S25 An Investigation of Intensification and Precipitation Associated with Land-Falling Hurricane Isaac over the Gulf Coast of United States using Remote Sensing Technology

Sunday, 6 January 2013
Exhibit Hall 3 (Austin Convention Center)
Warith I. Abdullah, Jackson State University, Jackson, MS; and R. S. Reddy and W. L. Walters

Under NASA Innovations in Climate Education (NICE) a study has been undertaken to investigate the Ocean-Atmospheric Interactions and Precipitation associated with the land-falling hurricane Isaac over the Gulf Coast of United States using Remote Sensing Technology. During August 28th – 29th 2012, Hurricane Isaac made landfall upon the Gulf States including Louisiana and Mississippi. The tropical cyclone underwent slight strengthening after remaining at Tropical Storm status while traveling through the Caribbean and Gulf of Mexico basin (GOB). During August 25-28th, analysis of GOES-EAST satellite data from the University of Wisconsin CIMSS of Deep-layer wind shear, upper level divergence and lower level convergence shows, the wind shear was 10 – 20 knots; divergence was between 20- 30 knots until increasing above center of Isaac circulation to 40 knots as it entered the GOM basin; low level convergence was between 15-20 knots until increasing to 30 knots with an intensification on August 29th with maximum sustained winds at the surface at 75 mph. Data using GISS GHCNv3 model data for August 2012 showed only slight SST anomaly of 0.2 – 0.5° C for GOM, and data from University of Rutgers Coast Ocean Observation Lab gave SST's within 29 – 29.5° C within the mid-basin of GOM and particularly south and east of the Louisiana Delta where Isaac's center of circulation drifted upon landfall. A lack of steering winds allowed enough convection strength despite moderate wind-shear, but the center of circulation moved over cooler waters near the mouth of the Mississippi river and contributed to weakening. NOAA NESDIS RAMMB provided 16 km Geostationary water vapor imagery showed little dry-air intrusion into the storm, but showed a prominent layer of dry air with zonal component within interior mid-west of U.S associated with a strong high pressure system. The high pressure system gave Isaac steering winds upon landfall. Maximum CAPE values taken from sounding stations in Slidell, LA were 665.5 J with vertical motion totals at 20.70 m/s and at Lake Charles, LA with CAPE being 853.39 J and vertical motion totals at 23.70 m/s. AMSU-B channel16 at 89 Ghz analysis showed cloud-top intensities with lowest brightness temperatures in the south-west quadrant of Isaac during August 27th 2050 UTC, representative of slight strengthening; through August 28th 2039 UTC, the most intense cloud bands were located in both southern quadrants as concentric eye wall formed during Hurricane status. The Cape and the cloud top intensities related to Isaac's near-stationary journey northward contributed to high precipitation totals. NASA TRMM analysis August 27th – September 5th observes > 200 mm in southeast Louisiana, > 280 mm southeast Mississippi and > 320 mm western Alabama. We also computed heat fluxes using buoy data from the National Buoy Data Center (NBDC) over the Gulf of Mexico during hurricane Isaac's approach towards land.
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