Post-Tropical Cyclone Leslie makes landfall in Portugal

October 13th, 2018 |

Aqua MODIS True Color RGB image [click to enlarge]

Aqua MODIS True Color RGB image, with and without surface reports [click to enlarge]

20 days after Leslie initially formed (and 17 days after it underwent extratropical transition), an Aqua MODIS True Color Red-Green-Blue (RGB) image viewed using RealEarth (above) showed the storm at 1419 UTC on 13 October 2018, when it was still classified as a Category 1 Hurricane off the coast of Portugal. The southwest-to-northeast oriented cloud band just west of Leslie was associated with an advancing cold front (surface analyses), which soon began to absorb the tropical cyclone and aid in its extra-tropical transition a few hours prior to landfall.

EUMETSAT Meteosat-11 middle/upper-tropospheric Water Vapor (6.25 µm) images (below) exhibited a warm/drying trend (brighter shades of yellow) along the western and southern edges of Leslie as it moved inland across Portugal. Hourly Meteosat-11 Water Vapor images visualized using RealEarth are available here.

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

Along the coast of Portugal a thunderstorm was reported at Porto (LPPR) from 1930-2000 UTC (about an hour before landfall). Farther to the south, shortly after landfall the surface winds gusted to 55 knots (63 mph or 28.3 m/s) at Monte Real Air Base (LPMR) at 21 UTC and 42 knots (48 mph or 21.6 m/s) at Ovar Military Base (LPOV) at 23 UTC. The highest wind gust was 95 knots (110 mph or 49 m/s) at Figueira da Foz, located along the coast between LPMR and LPOV:

Meteosat-11 lower/middle-tropospheric Water Vapor (7.35 µm) images (below) revealed the characteristic “scorpion tail” signature of a Sting Jet (Monthly Weather Review | Wikipedia), along with a mesoscale region of warming/drying (darker shades of orange) driven by strong subsidence — this subsidence feature corresponded well with the report of strong winds at Figueira da Foz. Further discussion of this sting jet event is available here.

Meteosat-11 Water Vapor (7.35 µm) images, with hourly splots of surface winds and gusts in knots [click to play animation | MP4]

EUMETSAT Meteosat-11 Water Vapor (7.35 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

Radar composites from the Portuguese Institute for Sea and Atmosphere (IPMA) confirmed that post-tropical cyclone Leslie made landfall around 2100 UTC (below).

Radar reflectivity composites [click to play animation]

Radar reflectivity composites [click to play animation]

Although the view from GOES-16 (GOES-East) was very oblique, the warm/dry signature around the western and southern edges of the storm was still evident on Mid-level Water Vapor (6.9 µm) imagery (below).

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface winds and gusts in knots [click to play animation | MP4]

The entire life cycle of Leslie — from becoming a named Subtropical Storm at 15 UTC on 23 September to making landfall as a post-tropical cyclone in Portugal at 21 UTC on 13 October — is shown with 15-minute GOES-16 “Clean” Infrared Window (10.3 µm)  and Mid-level Water Vapor (6.9 µm) images (below). Note that 5-minute imagery was available on 01 October, when GOES-16 was performing a test of the Mode 4 scan strategy.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images [click to play MP4 animation]