I study tropical climatology, hurricanes, severe weather and remote sensing of rainfall at the University of Florida. AMA!

What is it about hurricanes that makes their path and strength so difficult to predict? Why are they so inconsistent with their movement patterns?

Hurricanes are affected by the environment, and they also affect the environment around them. A stronger hurricane will interact with the environment differently than a weak hurricane. Our track forecasts have increased in accuracy over the past decades. We still find it challenging to accurately predict storm intensity. Intensity is the one minute maximum sustained windspeed and tends to be located near the storm's center in the Atlantic basin. It is a very small point that we need to model in order to make a prediction.

Could we make your lives easier by using some different measure of intensity, like mean velocity or something?

Are you asking about a different way to measure the wind, or are you talking about the overall damage potential of a storm?

We know that a limitation of the Saffir Simpson Scale is that it was constructed based on wind damage and it currently only includes categories related to the maximum sustained wind speed. This doesn't consider how far out damaging force winds extend from the storm's center, which would be a measure of the wind field's size. It doesn't give us a great estimation of storm surge heights. It does not provide any indication about rainfall potential or tornado production.

Are you asking about a different way to measure the wind, or are you talking about the overall damage potential of a storm?

More the first one; I was just imagining like seismologists get to describe earthquakes on a rigorous scale tied to the energy of an earthquake, that doesn't tell you much about how much damage it'll do, but they can get the answer out really quickly because it's specific to the dynamics of the earthquake itself.

Whereas it seems like if you have this great moving mass of wind, you probably know all kinds of things about it overall that you could report accurately quickly, before you know precisely what it's going to do when it hits land.

I'm imagining some kind of mean angular momentum or energy measure or something, so we can say "that's a big hurricane" in some natural way.

That's a great, detailed question!

Hurricane scientists calculate ACE, which is the accumulated cyclone energy. This takes into account the strength and duration of the storm; although, it doesn't take in account the size.

There is also IKE (integrated kinetic energy), and this does account for the distribution of different wind speeds around the storm.

What would you most like to tell us that no one ever asks about?

We forecast the center of the hurricane, and that's the main focus and is around the area where the fastest winds will occur. Storm surge is affected by a lot of other factors on the ground and could rise higher in a bay or inlet well away from the storm center. Tornadoes most commonly form in the outer rainbands, around 250 kilometers from the center. Rainfall can be heavy near the center in the eye wall and also in the outer rainbands producing those tornadoes.

With that, people should not focus solely on the predicted track because tornadoes and flooding can occur a couple of hundred miles away from the storm center even after landfall. People should stay alert in the days after landfall, too.

On the topic of climate change, how is the climate affecting hurricanes, tornadoes, etc?

There's an increase of energy in our climate system, and extreme weather events occur as one of the mechanisms to balance and use this excess energy. This energy could be put into increasing wind speed or raising a temperature or causing more evaporation that could lead to more clouds and precipitation, but all of these possibilities can occur at different places and different times. It's hard to point to any one event and say that it is a direct result of climate change.

What is the most interesting thing about weather related natural disasters that you would like to share with us?

On a per storm basis in the US, more people die from fresh water flooding from rainfall in tropical cyclones. Storm surge can affect a lot of people at once; however, most storms don't generate a devastating storm surge. Many tropical cyclones generate enough rainfall to at least cause localized flooding. Plus, flooding rainfall can occur hundreds of miles inland from the coast.

I have noticed multiple storm systems occurring in (relatively) the same latitude at various times during the hurricane season.

1. Is there a name for this phenomenon?
2. How do the rain shields affect each other?

1. Hurricanes can form in different parts of the Atlantic basin at different times of the season when the conditions are present like warm ocean waters, moist atmosphere, a preexisting disturbance that provides spin and where winds are relatively calm above that disturbance. Then their motion is determined by large scale circulation features that might be 1000 miles or more away from the storm and these features like the Bermuda High, themselves move, grow, shrink, strengthen and weaken throughout the hurricane season. So, there can be similar tracks taken by storms because they formed in similar regions under similar conditions when these steering forces are occurring. We actually use this to verify our forecast again with Climatology and Persistence (CLIPER). Just because they pass through a similar latitude doesn't mean there is a name for this but it's not that it's unexpected.
2. When two tropical cyclones move near each other, it is possible for one to move around the other; this is called the Fujiwhara Effect. It's not specifically related to the rain shield but the wind dynamics of the system.

