Doppler radar quick-looks from 4 AM P-3 flight into TS Isaac, 28 August 2012

As Tropical Storm Isaac approached landfall in Louisiana near the Mississippi Delta (outlined in black in the top left of the images)  NOAA P-3 missions collected airborne Doppler radar data to use in initializing and evaluating model guidance. Included here you see images of the horizontal winds within the inner core of Tropical Storm Isaac sampled from the tail Doppler radar on the P-3 early on 28 August 2012. These images are at three altitudes, 1 km, 3 km, and 6 km, using a composite of winds from four legs oriented north-south, east-west, southwest-northeast, and northwest-southeast. Also plotted on the 1-km altitude analysis are the locations of dropsondes deployed (plotted using standard station symbols). Isaac’s circulation is much more organized than in the previous mission, with a clear circulation center at all altitudes shown, but still asymmetric with the strongest winds north and east of the circulation center. This asymmetry increases with increasing altitude, and it is very pronounced at altitudes >6 km. The strongest winds at 1 and 3-km altitude are above hurricane force, however the surface winds from the Stepped-Frequency Microwave Radiometer (SFMR) and dropwindsondes suggested the hurricane force winds were not reaching the surface until very late in the mission. Hence, NHC did not name Isaac a hurricane until right after the P-3 left the storm. The circulation center is only slightly tilted from south to north with increasing altitude from 1-km altitude to 6-km, much less so than the previous missions. However, the increasing asymmetry with increasing altitude suggests that the southerly shear Isaac is embedded in is still a factor in the slow development of the storm.

All the Isaac radar composites at 0.5-km height resolution are available at http://www.aoml.noaa.gov/hrd/Storm_pages/isaac2012/radar.html.