Mesovortex over Lake Ontario

February 17th, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 (GOES-East) 0.63 µm visible channel images (above; click to play animation) revealed the presence of a mesocale vortex (“mesovortex”) propagating eastward across the ice-free waters of western Lake Ontario on on 17 February 2015. At the beginning of the animation, also note that there were numerous “hole punch clouds” seen in the stratus cloud deck that covered the western Lake Ontario region during the early morning hours; these holes were likely caused by aircraft inbound/outbound from the Toronto International Airport — particles in jet engine exhaust act as ice nuclei, causing supercooled water droplets to turn into larger, heavier ice particles which then fall out of the cloud to create holes (sometimes described as “fall streaks” due to their appearance).

A closer view using a sequence of MODIS and VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server site is shown below. There was a significant amount of ice in the northeastern section of Lake Ontario, as well as a ring of offshore ice around other parts of the lake.

MODIS and VIIRS true-color images

MODIS and VIIRS true-color images

A comparison of the 16:31 UTC Terra MODIS 0.65 µm visible channel and the corresponding Sea Surface Temperature product (below) showed that SST values in the ice-free portions of the mesovortex path were generally in the 30 to 34º F  range.

Terra MODIS 0.65 µm visible channel image and Sea Surface Temperature product

Terra MODIS 0.65 µm visible channel image and Sea Surface Temperature product

African dust blowing across the Mediterranean Sea

February 2nd, 2015
Suomi NPP VIIRS true-color image composites

Suomi NPP VIIRS true-color image composites

A sequence of daily Suomi NPP VIIRS Red/Green/Blue (RGB) true-color image composites from the SSEC RealEarth web map server site (above) showed the northeastward transport of African dust across the Mediterranean Sea during the 31 January – 02 February 2015 period. On 02 February, orange snow was observed in Saratov, Russia (news story), a city about 580 miles or 936 km northeast of Stavropol (which is located in the far upper right corner of the VIIRS images).

Airborne glacial silt over the Gulf of Alaska

February 1st, 2015
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

Due to a tight pressure gradient between a high over the Yukon and a low over the Gulf of Alaska (surface analysis), strong offshore winds (with gusts as high as 78 mph) were lofting glacial silt from the northern portion of the Alaska Panhandle region and carrying it westward over the Gulf of Alaska on 01 February 2015. Hints of the narrow light grey plumes could be seen streaming southwestward then westward on GOES-15 (GOES-West) 0.63 µm visible channel images (above; click to play animation).

A closer look using a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 0.64 µm visible channel images (below) showed that the areal extent of the airborne aerosols was much more evident on the DNB image (in part due to it’s more broad spectral response). However, other more intricate patterns were seen on the DNB image in the general vicinity of Middleton Island (station identifier PAMD) that did not appear to match the character of the airborne glacial silt features being blown westward from the Alaska Panhandle region.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 0.64 µm visible channel images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 0.64 µm visible channel images

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from the SSEC RealEarth web map server (below) offers a clue to help explain the meandering features that stretched from the coast east of Prince William Sound toward the Middleton Island area: strands of phytoplankton, fed by nutrients in the river waters draining from the interior into the Gulf of Alaska. Sun glint along the edge of the VIIRS scan may have helped to highlight these features in the DNB image above. In fact, these water features were less obvious — and the airborne glacial silt more obvious — in a subsequent VIIRS DNB vs Visible image at 23:20 UTC.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

The trans-Atlantic flow of moisture and strong winds

January 14th, 2015
SSEC RealEarth™ Infrared satellite image featured on NBC Nightly News

SSEC RealEarth™ Infrared satellite image featured on NBC Nightly News

The SSEC RealEarth geostationary satellite infrared (IR) image composite shown above (which was first sent out via Twitter by Stu Ostro of The Weather Channel…thanks Stu!) was featured on the NBC Nightly News on 14 January 2015 (link) because it illustrated a vivid example of the trans-Atlantic flow of moisture from a disturbance off the US East Coast to a rapidly-deepening storm approaching the British Isles (surface analysis maps | water vapor images with surface analyses).

A sequence of hourly geostationary satellite water vapor channel image composites (below; click to play animation) showed that there was a clear trans-Atlantic connection in terms of middle to upper tropospheric moisture/clouds, and a comparison of the 20 UTC water vapor image with the corresponding MIMIC Total Precipitable Water product indicated that there was a lower to middle tropospheric moisture connection as well. This type of long and narrow fetch of TPW is often referred to as an “atmospheric river”.

Geostationary satellite water vapor image composites (click to play animation)

Geostationary satellite water vapor image composites (click to play animation)

Another interesting point brought up during the NBC Nightly News segment was the recent presence of unusually strong trans-Atlantic jet stream winds, which has allowed aircraft flying from New York City to London to set record times in terms of conventional passenger aircraft (such as the 08 January flight of British Airways 114). Note the strong dry-to-moist (darker blue to white to green color enhancement) along the northern edge of the trans-Atlantic water vapor image moisture feed: such a moisture gradient often coincides with the axis of a strong jet stream. AWIPS images of water vapor imagery with overlays of MADIS cloud-tracked and water-vapor-tracked winds (below; click image to play animation) showed many high-altitude wind vectors in the vicinity of the jet stream moisture gradient with speeds in the 150-160 knot range (with 175 knots seen on the previous day).

Water vapor images with MADIS atmospheric motion vectors (click to play animation)

Water vapor images with MADIS atmospheric motion vectors (click to play animation)