CMORPH estimates of hourly (and daily) rainfall with Sally

September 16th, 2020 |

CMORPH hourly estimates of precipitation over Mississippi and surrounding states, 1300-2200 UTC 16 September 2020 (Click to enlarge)

Hurricane Sally weakened to a Tropical Storm at 1800 UTC on 16 September. Sally is a prodigious rainfall producer. CMORPH (CPC Morphing Technique) Precipitation estimates (blogged about earlier) are available at this Real Earth website. Hourly estimates from 1300 through 2200 UTC are shown above.  Many locations over southern Mississippi show hourly multi-inch accumulations for much of the day.

Daily precipitation for the 24 hours ending at 00 UTC on 17 September is shown below.  A large area of Mississippi shows values between exceeding 100-150 mm.  Click here to see a 24-h precipitation total image for the period ending 1200 UTC on 17 September (from this website) A series of daily images of 24-hour precipitation (at bottom) shows the evolution of the diagnosed precipitation from 09-16 September.

Daily CMORPH Precipitation Accumulation, valid 0000 UTC on 17 September 2020 (Click to enlarge)

Daily CMORPH estimates of precipitation, 09-16 September 2020 (Click to enlarge)

Hurricane Sally makes landfall in Alabama

September 16th, 2020 |

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) [click to play animation | MP4]

At 0500 UTC on 16 September 2020, Hurricane Sally rapidly intensified (ADT | SATCON) to a Category 2 storm, and soon thereafter made landfall near Gulf Shores, Alabama at 0945 UTC. During that time period, 1-minute GOES-16 Infrared imagery — with and without an overlay of GLM Flash Extent Density (above) — displayed a ragged eye structure, along with a lack of GLM-detected lightning activity in the immediate vicinity of the storm center. The eye passed just to the west of Buoy 42012, where the wind gusted to 95.2 knots or 110 mph at 0510 UTC (below).

Plot of wind speed (blue), wind gusts (red) and pressure (green) at Buoy 42012

Plot of wind speed (blue), wind gusts (red) and pressure (green) at Buoy 42012


How did Sally change the Sea Surface Temperatures (SSTs) in the Northern Gulf? The toggle below of Advanced Clear Sky Processor for Ocean (ACSPO) SSTs from VIIRS, derived using CSPP (the Community Satellite Processing Package) and direct broadcast data at CIMSS, shows SSTs about 2ºF cooler (cyan in the enhancement, about 80ºF) compared to surrounding waters that are 82-83ºF..

ACSPO SSTs at 0746 and 1912 UTC on 17 September 2020 (click to enlarge)