Science: Hurricanes

Christopher Lee
Washington Post Staff Writer
Monday, October 8, 2007 11:00 AM

Washington Post staff writer Christopher Lee was online Monday, Oct. 8 at 11 a.m. ET to discuss efforts to learn more about how hurricanes behave.

He was joined by Joseph Cione, a hurricane researcher with the National Oceanic and Atmospheric Administration and the lead scientist on a U.S. government project that aims to send an unmanned aerial drone with weather-watching equipment deep into a hurricane.

A transcript follows.


Christopher Lee: Hi everyone, welcome to the science chat. We've been pretty lucky so far this hurricane season. No major storms have slammed into the U.S. coast, wreaking their usual havoc and destruction. As anyone who saw the Hurricane Katrina aftermath on television knows, these are storms you don't want to mess with. Unless you're a hurricane researcher, of course. We've got one with us today. He's Joe Cione, a hurricane researcher at the National Oceanic and Atmospheric Administration and the lead scientist on a government project whose goal is to send a 28-pound unmanned aerial drone into a hurricane for the first time. The idea is to take more extensive and better readings of wind speed, pressure and a host of other things that can help forecasters better understand how strong a storm is likely to become, and therefore how dangerous it will be. Joe and his team sent one of these things into Tropical Storm Ophelia two years ago, with good results. All they need now is a big storm this hurricane season to try a mission into the most powerful kind of storm. Who knows, we may get one -- the hurricane season is still very much with us. Joe's graciously given his time to answer your questions. Let's begin.


Washington, D.C.: Why do the cycles of the eye wall lead to strength fluctuations in major hurricanes?

Joseph Cione: Great question. As you have correctly stated, eyewall cycles lead to fluctuations in storm intensity. More specifically, the storm weakens when an eyewall replacement pattern develops. During this stage of the storm's lifecycle, two peaks in the horizontal wind profile occur at the same time. Normally the storms winds increase exponentially as you progress radially towards the storm center. When the storm is undergoing eyewall replacement, two wind maxima (not one) exist. Over time the stronger inner eyewall winds begin to decrease as the outer secondary wind maxima -initially weaker- begin to strengthen and 'choke off' the strong winds in the eyewall. During this period of eyewall replacement the storm temporarily weakens. After replacement is complete, sometimes the storm is stronger, sometimes weaker. Many variables go into the overall process.

Now, exactly why and the reasoning behind the exact timing of eyewall replacement is still not well understood. Further research is needed. UAS are particularly well suited to to helping in this regard since typical UAS flights can last up to 18h and help better capture the intensity change process. In comparison, most manned flights into hurricanes last 7-9h.


Miami: Can the drone help us to know how many hurricanes we will have in a year?

Joseph Cione: No. The drones (in this case the low-flying Aerosonde) won't help us with regard to seasonal hurricane frequency. They can however can give us a *better* estimate of storm intensity since they fly continuously (vs other low level hurricane observations -dropsondes,remote sensors- that give us instantaneous, "snapshot" glimpses into the storm )

Another big impact the drones could have include improving our (not so great) understanding of the near -surface hurricane atmospheric and oceanic 'boundary layer' environments. With this sort of improved understanding we will hopefully improve *future forecasts* of hurricane intensity change.


Fairfax, Va.: What do the drones cost?

Do they come back and get used again or do they perish in the storm after one use?

Joseph Cione: The unmanned aircraft (generally known as Unmanned Aircraft Systems -UAS-) are designed to return to station after the mission. They are not expendable, per say. However, at some point, we will likely lose a platform if we continue to operate these missions in the future. Our contingency plan takes this into consideration. As for cost, it depends on how the specific UAS is set up with regard to payload and sensors. Generally, cost is less than 100K (oftentimes considerably less).


Munich, Germany: I've read that the strength of hurricanes has been attributed to surface temperature of the oceans. Is there a possibility that the range of hurricanes can increase northwards if ocean warming trends continue?

Joseph Cione: Good question. Unfortunately thats an unknown right now. Certainly if/when sea temperatures increase globally, ocean ocean temperatures to the north will also rise. This could make conditions more'conducive' for future storm development. One thing to keep in mind, however. Storm formation and maintenance require more than warm ocean temperatures. Wind patterns (shear)and large scale atmospheric moisture conditions also need to be just right. It takes a lot to 'make' a hurricane, but not much to disrupt one! :-)


Washington, D.C.: How accurately can you predict the severity of a hurricane? Also, what do you attribute to the increase in them over the past few years (the last two not withstanding)?

