Strong winds in Scotland associated with the passage of a warm seclusion cyclone

December 28th, 2011 |
EUMETSAT Meteosat-9 High Resolution Visible (HRV) images

EUMETSAT Meteosat-9 High Resolution Visible (HRV) images

EUMETSAT Meteosat-9 High Resolution Visible (HRV) images (above) showed the classic signature of a “warm seclusion“: a nearly cloud free eye-like structure at the center of the circulation. Surface station wind barbs (in knots) are also plotted in cyan on the images.

A similar eye-like appearance was seen on Meteosat-9 water vapor channel images (below) as the mature cyclone moved just north of the British Isles on 28 December 2011.

EUMETSAT Meteosat-9 water vapor channel images

EUMETSAT Meteosat-9 water vapor channel images

Hurricane force wind gusts were observed at Tiree, Scotland (station identifier EGPU), with a peak gust of 69 knots (79 mph) at 14:20 UTC (below).

Tiree, Scotland (EGPU) surface reports

Tiree, Scotland (EGPU) surface reports

Surface analyses from the NWS/NCEP Ocean Prediction Center (below) showed the intensification and evolution of the cyclone during the day.

Ocean Prediction Center surface analyses

Ocean Prediction Center surface analyses

Warm seclusions are also sometimes observed with intense cyclones along the East Coast of the US, as in this 20 December 2009 case.

Tropical Storm Thane (06B) in the Bay of Bengal, and Tropical Storm Benilde (04S) in the South Indian Ocan

December 28th, 2011 |
MTSAT-1R 10.8 µm IR channel images

MTSAT-1R 10.8 µm IR channel images

 

MTSAT-1R 10.8 µm IR channel images from the CIMSS Tropical Cyclones site (above) showed Category 1 Tropical Storm Thane (06B) in the Bay of Bengal, moving toward the east coast of India on 28 December 2011.

Contours of 850-200 hPa satellite-derived deep layer wind shear overlaid on MTSAT-1R 6.75 µm water vapor channel images (below) indicated that Thane was in an environment of low wind shear, which favored some intensification prior to making landfall.

MTSAT-1R 6.75 µm water vapor channel images + Deep layer wind shear

MTSAT-1R 6.75 µm water vapor channel images + Deep layer wind shear

It is interesting to note that the MIMIC Total Precipitable Water product (below) showed the northern counterclockwise circulation of Tropical Storm Thane and the southern clockwise circulation of Tropical Storm Four (04S) — each drawing moisture from the Inter-Tropical Convergence Zone (ITCZ).

MIMIC Total Precipitable Water product

MIMIC Total Precipitable Water product

===== 30 December Update =====

Tropical Storm 04 S intensified in a similar low wind shear environment, becoming Tropical Cyclone Benilde in the South Indian Ocean. Benilde was forecast to intensify, with wind gusts up to 140 knots. Meteosat-7 visible/shortwave IR images with an overlay of ASCAT scatterometer surface winds (below) showed the structure of Benilde.

Meteosat-7 visble/shortwave IR imagery + ASCAT surface winds

Meteosat-7 visble/shortwave IR imagery + ASCAT surface winds