Ice motion in the Chukchi Sea

December 9th, 2014
Suomi NPP VIIRS 0.7 µm Day/Night Band images (click to play animation)

Suomi NPP VIIRS 0.7 µm Day/Night Band images (click to play animation)

AWIPS II images of Suomi NPP VIIRS 0.7 µm Day/Night Band data covering the 05 December – 09 December 2014 period (above; click image to play animation; also available as an MP4 movie file) revealed a fairly abrupt increase in the southwesterly motion of drift ice in the Chukchi Sea (off the northwest coast of Alaska), with giant ice floes beginning to break away north of Barrow (station identifier PABR) on 08 December. Although the northern half of the satellite scene saw little to no sunlight during this time, abundant illumination from the Moon (in the Waning Gibbous phase, at 82% of full) helped to demonstrate the “visible image at night” capability of the VIIRS Day/Night Band.

This change in ice motion was caused by an increase in northeasterly wind over that region, in response to a tightening pressure gradient between a 1040 hPa high pressure centered north of Siberia and a 958 hPa low pressure centered south of Kodiak Island in the Gulf of Alaska (below). The strong winds were also creating the potential for heavy freezing spray over the open waters north and south of the Bering Strait.

Suomi NPP VIIRS 0.7 µm Day/Night Band image, with surface analysis

Suomi NPP VIIRS 0.7 µm Day/Night Band image, with surface analysis

Along the northwest coast of Alaska, northeasterly winds at Point Hope (station identifier PAPO) gusted as high as 62 knots or 71 mph on 09 December (below). Not far to the north at Cape Lisburne (PALU), the peak wind gust was 39 knots or 45 mph.

Point Hope, Alaska meteorogram

Point Hope, Alaska meteorogram

Intense mid-latitude cyclone in the North Atlantic Ocean

October 13th, 2014
GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)

A large mid-latitude cyclone exhibited explosive development over the North Atlantic Ocean (south of Greenland) on 13 October 2014. This storm produced hurricane-force winds, according to surface analyses from the Ocean Prediction Center. GOES-13 6.5 µm water vapor channel images (above; click image to play animation; also available as an MP4 movie file) showed the intrusion of very dry air (yellow to orange color enhancement) associated with the approach of a potential vorticity anomaly early in the day, followed by the the cyclone wrapping up after it reached the occluded phase during the afternoon hours.

GOES-13 0.63 µm visible channel images (below; click image to play animation) revealed the very pronounced signature of cold air advection from the western to the southern quadrants of the storm, in the form of open-cell and closed-cell convective clouds.

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

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

Fog over Lake Superior

July 21st, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

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

The southerly flow of warm, moist air over the still-cold waters of Lake Superior on 21 July 2014 led to the formation of some interesting lake fog patterns, as seen in McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation; also available as an MP4 movie file). The images above are shown in their native GOES-13 satellite projection.

A similar animation of AWIPS images of re-mapped GOES-13 visible channel data with overlays of METAR surface reports and buoy reports (below; click image to play animation) showed that three of the northern Lake Superior buoys were reporting a water temperature of 38 to 39º F. As far north as Thunder Bay, Ontario (CYQT), air temperatures exceeded 90º F and the dew point exceeded 70º F.

GOES-13 0.63 µm visible images, with METAR and Buoy reports (click to play animation)

GOES-13 0.63 µm visible images, with METAR and Buoy reports (click to play animation)

A Terra MODIS Sea Surface Temperature (SST) product at 17:37 UTC (below) revealed that parts of the western half of Lake Superior exhibited SST values in the 40s F (cyan to blue color enhancement).

Terra MODIS Sea Surface Temperature product

Terra MODIS Sea Surface Temperature product

During the overnight hours preceding the images shown above, a Suomi NPP VIIRS IR brightness temperature difference “fog/stratus product” image at 07:43 UTC (below) showed a signal of widespread fog/stratus (yellow to red color enhancement) across much of the eastern half of Lake Superior.

Suomi NPP VIIRS IR brightness temperature difference

Suomi NPP VIIRS IR brightness temperature difference “fog/stratus product”

Great Lakes Water Temperatures: Cold!

July 10th, 2014
Suomi NPP VIIRS Sea Surface Temperature product over the Great Lakes, with bouy data, ~1900 UTC 10 July 2014

Suomi NPP VIIRS Sea Surface Temperature product over the Great Lakes, with bouy data, ~1900 UTC 10 July 2014

Favorable orbital geometry of the Suomi NPP satellite and mostly clear skies over the Great Lakes basin allowed for a nearly complete picture of Great Lakes water temperatures from VIIRS on 10 July (in fact, all Great Lakes were viewed on two successive orbits). As has been noted elsewhere, lake water temperatures are running significantly below normal: pockets of surface water in the 30s F (darker blue color enhancement) persist in Lakes Michigan and Lake Huron, and much of Lake Superior still has surface water temperatures in the 30s to near 40°F.

Over the Lake Michigan area, high pressure with light winds in tandem with the thermal contrast between the cold waters (closer view) and the rapidly-warming land surfaces led to the generation of a well-defined lake breeze, which could be seen on GOES-13 0.63 µm visible channel images (below; click image to play animation; also available as an MP4 movie file). Early in the animation, note the formation of a thin patch of fog/stratus over the area of colder waters in northern Lake Michigan, as southeasterly/southerly winds advected warmer air over the cold water (MODIS visible/SST image comparison). The haziness seen moving over the western portion of Lake Michigan at the end of the animation is smoke transported from wildfires in northwestern Canada (Terra MODIS AOD and trajectories)

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

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