OTREC joins the hunt for a hurricane!

On Sunday August 18, 2019, I had the exciting opportunity to participate in my first ever research flight. 

Me, with the NOAA P-3 in the background after the flight

Over the weekend, OTREC collaborated with NOAA’s Hurricane Research Division (HRD) to investigate a tropical disturbance that has been identified as “Invest 95E” by the National Hurricane Center – which means that this disturbance has the potential to develop into a hurricane and is something worth investigating.  I got to fly on the NOAA P-3 airplane (NOAA-42, affectionately named “Kermit”).  This airplane is one of the famous “Hurricane Hunters”, which regularly fly into hurricanes to take in situ observations that are vital for the forecasters at the National Hurricane Center, as well as flying research missions. The picture below shows all the hurricanes that the plane has flown through – more than 100! It truly is an impressive aircraft that can withstand flying through almost any type of condition and is outfitted with a lot of specialized equipment for monitoring hurricanes.

A sticker for each hurricane that this airplane has flown through. The most recent one was Hurricane Michael (2018), which devastated the Florida Panhandle near where I live in Tallahassee, FL.

Since HRD was interested in researching the “genesis”, or formation, of a hurricane, and OTREC is about organization of convection, this was a perfect opportunity for the two teams to work together. Unlike the NCAR/NSF Gulfstream-V (G-V) aircraft that is being used in OTREC, the P-3 flies much slower (it is powered by four huge propellers) and much lower to the ground. On this flight, the P-3 flew between 10,000 and 20,000 ft and “hunted” the center and measured precipitation around the disturbance, while the G-V flew much higher, at more than 40,000 ft, to sample the environment around the disturbance. This combination provides a much more complete picture of the environment around the disturbance than a single plane could provide. Since this system might turn into a hurricane later this week, it was a very exciting opportunity to observe the convection as it organized and as a circulation formed.

Me looking official with my headset aboard the NOAA P-3. 

I arrived at NOAA’s pre-flight briefing at the early hour of 4:45 AM, and we took off at 7 AM. Our first objective was to locate the center of the circulation. Luckily, there was a recent overpass of the disturbance by “ASCAT”, which is a satellite that measures surface winds. The satellite observations gave us a good initial guess for where the center was. Throughout the flight, we released dropsondes, which measure the characteristics of the atmosphere (temperature, humidity, pressure, and winds) as they fall from the plane, and “Airborne EXpendable BathyThermographs (AXBTs)”, which measure the characteristics of the upper ocean after they fall into the ocean.  Since a warm upper ocean is important for hurricane formation, we wanted to measure those characteristics as well -- we measured sea surface temperatures of 28 degrees C (about 82 F). 

The P-3 also has many other instruments, including a tail Doppler radar (TDR). This is different from the HIAPER cloud radar on the G-V; instead of looking down to measure clouds, the P-3’s tail Doppler radar scans vertically from the back of the plane at two different angles to get an inside look at the structure of the convection. The P-3 also has a “lower fuselage radar”, mounted on the belly of the plane, that scans horizontally. It was really cool to watch the real time measurements from these radars and connect what I could see from the radar with what the clouds looked like outside my window!

Approaching a thunderstorm (left of image). Photo taken from the window of the NOAA P-3 at 9:25 AM local time (15:25 UTC) on August 18, 2019. Position 11.5 N, 94.7 W

Photo of the onboard display showing the flight track (green line), flight level winds (barbs) and image from the lower fuselage radar. We were flying around the thunderstorm indicated by the green, yellow, and orange colors in the radar image.

Getting closer to the thunderstorm, with clouds around us in all directions. Photo taken from the window of the NOAA P-3 at 9:27 AM local time (15:27 UTC) on August 18, 2019. Position 11.4 N, 94.6 W. 

Photo of the onboard display showing the returns from the tail Doppler radar. The left and right images are scans at different angles. The colored radar returns on the right side of each image show the precipitation in the thunderstorm we were flying past (ignore the values at the bottom of the images, that is the ground). The radar is located on the tail of the plane which is in the center of the image. 

The tropical disturbance was not particularly well organized while we were flying around in it. There was a weak circulation but most of the convection was displaced to the west of the center. Much of the time I saw plenty of convective clouds outside my window,

A healthy distribution of convective clouds. Photo taken from the window of the NOAA P-3 at 9:51 AM local time (15:51 UTC) on August 18, 2019. Position 10.2 N, 93.1 W.

but there were other times where it was much clearer and I could see the ocean surface!

Cirrus above, scattered trade cumulus clouds below, but lots of clear sky through which to view the ocean surface. Photo taken from the window of the NOAA P-3 at 11:50 AM local time (17:50 UTC) on August 19, 2019. Position 11.5 N, 91.8 W. 

Comparing the winds at the flight-level of the P-3 with the winds at the flight-level of the G-V (higher up) shows that the winds were blowing in different directions at the different heights. Take a look at the figure below, showing the flight paths of the P-3 at a low altitude (in yellow) and the G-V at a high altitude (in red). If you look on the left side of the graph, you can see that the winds measured by the P-3 are coming from the southwest, while the winds measured by the G-V are coming from the northeast. This indicates vertical wind shear, which makes it harder for a hurricane to form.

Flight tracks of the NCAR/NSF G-V (in red) and NOAA P-3 (in yellow) on August 18, 2019. The wind barbs indicate the flight level winds (red for the G-V, black for the P-3) The P-3 flew between 10,000 and 20,000 feet, while the G-V flew above 40,000 feet. Note that the middle diagonal section of the G-V (red) track is not the actual track there, there is missing data.

It will be interesting to see what happens in the next few days – today, the convection seems to be better organized! The National Hurricane Center predicts that it has a 80% chance of developing in the next 2 days. The data that the P-3 and G-V collected will be valuable in understanding why the system does or does not form a hurricane.

All in all, despite the very early start (I am not a morning person!) it was an incredibly exciting and fascinating day! I am very grateful to NOAA/HRD for letting me tag along on their flight, and to the OTREC team for letting me participate in the field campaign. Below are my two favorite photos from the flight. 

Mostly clear skies just off the coast of Costa Rica, shortly after takeoff. Some scattered shallow cumulus clouds, cirrus overhead, and a developing thunderstorm (left of image). Photo taken from the window of the NOAA P-3 at 7:17 AM local (13:17 UTC) on August 18, 2019. Position 10.9 N, 86.2 W.

A thunderstorm with overshooting convection above the spreading anvil, with thick clouds at flight level (10,000 ft) and cirrus overhead. Photo taken from the window of the NOAA P-3 at 8:12 AM local (14:12 UTC) on August 18, 2019. Position 12.0 N, 90.4 W.