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”

Large “hole punch cloud” over Wisconsin

July 18th, 2014

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

A large (approximately 50-mile diameter) “hole punch cloud” or “fall steak cloud” was seen over northwestern Wisconsin during the morning hours of 18 July 2014. An AWIPS 4-panel comparison of GOES-13 0.63 µm visible channel, 3.9 µm shortwave IR channel, 10.7 µm IR window channel, and 6.5 µm water vapor channel images (above; click image to play animation) showed that 10.7 µm IR cloud top brightness temperatures were not particularly cold with this feature (generally in the 0º C to -4º C range), and while 3.9 µm shortwave IR brightness temperatures warmed within the broad cloud deck surrounding the hole punch cloud after sunrise (due to reflection of solar radiation off of water cloud droplets), the center of the feature continued to exhibit colder (lighter gray enhancment) IR brightness temperatures which suggests cloud glaciation.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

A comparison of CLAVR-x POES AVHRR Cloud Type, Cloud Top Height (CTH), and Cloud Top Temperature (CTT) products at 09:32 UTC or 4:32 am Central time (above) showed patches of water droplet clouds with CTH values in the 3-4 km range and CTT values in the 0º C to -4º C range.

A similar comparison at 12:05 UTC or 7:05 am Central time (below) revealed two areas of “cirrus” cloud type (orange color enhancement) exhibiting CTT values in the -35º to -40º C range (darker blue color enhancement) along the northern and southern periphery of the forming hole punch cloud.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

These ranges of AVHRR Cloud Top Temperature and Cloud Top Height values agreed well with the regional rawinsonde data from Davenport IA (KDVN), Minneapolis MN (KMPX) and Green Bay WI (KGRB) shown below.

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Terra MODIS visible and Cloud Phase products at 17:07 UTC or 12:07 pm Central time (below) indicated that a large area of glaciated ice cloud (salmon color enhancement) existed in the center portion of the hole punch cloud feature.

Terra MODIS 0.65 µm visible image and Cloud Phase products

Terra MODIS 0.65 µm visible image and Cloud Phase products

The cause of this large hole punch or fall streak cloud feature — and the other similar but smaller features seen across the region — was likely aircraft that had either ascended or descended through the cloud layer; particles in the aircraft exhaust acted as ice condensation nuclei, causing the process of cloud glaciation to begin.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 imagery (above) shows the Hole Punch cloud from an oblique angle, and highlights how the region was overrun by smoke from wildfires in Canada. Smoke is most easily seen in visible satellite imagery when the sun is low in the sky, allowing for forward scatter. The smoke becomes less apparent in the imagery as the Sun rises. A similar animation for GOES-13 is below. Smoke is not quite so evident in this image because there is less forward scatter to GOES-13 over 75º W. Animations from both satellites show a hole punch cloud in Iowa as well.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

Rammasun makes landfall in southern China

July 18th, 2014

COMS-1 10.8 µm infrared channel images [click to play animation]

COMS-1 10.8 µm infrared channel images [click to play animation]

Super Typhoon Rammasun has made landfall in southern China – apparently this was the strongest typhoon to hit the South China region in 41 years (news story). The COMS-1 IR animation, above, shows the storm skirting along the north shore of the island of Hainan before hitting the south shore of the Leizhou Peninsula. A plot of the CIMSS Advanced Dvorak Technique indicated that Rammasun went though a period of rapid intensification on 17 July before reaching Super Typhoon intensity around 00 UTC on 18 July. The projected path (from this site) of the storm has it moving across the Gulf of Tonkin (where very warm Sea Surface Temperatures are present) and making landfall near the Vietnam/China border.

Past and Projected path of Rammasun, with Sea Surface Temperatures [click to enlarge]

Past and Projected path of Rammasun, with Sea Surface Temperatures [click to enlarge]

Visible imagery (below) captured the eye as it approached Hainan and then moved into the Qiongzhou strait between the island and the mainland. Note the initially mostly clear eye (with embedded small-scale vortices) rapidly fills after landfall.

COMS-1 0.675 µm infrared channel images [click to play animation]

COMS-1 0.675 µm infrared channel images [click to play animation]

A DMSP SSMIS 85 GHz microwave image (below) showed a well-defined eyewall at 1016 UTC.

DMSP SSMIS 85 GHz microwave image

DMSP SSMIS 85 GHz microwave image

A comparison of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm “visible image at night” Day/Night Band data at 1735 UTC on 17 July (below; courtesy of William Straka, SSEC) revealed an interesting packet of waves in the southeastern quadrant of the eyewall region of the tropical cyclone.

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

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)