Gulf hurricane talk: fact vs. fiction

A category 5 social media storm hit the internet on Tuesday compliments of a singular run of the European weather model. The run in question shows a likely tropical storm hitting south Florida over the weekend before moving into the Gulf of Mexico and strengthening into a significant hurricane.

Credit: WeatherBell / valid Mon. PM, Aug. 29, 2016

Fact: All we have right now is a poorly-organized tropical wave

The model is developing a hurricane from what stands today as only a very poorly-organized tropical wave with a broad, ill-defined circulation. The Hurricane Hunters confirmed this with a flight on Tuesday, but truthfully, satellite told us all we needed to know about the system at this point.

Fiction: We are certain that the system will develop

The National Hurricane Center is currently giving the disturbance, deemed Invest 99L, a 60% chance of development in the next 5 days. Those are relatively high odds but also represent a 4-in-10 chance that nothing happens with this through the weekend. In the short term, 99L has to fight off wind shear and some dry air. As it eventually gets closer to the Bahamas late in the week and into the weekend, conditions look as though they may be more favorable....IF it survives that long.

Fact: Tropical systems are notoriously difficult to forecast in their formative stages

Until we have an organized area of low pressure with concentrated t-storm activity, take any model projections you see online for 99L with a BIG grain of salt. Models are notoriously bad with both track and intensity in the early stages of development. Michael Lowry with The Weather Channel tweeted a great graphic from the National Hurricane Center that supports this point. 

Credit: National Hurricane Center

The graphic above is limited to systems that have at least become a tropical depression or stronger, so you can imagine with a poorly-organized tropical wave like we have now the error only grows.

Fiction: If 99L does develop, we know where it's going

Most of our forecast guidance is in agreement that 99L should be somewhere in the vicinity of the Bahamas by late this week or this weekend. But while the European model shows a strengthening tropical storm, the GFS never really develops the disturbance.

Should it develop, the European model suggests strong high pressure along the East Coast would leave 99L with little choice but to head westward toward the Gulf of Mexico. However, if we look at the European ensemble forecasts -- 51 runs of the European model with slightly different starting conditions in each run -- you see there's quite the spread on where the center of low pressure associated with 99L may actually go.

Credit: WeatherBell / valid Tues. PM, Aug. 30, 2016

In the map above, each red 'L' represents the forecast location of the low pressure center from a single ensemble member of the European model. Note that the possibilities extend all the way from the Carolinas to Mexico. When we see a map like this, it's an obvious cue that forecast confidence is fairly low at this point.

Bottom Line

Given the historic flooding we've experienced over the last couple of weeks, it is completely understandable that any talk of a tropical system in the Gulf would put us a bit on edge. And, in fact, we all should keep a close eye on 99L in the coming days.

But understand that we are in the formative stages right now and uncertainty is very high on both the future track and intensity of 99L.

In a worst case scenario, impacts to our area would be roughly a week away. However, please remember that odds of this system heading our way are still quite low at this point. Stay alert and follow us in the coming days for additional updates.