Evolving boundary layer measurements during hurricanes Gustav and Ike

During the 2008 hurricane season, hurricanes Gustav and Ike moved over the Gulf of Mexico and interacted with the Loop Current (LC) and the mesoscale eddy field. As part of the National Center for Environmental Prediction (NCEP)-directed tail Doppler Radar Missions, concurrent oceanic and atmospheric measurements were acquired from sixteen NOAA WP-3D research flights for pre-, during and post-storm conditions. Such coupled measurements are absolutely necessary to improve models at the National Centers.

Briefly, over two-hundred global positioning system (GPS) sondes were deployed during the in-storm flights across the Gulf of Mexico to document the evolving atmospheric structure over warm and cool ocean features. Each research flight deployed Airborne eXpendable BathyThermographs (AXBT) to document the evolving upper ocean thermal structure across the entire Gulf of Mexico for the first time. In support of operational modeling efforts at NCEP, more than four-hundred AXBTs were deployed on these research flights to document the coupled boundary layer responses. To complement these data, twenty-one drifters (10 with 150-m thermistor chains) and floats were deployed by the Air Force WC-130J northwest of the LC. Over this array, forty-five GPS sondes were deployed and surface winds were mapped from Stepped Frequency Microwave Radiometer (SFMR). These data are being processed to assess data quality and the levels of the observed ocean thermal response in the LC and Gulf Common Water, and to relate these data to the evolving boundary layer structural measurements.

This prototype experimental approach will be conducted during the 2010 hurricane season from research aircraft as part of the NOAA Hurricane Forecasting Intensity Program Experiment and Minerals Management Service (MMS) sponsored Dynamics of the Loop Current Study. Several MMS-sponsored moorings will be deployed for about 30 months this summer in the LC-eddy shedding area. This region is where both hurricanes Katrina and Rita rapidly deepened to category-5 status in 2005. In addition to GPS sondes and SFMR measurements, ocean measurements this summer will involve the deployment of aircraft expendable current, temperature and salinity profilers (AXCPs, AXCTDs) prior, during and subsequent to hurricane passage over the eddy shedding area and possibly drifters and floats in the warm eddy and the Gulf Common Water. These measurements will provide signals to examine the oceanic response and assess its feedback to the hurricane boundary layer and aim to improve coupled forecast models.