We Love Weather Exclusive

Post-Irma Q&A With Our Experts

Over the course of Hurricane Irma, we received several questions regarding all aspects of the storm. Hurricane experts Dr. Erika Navarro and Dr. Rick Knabb have the answers.


Dr. Erika Navarro

Why can’t we just change the scale to include a category 6, and maybe even a 7? – Jared J.

The Saffir-Simpson scale is designed to measure the potential damage by a hurricane. Since a Category 5 storm already exhibits catastrophic damage, there is no need for a higher category.  

Is it possible for 2 hurricanes to combine into 1 superstorm, or would they tear each other apart? – James L.

It is possible for two hurricanes to combine during a process called the “Fujiwhara effect.” When two cyclones are close enough together, they will begin to rotate around each other as their wind fields interact. Often, one storm will ingest the other, and only one storm will remain.   

Has any meteorologist or scientist ever been able to see what’s going on beneath the surface of the ocean within the eye of the hurricane? Is there a submarine or a water vessel that is able to penetrate the center of a hurricane below the surface of the water? – Travis B.

Scientists often use satellite and ocean observations from buoys to infer details about the surface of the ocean. The ocean heat content, or the energy stored underneath the surface of the ocean, for example, can be inferred from surface measurements.  Oceanographic instruments can also be deployed from aircraft, which activate when reaching the ocean surface and relay information back to the aircraft.

Did the tides affect the storm surge of the hurricane on one side of Florida more than another as far as the storm? Since the oceans and Gulf of Mexico have a big slosh factor, does the rising and falling of the tides at all affect the actual track of a hurricane? – Kim S.

The tides do not affect the track of the hurricane, but they have huge impacts for the storm surge. The flooding in Charleston, SC occurred during high hide, but the catastrophic flooding in Jacksonville, FL actually occurred during low tide. The maximum storm surge is exhibited when the onshore winds coincide with the high tide.  

Why do hurricanes curve Northeast when they seem to spin counterclockwise? – Jim M.

Hurricanes are steered by the mid- to upper-level environmental flow. Often, storms that approach the US east coast are driven out to sea by strong westerly winds associated with the jet stream. However, a strong ridge of high pressure over the eastern Atlantic (and the lack of a strong jet stream dip on the US east coast) can drive storms into the Caribbean of the Gulf of Mexico.  

Besides the obvious, what is the difference between a hurricane and tornado? Could one say that a tornado is basically a scaled down version of a hurricane or are they just too different to be able to compare? – Chris W.

Hurricanes and tornadoes form by very different internal processes, and differ in terms of their scale. Hurricanes are hundreds of miles across, while tornadoes at their largest can be a mile across. Despite their differences, the wind damage caused by a hurricane can be compared to that of tornado.

Why do hurricanes move so slow, and why do supercells end up moving so quickly? In fact, how do they move at all? Is it the fronts? – James M.

Hurricanes are driven by the mid- and upper-level steering, which is weaker in the tropics. Supercells are driven by vertical wind shear in the strong westerly winds associated with the jet stream.  


Dr. Rick Knabb

How does Hurricane Irma compare to Hurricane Hugo in 1989? – Joseph E.

Both were at category 4 intensity at initial U.S. landfall and both inflicted tremendous storm surge and wind damage.  They took very different tracks, however, with Irma making landfall in Florida going much farther south and west than Hugo than made landfall in South Carolina.  However, Irma still caused some water impacts in South Carolina due to both heavy rainfall and some storm surge associated with the outermost bands when Irma had weakened to a tropical storm.

I was wondering if massive wildfires affect low and high pressure in areas and if so how might these effects impacted Hurricane Irma? – Jeremy M.

The wildfires did not have enough impact on the high and low pressure systems that steered Irma, but they can have more local pressure and wind effects in the region in which they occur.

Why is it that hurricane Harvey stopped over Houston for so long but Hurricane Irma hit Florida and kept moving upward? – Erica B.

Harvey was blocked from continuing to move north, after initial landfall in Texas, by a ridge of high pressure over the central United States that persisted for several days.  Irma, however, was steered north and steadily moved over Florida in between a ridge of high pressure over the Atlantic and a low over the Gulf of Mexico and southern U.S.  Right now, Hurricane Jose currently over the western Atlantic between Bermuda and Puerto Rico is being blocked from moving north by high pressure to its north.  Good thing that slow motion is happening over the ocean instead of behaving like Harvey over land!

Why did Irma turn north so sharply? What was the driving force behind that turn? – Kaleb B.

Irma turned north when it reached the western edge of the ridge of high pressure over the western Atlantic, and moved north in between that ridge and a low over the Gulf of Mexico and southern U.S.

Please explain the “mb” number for a hurricane. Is it more severe if that number is lower or higher? – Cindy Sager

Pressure in the atmosphere – essentially depending on the total weight of air above the surface of the ocean or ground – is measured in millibars, with the abbreviation being “mb”.  The lower the pressure inside a hurricane, the greater the difference in pressure between the inside and outside of the hurricane, and therefore the stronger the winds that are swirling around the hurricane, because winds blow as a result of pressure differences as the atmosphere tries to fill in the low pressure with air of higher pressure – kind of like a rock rolling down a hill.

