Three Dimensional Analysis of Dropsondes during Major Hurricane Irma to Examine Rapidly Decreasing Wind Speeds near the Surface of Dropsonde Profile

During the 2017 Atlantic Hurricane season, several Aerial Reconnaissance Weather Officers (ARWO) had difficulty capturing the maximum surface winds with dropsondes on the inbound and outbound legs during missions into Major Hurricane Irma. Dropsondes identified peak winds between 850 and 929 mb (average 490 m) then observed a rapid decrease in speed, sometimes by as much as 74 knots. Our hypothesis is that once the dropsonde reaches the surface boundary layer, it is pushed towards the center of the hurricane by the inflow, causing it to miss the maximum surface winds. The objective of this research project is to use ArcGIS as a tool to plot the vertical profile of dropsondes three dimensionally over Stepped Frequency Microwave Radiometer (SFMR) and flight level wind contours to help figure out what was happening to the dropsondes as they descend into the storm. Additionally, the current technique the ARWOs are using to determine when to release dropsondes on the inbound and outbound legs for major storms was evaluated to determine if it should be updated to account for the boundary layer inflow. A total of five fixes were examined from Irma. These fixes were selected by identifying the strongest missions, along with fixes that had inbound, center, and outbound dropsonde data available. Missions close to land were also ruled out incase land interaction had an impact on the data. Four other fixes from missions into Harvey, Nate, Otto and Joaquin were examined as comparisons in weaker storms.