Debby going to be a forecast challenge

The latest computer model guidance regarding tropical storm Debby has not helped to paint a clearer picture of where the storm, forecast to be a hurricane, will eventually make landfall. In fact, this could be one of the more complicated storms to deal with in quite some time.

Currently, Debby is experiencing some shear which means the upper level winds are blowing across the top of the storm from a certain direction rather than fanning out in all directions. The shear is keeping the storm from being able to align itself vertically and the deepest convection is displaced well away from the center of circulation. This shear is forecast to relax but as mentioned in the latest NHC discussion, it is not a guarantee, so Debby may have some intensity issues over the next few days. It is important to note that intensity forecasting is where the least amount of skill lies and significant changes up or down are possible. The latest forecast maintains the notion that Debby will become a hurricane as it turns west across the warm Gulf of Mexico.

The track forecast is turning out to be quite difficult. What was once a fairly straight forward forecast that Debby would turn west under a developing ridge of high pressure has turned in to a potential huge change coming up. The NHC mentions the ECMWF model which has shown Debby moving west and even south of west towards Texas for the last several days now has the storm making landfall in Louisiana in about three days. As I mentioned, this is a big change from previous runs and we’ll have to see what happens with each subsequent run. In other words, is this the beginning of a trend of just a temporary “goof” by the model and it will get back on its “west” idea soon. We’ll have to wait and see. Track forecasting is sometimes quite easy, this time, it looks to be just opposite.

HPC 3 Day Precip Forecast

HPC 3 Day Precip Forecast

Let’s talk about rain fall. Taking a look at the HPC’s precip forecast for the next three days, we can plainly see that Debby has a tremendous amount of moisture to dump along its path. The Florida peninsula through the central Gulf Coast could receive several inches of rain as Debby moves quite slowly, allowing the rain fall totals to pile up. This is not to be taken lightly. Fresh water flooding from excessive rains generated by tropical cyclones is a leading killer. Often times flooded roads are accessed by people who think that they can navigate the waters. This is a dangerous idea and I urge people to be mindful of the potential flooding impact from the rain. I would like to point out that you can use weather.gov for a wealth of information regarding your local conditions. Just type in your ZIP Code and the landing page will likely contain all sorts of locally based watch/warning info, hurricane local statements and more. This info is for your area, not a national broad brush forecast. Remember: weather.gov

I am currently in Georgia after wrapping up a project I had with CNN to launch a weather balloon and its payload to high altitude yesterday morning. The prep and launch were spectacular, I cannot wait to show you the video of that. The ascent went very well and we were able to track the payload using APRS. I will post a separate blog about this project later tomorrow, complete with some video of the launch. I’ll also talk about what went wrong and why we were not able to recover a majority of the payload after the balloon burst.

Once I return home from GA later today, I’ll begin preparing equipment for a trip to the Gulf Coast to provide on-scene coverage and info as Debby passes by or perhaps makes a direct impact on the region. I’ll lay out my plans tomorrow as a lot will hinge on what the forecast track is and how strong Debby gets. Meanwhile, everyone along the Gulf Coast should keep close tabs on the latest forecast info from the NHC and your local NWS. I’ll have another post here tonight with frequent updates on Twitter.

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