What does a major hurricane do to special environments like the everglades? – John Aston

Major hurricanes like Irma that pass near or over South Florida cause storm surge, pushing the salt water from the Gulf of Mexico and fresh water from Florida Bay into portions of the Everglades.  This contributes temporarily to an even greater mix of salt water and fresh water that already exists in the area, but there could be longer-term effects of Irma on the Everglades, but it is too soon to know the severity.

How much does the wind speed decrease at different distances from the eye of a hurricane? – David Doerges

The maximum winds in a hurricane are usually present in the eyewall, a solid ring of wind and rain anywhere from just a few to tens of miles from the exact center of the eye.  Outside of that “radius of maximum winds” or “RMW”, hurricane-force winds can extend up to about another 100 miles or so in large hurricanes, and winds of tropical storm force can extend up to a few hundred miles more from the center, like they did in Irma when it was over Florida and, while having weakened, became larger.


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13 Comments


  1. I certainly think a Category 6 is not plausible because the sustained winds of a hurricane, at its peak, according to the scale, is 150+ mph, allowing for winds 185 mph, like in Irma.

  2. We live a couple hours north of where Irma made landfall in Pinellas County, FL. We’re keeping the folks in our prayers who lived in the areas that received a direct hit. But folks need to understand that millions more were severely affected too. In our county over 416,000 of the 454,000 electric customers were knocked out of power. There is major tree damage and lots of house damage as well. We were without power almost a week. So there were all sorts of medical emergencies as well. But since we didn’t get a direct hit, help has been long in coming. There weren’t help stations set up, the Red Cross wasn’t here with hot meals, we didn’t even have anywhere to go to charge our cell phones. It was several days before gasoline shipments started back. Then Home Depot and some grocery stores were opened up, but with hardly any needed supplies inside. We still don’t even have much food in our stores. It’s the worst thing we have ever lived thru and yet it doesn’t “officially” count as anything. How is that??

    1. I know how you feel. I live in East Pasco county. I had to evacuate because like many seniors in our area, I live in a park model trailer and so does my son. We both went to my daughter’s house. Her electric went out Saturday about 9 PM. She didn’t get power back until Trursday. They were lucky that they had a generator so they could run refrigerator and microwave allowing them to save their food and be able to cook. I was lucky. No loss of power. I live 2 miles away. However, my park did have some damage. The roof of our laundry was completely lost. I personally have some leaks and minor damage Compared to others I feel lucky and grateful. My family goes back many generations in Florida and I remember my parents preparing for hurricanes. I’m almost 74 and instead of buying bottled water, we filled every container we could find for drinking water. We filled the bathtub for bathing and flushing the toilet. We had canned goods and my dad would make a “campfire” to use for cooking. For light we had candles and kerosene lanterns. Things have changed

    2. I know how you feel. I live in East Pasco county. I had to evacuate because like many seniors in our area, I live in a park model trailer and so does my son. We both went to my daughter’s house. I had to board my cat because my son-in-law is very allergic to cats. Her electric went out Saturday about 9 PM. She didn’t get power back until Trursday. They were lucky that they had a generator so they could run refrigerator and microwave allowing them to save their food and be able to cook. But they didn’t have any electric. My granddaughter and great grandaught both have asmutha and need the a.c.. I was lucky. No loss of power. I live 2 miles away. However, my park did have some damage. The roof of our laundry building was completely lost. I personally have some leaks and minor damage. Compared to others I feel lucky and grateful. My family goes back many generations in Florida and I remember my parents preparing for hurricanes. I’m almost 74 and instead of buying bottled water, we filled every container we could find for drinking water. We filled the bathtub for bathing and flushing the toilet. We had canned goods and my dad would make a “campfire” to use for cooking. For light we had candles and kerosene lanterns. Hurricane Donna put a large tree limb through our roof in 1960. We did not have any cell phones, tablets or computers. Things have changed

  3. When was the last cat 5 US landfall? co2 a detriment to forming high-end hurricanes?

  4. What was Irma’s miles from East to West and North to South?
    What was the highest wind gust reported and exactly where did that occur?
    What was her circumference?

  5. What keeps the planes safe when they enter into the hurricane? Those winds knock houses over! I am sure experience has a lot to do with it but there has to be something more to it. Is it about being airborne?

    1. Dr. Navarro addressed that in response to one of the questions–she basically said that category 5 is pretty much complete destruction, so you can’t really have a category beyond complete destruction.

  6. When will you begin to talk about these storms in relation to global warming, which has obviously affected the sea temperature?

  7. Did hurricane Irma underwent through an eye transformation? Also, how did Irma create a sea-sucking event in Long Island, Bahamas and Tampa, FL areas?

    1. I believe Hurricane Irma underwant several eyewall replacements–I think there were several occasions, on different days, that Dr. Postel mentioned in his broadcast that the storm was undergoing an eyewall replacement. The water in Tampa Bay temporarily got blown out of the bay by persistent offshore winds. I imagine the same phenomenon occurred in the Bahamas, although I never heard about it.

  8. I am wondering why the NHC insisted that the hurricane was going to hit the Miami-Dade area and then at the last minute it became obvious that the hurricane shifted North West and struck the Florida Keys.