Hi, Dr. Matyas – thanks for taking time to share your knowledge today. In your bio/intro you mention your two broad research goals – what sorts of breakthroughs do you hope to glean from the rain fields data? Do you envision this work impacting policy decisions, and/or enabling officials to make more accurate assessments on evacuation orders, especially when considering one topographical region to the next?

Evacuation orders are issued for places concerning storm surge. We don't issue evacuation orders for potential flash flooding for rainfall, at least not right now.

The amount of rainfall that can trigger a flood is dependent on a number of factors, including, how saturated are the soils, the land use of the area as urban environments are full of impervious materials that don't drain quickly enough, steeper slopes hold less moisture before they fail, and how much of an area upstream feeds into the area of the location where you're located; you can flooding several days after peak rainfall due to runoff upstream.

Predicting a flood and enabling people to evacuate people from that area is complicated, but the first step is to better predict the rainfall itself. One example is how does a tropical cyclone interact with the air mass over the continent as it makes landfall; how quickly does dry air spiral into the storm's center and reduce rainfall versus does moisture get uplifted over dry air to temporarily enhance rainfall. These are processes I am currently studying.

Outrageous amounts of rainfall seem to cause as much damage and concern lately as wind or storm surge, as in the stalled systems off Texas and along the eastern seaboard and the flooding in the farm belt. Why do these seemingly once-in-a-lifetime rain events catch us by surprise? Also, how exactly is remote sensing used in studying rainfall?

The heavy rainfall caused by Harvey in 2017 and more recently the rainfall over the Houston area was fairly well predicted by the Weather Prediction Center in the sense of potential record rainfall would occur. Whether the forecast was for two feet of rain and more than that actually fell, we can consider that to be an overwhelming amount of rainfall in such a small amount of time that would trigger flooding. Once the forecast goes above a certain threshold for flooding, we don't have to accurately predict the rainfall total to know that flooding is likely.

In terms of remote sensing, we have sensors aboard satellites that help detect the amount of moisture in the air, the presence of clouds, the presence of other atmospheric components like dust. Also, the radar data you might look at your phone comes from another type of remote sensing instrument where a signal is sent out from the radar antenna and the amount of signal received back tells us about the amount of water in the air, which translates to the rate of rain.

People I talk with in the US think that it’s mostly Florida that’s at risk of flooding due to climate change. But New York and New Jersey had Sandy and Boston recently had severe storm flooding. How do we convince people that most of the East Coast is at risk? It’s not just Florida.

Any coastal region is vulnerable to flooding, especially since we continue to build more infrastructure in these areas. It doesn't take a named hurricane to cause rainfall that is extreme enough to trigger a flood. We saw this summer that middle of the United States experienced weeks of flooding from heavy rainfall events that occurred day after day in the same region. One of the possible outcomes of climate change is that extreme rainfall events could become more frequent. However, we can't say precisely where or when these will occur. We may also see areas that experience a lack of rainfall in ways that they are not accustomed to. We could see either end of the extremes in different places in the US.

How do you go about building a model of a hurricane? Do you have some kind of cube by cube wind speed model, or are there kind of overall measures of storm specific variables you analyse?

When we model a hurricane, we do think about space as comprised of cubes that interact with one another. It's more complicated than just wind alone. We have to consider heat and moisture and forces that act on the wind like gravity, friction, pressure gradients, centrifugal force, coriolis force from the Earth's rotation, etc.

In a model, we cannot accurately represent all processes that occur in nature. Therefore, some of the processes have to be substituted for by using a statistical function or a more basic calculation. This is one of the reasons why we can have so many solutions from a model because we can pick different processes to simplify and that affects the prediction that the model makes. In a model environment, rain can occur without a cloud forming; you must specify both the cloud formation process and the precipitation-producing process so they both accurately work together.

