Hurricane JoaquinJoaquin reached Category 1 hurricane intensity on the morning of 30 September 2015 (NHC advisories). An eye structure was becoming apparent on a 1259 UTC Microwave (85 GHz) image from the SSMIS instrument on the DMSP-18 satellite (above).
The GOES-13 (GOES-East) satellite was placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-7 minutes. Visible (0.63 µm) images (below; also available as an MP4 movie file) showed a number of convective bursts during the day, with a few overshooting tops.GOES-13 Infrared (10.7 µm) images (below; also available as an MP4 movie file) showed that cloud-top IR brightness temperatures associated with these convective bursts were in the -80º to -90º C range (violet colors). An organized eye structure was beginning to appear on the IR images at the end of the day.
===== 01 October Update =====
The ASCAT Scatterometer on board METOP-A sampled the eastern half of Joaquin shortly after 0230 UTC on 1 October, as shown below. Hurricane-force winds were observed 20-30 miles away from the storm center; tropical storm-force winds extended about twice as far out.Joaquin intensified into a Category 4 hurricane late in the day on 01 October (ADT intensity plot) as the storm slowly moved of the warm sea surface temperature and high ocean heat content waters in the vicinity of the Bahamas. Joaquin became the first Category 4 hurricane to move though the Bahamas in October since 1866 (Capitol Weather Gang blog). A fairly persistent but rather ragged-appearing eye was seen on GOES-13 Infrared (10.7 µm) images (below; also available as an MP4 movie file). Once again, the well-defined eye structure was more evident on DMSP SSMIS microwave imagery. GOES-13 Visible (0.63 µm) images (below; also available as an MP4 movie file) showed a continuation of the development of convective bursts with overshooting tops in the eyewall region of the hurricane.