Weak tornado in San Juan, Puerto Rico

October 6th, 2017 |

An email from SSEC/CIMSS employee Shane Hubbard discussed details of a weak tornado in San Juan, Puerto Rico on 06 October 2017:

While I was working in San Juan last week a tornado formed close to the shoreline of Lake (Lagoon) Los Corozos, moved over the water, and then damaged homes in a neighborhood named ‘Playita’ where I was working. The tornado formed near 18.439089, -66.041962 on October 6th around 4:25pm AST. 10+ roofs were damaged from the event. Many of those roofs had already been repaired by residents or by the carpenters that were volunteering in the community. It was a very depressing event to say the least.

Here are links to the tornado.

Approximate tornado path (courtesy of Shane Hubbard)

Approximate tornado path (courtesy of Shane Hubbard)

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly San Juan surface data plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly San Juan surface data plotted in yellow [click to play MP4 animation]

A GOES-16 Mesoscale Sector remained positioned over Puerto Rico (to support their lack of weather radars, which were destroyed by Hurricane Maria; click here for a Tweet from NWS San Juan showing their radar damage) — “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the region around San Juan (station identifier TJSJ).  An Infrared animation covering the time from 1915 UTC to 2054 UTC, displayed at the GOES-16 ABI full 12-bit depth (created using SIFT) is shown here; a visible animation is available here.

Convective initiation occurred over the far eastern end of the island about an hour before the tornado — cloud-top infrared brightness temperatures cooled to around -70ºC (black enhancement) around the time of the tornado (2025 UTC) during a second burst of convection.

Of particular note is the speed with which the second convective storm grew.  Between 2020 UTC and 2025 UTC, the cloud-top infrared brightness temperatures cooled 20ºC in the region of thunderstorm development!  The bar graphs below show the brightness temperature distribution in the region of convective development.

Cloud-Top Brightness Temperatures over a Tornadic Convective Storm at 2020 and 2025 UTC on 6 October 2017 (Click to enlarge)

The animation below shows GOES-16 10.3 µm Clean Infrared Window images for 10 minutes: 2017-2026 UTC on 6 October. Very strong convective development is apparent, overlapping with the 2025 UTC time of the tornado.

GOES-16 “Clean Window” 10.3 µm Imagery, 2017-2026 UTC on 6 October 2017 (Click to enlarge)