Large outbreak of Saharan dust over the eastern Atlantic Ocean

February 7th, 2012
EUMETSAT Meteosat-9 0.635 µm visible channel images (click image to play animation)

EUMETSAT Meteosat-9 0.635 µm visible channel images (click image to play animation)

McIDAS images of EUMETSAT Metosat-9 0.635 µm visible channel images (above; click image to play animation) showed a very large outbreak of airborne Saharan dust streaming off the continent of Africa and moving west-southwestward out over the adjacent waters of the eastern Atlantic Ocean on 07 February 2012. In addition, a pair of long von Karman vortex streets can be seen moving southwestward from the Cape Verde islands.

While the viewing angle was more extreme, the Saharan dust could also be seen on GOES-13 0.63 µm visible channel images (below).

GOES-13 0.63 µm visible channel images + surface reports

GOES-13 0.63 µm visible channel images + surface reports

The emergence of this Saharan dust over water can be seen to occur around 00:00 UTC on 06 February on the Meteosat-9 Saharan Air Layer tracking product (below).

EUMETSAT Meteosat-9 Saharan Air Layer tracking product

EUMETSAT Meteosat-9 Saharan Air Layer tracking product

“Sting Jet” signature associated with a high wind event in Scotland

January 3rd, 2012
EUMETSAT Meteosat-9 7.35 µm water vapor channel images (click image to play animation)

EUMETSAT Meteosat-9 7.35 µm water vapor channel images (click image to play animation)

 

A rapidly intensifying mid-latitude cyclone (named “Cyclone Ulli” by the Europeans | surface analysis) was responsible for a high wind event as it moved over Scotland on 03 January 2012. A sequence of EUMETSAT Meteosat-9 7.35 µm water vapor channel images (above; click image to play animation) revealed two notable signatures: (1) the formation of a pronounced area of warm/dry water vapor brightness temperatures (bright yellow to orange color enhancement) over the open water north of Ireland, which indicated a strongly forced region of rapidly descending middle-tropospheric air, and (2) a classic “Sting Jet” signature (Monthly Weather Review | Wikipedia) which then moved eastward across Scotland. Just to the south of the sting jet signature, a wind gust of 78 knots (90 mph) was recorded at Glasgow at 08:20 UTC, followed by a wind gust of 70 knots (81 mph) at Edinburgh at 08:50 UTC.  There were additional reports of wind gusts in excess of 87 knots (100 mph) at non-METAR sites in Scotland.

The Sting Jet signature can also be seen in EUMETSAT Meteosat-9 10.8 µm IR images (Animated GIF | QuickTime movie) and EUMETSAT Meteosat-9 0.635 µm visible channel images (Animated GIF | QuickTime movie).

A comparison of 1-km resolution NOAA-19 0.63 µm visible channel and 10.8 µm IR channel images at 12:54 UTC (below) showed the structure of the cyclone as it was centered over the North Sea between the British Isles and Norway.

 

NOAA-19 0.63 µm visible channel image + NOAA-19 10.8 µm IR channel image

NOAA-19 0.63 µm visible channel image + NOAA-19 10.8 µm IR channel image

Additional images of this Sting Jet event are available on the EUMETSAT and NASA Wide World of SPoRT sites.

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.