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Decision Time on Invest 99

It’s decision time. Time for Invest 99 - the disturbance north of Puerto Rico (not Gaston) - to tell us which path it will take. How strong it will be. But is it time for Floridians to think about the “what if”?

It certainly wasn't time for the National Hurricane Center to start issuing advisories on a Tropical Storm [Hermine]. In fact, as of their 8 pm update Wednesday evening, chances of cyclone formation in the next 48 hours were reduced to 50 percent. Chances thereafter are still “high” and at 80 percent.

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Jump to: Lessons from Erika • Beware the Share • What could happen



Not Yet

Despite tropical storm force winds measured at over 45 mph, Hurricane Hunters could not find a closed center of circulation Wednesday afternoon.



Satellite data suggested a low-level center of circulation was trying to form Wednesday afternoon.


However, strong wind shear was also noted, which is why all of the thunderstorms seem to be firing well away from the supposed axis of the tropical wave.


Invest99 Setup-FPBS

It won't be until the wind shear relaxes that Invest 99 can get organized and possibly be declared a tropical depression or storm.

Lessons from Erika

There are remarkable similarities between Invest 99 and Tropical Storm Erika of 2015. First of all, it was on this date one year ago that Erika formed and a "cone" came out that had Florida in its crosshairs. However, the storm had a tendency to “underperform” when measured against the forecast data, largely because the system veered off course slightly to the south. The subtle shift in track resulted in a center of circulation that had to traverse the mountainous islands of Puerto Rico and Hispaniola. If Erika (or in this case, Hermine) were to stay just to the north of the island chain, the outcomes would have been (or could be) much different.

As we were thinking about creating graphics to show possible outcomes from Invest 99, we couldn’t help but show the one we created last year. It’s about 3:20 into this video.

Beware the Share

We’ve been a bit quiet on social media in the past 36 hours for good measure. There is no official forecast yet for Invest 99. And there won’t be until a depression or tropical storm is identified. Any image you may have seen of a hurricane hitting Florida is likely just one forecast model (out of dozens) and likely doesn’t credibly represent a potential outcome with soon-to-be Hermine.  We encourage all Floridians to remember this

What Could Happen

We’ve narrowed down potential outcomes for Invest 99 to three possible scenarios, which ironically are very similar to what we did for Tropical Storm Erika last year.


Invest99 Scenarios-FPBS

Scenario 1: Soon-to-be Tropical Storm Hermine crosses South Florida or the Florida Straits and into the eastern Gulf of Mexico as a weak tropical storm. Thereafter, it may briefly strengthen and turn north toward the Florida Panhandle.  This is the most likely scenario at this point, and supported both by the most recent runs of the GFS, Canadian and European models. The European, however, is projected a much stronger storm to form in the eastern Gulf of Mexico.


Scenario 2: It is still very plausible that Invest 99 never develops into a tropical cyclone and is unable to overcome the wind shear and dry air it is presently fighting off, all the while challenged by the high terrain of Hispaniola on a more westerly course. Recent satellite data suggest


Scenario 3: Soon-to-be Tropical Storm Hermine’s circulation develops further north and takes a trajectory more northwest toward the east coast of Florida, either brushing by or actually coming ashore. Many prior forecast models have suggested such a track, but they also had suggested Invest 99 would be on a more northward course by now. Support is waning for this idea among the reliable forecast models.


Sources include nearest National Weather Service office, National Hurricane Center, and the Florida Public Radio Emergency Network (@FloridaStorms).
Sources include nearby emergency management agencies, FEMA, and your local NPR affiliate. 
Sources include the Florida Department of Transportation, Florida Highway Patrol and other nearby traffic information.

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