Debby exiting Florida but leaving behind a lot of water

I know that folks in Florida will be glad to see Debby moving on off the coast and out in to the Atlantic. The storm dumped anywhere from 12 to 20+ inches of rain across portions of Florida. Freshwater flooding will be an ongoing concern as rivers fill with the run off and swell to flood stage and beyond. You can check the progress of the flooding situation by utilizing the fantastic resources of the Southeast River Forecast Center. Click here to access their site. It will give you specific river flooding info for your area and provide daily updates to that data.

Debby is certainly a lesson in understanding all of the effects of a tropical cyclone. I hope that people realize that we’re not just worried about the impacts from big, mean hurricanes. Even a moderate tropical storm, even a depression, can dump excessive amounts of rain on an area and cause significant flooding issues.

Once Debby leaves Florida behind, it will move out in to the Atlantic and likely regain some of its strength over the warm waters. However, it will move away from the Southeast and not be a problem any longer.

The remainder of the tropics are mostly quiet although there is a well developed tropical wave moving westward across the open tropical Atlantic. The NHC tagged it last night as “low probability for development”. This area is not usually favorable for development in June so the fact that we are seeing some potential is interesting. I’ll keep an eye on the system as it moves westward. It is likely going to bring some rain and squally weather to portions of the Lesser Antilles in a few days but should remain only a tropical wave and not develop much.

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Debby another lesson in understanding tropical cyclone hazards

Even as Debby continues to dump rain across portions of northern Florida today, there is a lesson to be learned from the event. That lesson is to understand that tropical storms and hurricanes have multiple weapons that can cause problems. It’s not just the big headline making wind and surge machines such as Katrina, Ike or Camille. Even a weak tropical storm, like Debby is now, can create huge disruptions in the lives of those who are in the path.

Let’s take a look back at TS Allison in 2001. It formed in June and moved up out of the western Gulf of Mexico and settled in over Houston, Texas. The result was around $5 billion in damage due to the 40+ inches of rain that fell across the region. Allison is the only tropical storm to have its name retired from the 6 year list of names. Yet, for Allison, there was no mass evacuation like we saw ahead of category 5 Rita in 2005 or category 2 Ike in 2008. People usually do not flee a 60 mph tropical storm. Instead, the millions of people who live in and around Houston were treated to days of torturous rain and flooding. It was an epic nightmare and one that will never be forgotten.

Tropical cyclones produce heavy rain as a means to disperse the heat that builds up in the tropics. It’s that simple. As I mentioned in a previous post, that rain is a function of the storm’s heat engine doing its thing. It’s just unfortunate that us humans happen to live where these rains can pose serious issues for us.

Debby has dumped in excess of 20 inches of rain over parts of the Florida Panhandle. Sink holes are opening up, parts of I-10 are closed due to flooding and life for many people is simply miserable today. Yet, this was no hurricane. It did not have the “scary” 130 mph winds that would get a lot of attention. It did not push a 20 foot storm surge towards the coast. Yet what Debby has done still managed to cause a lot of grief for a lot of people. There’s no avoiding it, you can’t move your house out of the way of the relentless rain. Evacuating is only necessary if flood waters get too high. So what can be done?

My point is that people all along the coast and then a couple of hundred miles inland need to realize that tropical cyclones are more than just wind and surge producers. First and foremost they are rain makers. Too much water in too little time always equals problems. And, as we have seen time and again, too much rain over a long period of time is just as bad. So as we progress through the hurricane season, remember that all tropical cyclones are capable of inflicting damage and causing loss of life. The degree to which the various effects manifest themselves depends on many variables. This is why it is important to not focus on the hype of “a hurricane might be coming” but rather think of it as “there is a dangerous weather event that could possibly¬† change my life forever”. Then, prepare accordingly.

As for the future of Debby? It should cross Florida in the coming days and finally move faster out in to the open waters of the Atlantic. Let’s hope it does as Debby has more than left its mark on Florida.

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Good news and not so good news concerning Debby

I have some good news to share tonight about Debby. I also have some not so good news. First, the good….

TS Debby

TS Debby

The deep convection with Debby is really falling off. This means that the strong showers and thunderstorms that drive the heat engine are not functioning too well. You can easily see the void of deep convection in the graphic. The green circle indicates the area where the center is located. Without deep thunderstorm activity near the center, a tropical cyclone cannot thrive. This is important because it means that the storm is not strengthening and may be on a weakening trend. Now I cannot possibly know for sure, but seeing the collapse of the deep convection that was definitely there last night and for a good deal of today is a good sign. Perhaps the GFS’ idea of a sheared, weaker, pulsing convection type storm is really what will pan out. The ECMWF forecast of a deeper, stronger system seems to be fading quickly.

NE Gulf Heat Content Map

NE Gulf Heat Content Map

The other issue is heat content. Hurricanes get their energy from the latent heat which is stored in vast quantities in the worlds’ oceans. The deeper the warm water (about 80 degrees F) extends, the more heat content (also called upper ocean heat content) is available. Shallower water tends to hold less heat content and the shallow shelf waters off the eastern parts of the Florida panhandle are notorious hurricane killers due to this lack of energy (see the graphic to the right- the deep blue is low ocean heat content region). I think that the slow movement of Debby is helping to churn up this shallower water, exhausting what little heat content there is; further diminishing Debby’s ability to maintain deep convection.

All of this adds up to the prospect of Debby weakening and not having much of a chance of recovering. This would keep the wind and surge issues to a minimum but the rain is another problem. This is the not so good news part.

Tropical cyclones = rain. That is how they release the heat stored in the oceans. Condensation is a warming process and the release of all that rain also releases heat. This is the very nature of what makes a tropical cyclone tick, so to speak. Unfortunately, too much rain will lead to problems and it looks like the potential exists for a lot of rain for portions of the Florida panhandle and the peninsula. There is no way to know how much rain will fall and where. This all depends on the convection that I mentioned earlier. If rain bands develop, they will drop heavy rain. But those bands can fall apart very quickly too. So the timing and areal coverage of the rain is difficult to forecast. This is why it is important to keep up with what Debby is doing several times per day. The storm is dynamic, it changes. You need to use more than a few resources to keep up with what’s going on. Whether it’s the NWS site (weather.gov) or a commercial outfit such as your local TV station or other website (like us), you will want to know what the rainfall situation is even between the major advisories issued by the NHC. One great resource is the HPC site linked here where you can get detailed precipitation forecasts. The bottom line is that you need to be aware of the fairly quick changes that Debby could bring your specific area. There are numerous ways to do that.

I’ll have more updates throughout the day tomorrow. And for our Client Services subscribers, do not forget, we have a LIVE broadcast each weekday at 2pm ET where I go over detailed graphics LIVE. We also have exclusive use of Stormpulse maps, live chat and other great features that allow you to gain even more info that can help you stay informed.

 

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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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