My son is nine and loves severe weather. What type of opportunities or programs are available for him to learn more advanced aspects of weather science? He has already absorbed all of the books I could find.

That's great to hear your son has an interest in severe weather at such a young age. I helped participate in these science teaching resource models he may find interesting: http://fcit.usf.edu/florida/teacher/.

Hi Dr. Matyas!

Former student of yours at UF here.

First off, thank you for the two wonderful classes that I took with you in my time there. You made my fascination with severe weather even greater!

As for my question, what are some good online resources for in depth storm tracking?

I remember you using sites in class but I forgot them!

Thanks for reaching out! That is great to hear. Feel free to email me directly, and I can send you some of the resources from class.

Is storm surge/flooding the major cause for building destruction? Florida building codes are so strict post Andrew, it seems like most cement block, boarded up, highly rated roof straped houses are fairly impervious to cat 5 winds, is that true? Was the destruction we saw in the Bahamas mostly because of the storm surge?

I'm not a structural engineer, so I can't speak about in specific cases whether the wind or storm surge were the most damaging. But, water weighs more than air. For example, if you take the same volume filled with air and hit an object vs. the same volume filled with water, there will be more stress caused on the object with the water filled volume. It would be different to stand in a 10 mph wind than standing waist deep in a 10 mph flowing river.

I'm going to ask a really stupid question, but I'm interested in the science behind why.

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Why would nuking a hurricane not disrupt it? Assuming an explosion with a blast radius equal to at least the eye, if not larger, wouldn't pressure wave and subsequent vacuum serve to break the vortex, similar to the way explosives are used to deprive oil well fires of oxygen to extinguish them.

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E: NM, I didn't see someone else already asked.

Here's an in-depth answer from NOAA. It explains the mismatch in energy production. It also talks about the shockwave and the fact that less than 10% of the energy released by a hurricane is put into producing wind.

How much do solar winds affect tropical systems or weather in general?

There has been research on this, but I can't tell you about the amount specifically. I know some research has shown that hurricane intensity can be related sunspot cycles.

Is climate change real?

Human activities accelerate otherwise naturally occurring processes. It makes sense we are affecting the environment through that, however, my research does not focus on climate change.

The Florida Climate Institute, which I am a member of, shares this in regards to climate change: https://health2016.globalchange.gov/.

What are the top three ways that an individual can help to slow climate change that might ACTUALLY make a difference?

It's a collective action that led to this and only a collective action will help to improve the situation.

I've heard rumors about 5g telephone networks having adverse effects on severe weather sensing: Is there anything to that?

I'm sorry, but I'm not sure how telephone networks operate.

Do humans do anything that controls the suns temperature? And is there anything we do that will cause the ocean currents to change?

Humans cannot affect the sun's temperature.

Ocean currents do change over very long time scales, like thousands of years. Changing the salinity of the ocean by adding more freshwater can then change the rate at which water may sink or rise in certain areas.

Hello Professor, I’m interested in finding out how climate change will affect future hurricanes as the oceans warm. It’s inevitable they will be stronger, but to what extent do you think that will be? Also, will we see an increase in the number of hurricanes each year or just the strength of the hurricanes themselves? Thank you for your time!

Ocean conditions are not the only ingredient we need to form a hurricane. We also need ample moisture in the atmosphere, so if there are dry pockets within the atmosphere we wouldn't see as many storms form. We also need the winds to be relatively calm throughout the atmosphere, and if winds are fast in the upper part of the atmosphere that would not allow many storms to form. It's a more complicated issue than just ocean conditions.

The President has (unfortunately) suggested we should nuke hurricanes. Out of curiosity, what would that do to a hurricanes trajectory? Would it actually disrupt it, just make it more dangerous, what?

One explosion would not contain nearly enough energy to have a measurable affect on a hurricane. Scientists have known this for decades.