Analysis of data gathered during NOAA WP-3D penetrations of Hurricanes Felix, Katrina and Ivan during episodes of extreme intensity

The eyewall of a Category Five hurricane is a truly unique setting seen nowhere else in the atmosphere. Being able to model the thermodynamic and dynamic forces (their conversion from one energy form to the other as well as their degree of synergy) that come into play when barotropic processes achieve these rare levels of hyperefficiency would go a long way to better understanding such storms and being able to predict rapid intensification events that lead to their formation. Research flights of the heavily instrumented NOAA Aircraft Operations Center (AOC) WP-3D into such an environment provides the best opportunity for in situ sampling of these events. The ground truth data collected by these flights is essential to efforts at creating fine scale model depictions of the core region.

The kinematics of the convective inner structure is captured by the WP-3D Tail Doppler Radar (TDR) as well as by flight level measurements of vertical winds made possible by an array of finely calibrated probes that sense air motion across the plane in three dimensions. Latest generation inertial motion sensors allow horizontal vector winds to be measured to 40 Hz resolution. This allows for the highly accurate detection of convective scale gusts. Introduction of the Stepped Frequency Microwave Radiometer (SFMR), an instrument developed over the past two decades through the teamwork of AOC engineers and scientists at the NOAA Hurricane Research Division (HRD), provides a means of dependable remote sensing of even the most extreme wind speeds blowing across the ocean surface below. Multiple temperature and humidity sensors mounted to the aircraft, as well as passive radiometers, in combination with the AVAPS dropsonde system and the ability to launch dozens of AXBTs in a single mission provides the capability to fully capture the thermodynamic structure at flight level and at the surface, as well as the intervening layers between. Of equal importance to the hardware described above, are the teams of scientists embarked aboard these flights. The expertise of personnel from HRD, NESDIS and other research organizations and universities, in working with the AOC Flight Directors during the mission, ensures that the best effort is made at capturing the most valuable research data.

This presentation will show examples of the data sets described above gathered during research missions into Category Five Atlantic Basin Hurricanes Ivan (2004), Katrina (2005) and Felix (2007). NOAA WP-3D flights into these storms during the height of their intensity, as well as (perhaps even more importantly) during their intensification phase on the way to maximum strength, yielded a wealth of fascinating data. One of the more intriguing examples includes the 163 knot SFMR measurement of surface winds during the evening of September 2, 2007 in Felix. It was during this 700 millibar eyewall penetration that the aircraft experienced extreme turbulence and very heavy graupel along with significant lightning. The dropsonde and flight level data associated with this penetration will be examined, including accompanying TDR products. We will look at a similar flight into Ivan late in the day on September 11, 2004 (during its last of three episodes of intensification to Category Five status over a four day period). Finally, two flights into Katrina, one during rapid intensification on Saturday August 27, 2005, and the next on the following Sunday afternoon flown during its period of lowest MSLP (902 millibars) will be discussed.