity associated with the disturbance that has been attracting a lot of attention during the week decreased significantly. As of 8:00 AM EDT on Friday morning, the weak area of low pressure that extends from Eastern Cuba northward into the Central Bahamas continues to have disorganized shower and thunderstorm activity according to the National Hurricane Center.

In addition to the weak convection, the disturbance also has to deal with unfavorable atmospheric conditions, particularly hostile upper level winds. The upper level wind shear is expected to persist for the next couple of days. Hurricane Hunter aircraft was supposed to fly into the area of disturbed weather on Friday morning, but the mission has been cancelled. The disturbance is moving to the West-Northwest at 10 miles per hour.

As of Friday morning, the chances of formation with the disturbance, Invest 99L, is at 10 percent over the next 48 hours, and over the next five days. So, the damage done to Invest 99L on Thursday has crippled it significantly for the time being. However, conditions could become more favorable for development at the start of next week when Invest 99L enters the Eastern Gulf of Mexico where sea surface temperature usually run high, and upper level winds are more accommodating.

Regardless of what happens with Invest 99L, residents in Eastern and Central Cuba, Hispaniola, the Bahamas, and South Florida and the Florida Keys should expect heavy rains and gusty winds starting with Eastern and Central Cuba and Hispaniola on Friday and spreading into the Bahamas, South Florida, and the Florida Keys during the course of the weekend. Heavy rains are a significant concern in Cuba and Hispaniola where the terrain is more mountainous and can produce flash floods and mudslides.

Looking at the model performance to date with Invest 99L, Bryan Norcross of The Weather Channel said it best when he said that both the Euro and GFS “suck” when it comes to forecasting developing or fledgling systems such as Invest 99L. They are much better at predicting storms that are more mature such as a major hurricane. This could be due to the fact that developing storms are more fragile when it comes to dealing with environmental conditions such as wind shear, dry air, and mountainous terrain. The models don’t quite grasp that concept.

We still need to keep an eye on Invest 99L. In the past, there have been storms such as Hurricane Frederick in 1979 or Hurricane Andrew in 1992 that were basically given up for dead, and experienced a dramatic resurgence to become a memorable, destructive, and even deadly storm. Residents along the Gulf Coast should continue to monitor the progress of this still developing situation.