Joseph Cione: We are limited by our ability to actually find/measure the strongest winds in the storm. This is not a trivial problem. while the strongest winds occur at low levels in the hurricane they can still occur at any region within those low levels. Unless we measure every inch of the storm (we don't/can't!) we will likely 'miss' the absolute maximum intensity (i.e. severity)of the storm. This is where the Aerosonde UAS can really help. As I mentioned in a previous question, the fact that low flying UAS constantly measure conditions within the lowest layers of the storm (where the max winds are) we have a much better chance of more accurately diagnosing just how strong the hurricane is.

Also, we are limited by the sensor's ability to measure winds. On average, current (in situ) wind speeds are accurate within 5kts (2.5m/s) or so...


Seattle: So, what is the outlook like for the rest of the hurricane season?

Joseph Cione: Our outlook (NOAA/NASA Hurricane Unmanned Aerosonde team) haven't thrown in the towel yet. Our season runs through 31 October. We are currently monitoring a developing system in the western Caribbean. If it intensifies and moves northward into the Gulf of Mexico we will likely attempt a UAS mission.


Washington DC: Don't these "hurricane hunter" airplanes already fly into the storms? Why are these unmanned aircraft better than the manned ones?

Joseph Cione: First off I do not believe unmanned aircraft are better or worse than manned aircraft. In my opinion our nation needs BOTH unmanned and manned aircraft wen it comes to observing dangerous hurricanes that potentially threaten our coastlines.

Low-flying UAS like the Aerosonde are important because they fly into regions of the storm that manned aircraft cannot due to the severe safety risks involved. It is important to sample this low level region for 2 reasons:

1. The strongest winds are down low (often less than 1000ft/300m). UAS can sample this region much more completely than what the manned aircraft are able to do. Manned aircraft observations of this region rely on remote "snapshots" and instantaneous in-situ measurements. If we want to maximize our chances of diagnosing just how strong the storm is UAS need to be part of the observational mix.

2. Due to the difficulty of observing at low levels, some of the science needed to better understand these storms is not well understood. By using UAS we will improve our knowledge of this region which will hopefully lead to improvements in numerical models that predict hurricane intensity change. It is our hope that improvements gleaned from UAS surveillance will ultimately lead to improved future forecasts of hurricane intensity change.

I should also mention that we (NOAA and NASA)have plans to use HIGH flying UAS in the coming years for hurricane reconnaissance. These unmanned vehicles will be used to fly around (and possibly over) hurricanes. Like the Aerosonde UAS these platforms will hopefully lead to improved future forecasts of hurricane track and intensity change. This can be another topic for another day! :-)


Washington D.C.: I don't understand why these drones don't get smashed to bits by the hurricane's winds? Hurricanes tear off roofs and blow over billboards and cause all kinds of other problems. How can this little airplane survive? Have you ever lost one at sea?

Joseph Cione:,So far (knock on composite materials) we have yet to lose an aircraft. This season we are running a field experiment using these UAS. In fact we are calling it a 'Demo' since we still have many questions. One of which is 'surviability'. Right now we are one for one (batting a thousand) with our successful 2005 launch and recovery into tropical storm Ophelia. The Taiwanese launched an Aerosonde into a 120kt (60m/s) super typhoon in 2005 as well. it survived in the storm. They did however fly at much higher altitudes (10000ft/3200m).

Time will tell. One last thought. Given the multi-billions in damage that strong land-falling hurricanes often leave behind, we still feel that even if we lose more aircraft than we like its still very much worth it from a cost benefit standpoint (assuming we still get the data transmitted prior to failure).


Miami: If we had a fleet of drones, could we drop enough stuff in the ocean to change the heat content so we don't have cat 5's anymore?

Joseph Cione: "Change the heat content". Mmm...

By the way, what does the word 'content' add here?

As for your weather modification question, you'd need millions of UAS since our payload is currently about 2lbs. ;-)


Well I have just been informed, that my time is up.

Thanks for all the great questions (and keep an eye out for our next flight)!


Christopher Lee: Ok, we're going to have to bring this chat to a close now. Thanks again to Joe Cione of NOAA for sharing his time and knowledge about hurricanes with us today. For those who don't know, it's a federal holiday, which means Joe did this chat on his time off. Thanks to everyone for writing in. Keep your eyes on the skies -- it will be weeks before hurricane season ends.


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