Christmas Full Moon Day/Night Band images

December 25th, 2015

Suomi NPP VIIRS Day/Night Band image swaths [click to enlarge]

Suomi NPP VIIRS Day/Night Band image swaths [click to enlarge]

A rare Full Moon on Christmas — the last occurrence was in 1977, and the next will be in 2034 — was reached at 1111 UTC, and provided some compelling “visible images at night” from the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB). The animation above shows the coverage of 4 consecutive DNB image swaths across much of North America, as viewed using RealEarth.

Taking a closer look at various regions and features, we will begin with the Northeast US at 0610 UTC (below). One item of interest was the narrow fingers of valley fog that were forming in parts of Pennsylvania and New York, where strong radiational cooling under cloud-free skies was allowing the surface air temperatures to cool into the 30s and 40s F.

Suomi NPP VIIRS 0.7 µm Day/Night Band image centered over the Northeast US [click to enlarge]

Suomi NPP VIIRS 0.7 µm Day/Night Band image centered over the Northeast US [click to enlarge]

Over the Southeast US at 0749 UTC (below), ample illumination by the Full Moon provided a very detailed nighttime view of the tops of numerous thunderstorms that had developed along and ahead of a cold frontal boundary (surface analysis). Note the appearance of several bright white areas at the tops of some thunderstorms, a signature of cloud illumination by intense lightning activity. In addition, temperatures ahead of the cold front were unusually warm for 25 December — for example, new records for the warmest low temperature for the date were set at both Mobile, Alabama and Pensacola, Florida (with 75º F and 71º F, respectively).

Suomi NPP VIIRS Day/Night Band image centered over the Southeast US [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over the Southeast US [click to enlarge]

Farther to the north, a DNB image centered over South Dakota (below) showed a great deal of variability in snow cover across that area; the effect of deeper snow cover on surface air temperatures could also be seen in the surface observations at that time, with the colder readings generally coinciding with sites having snow on the ground.

Suomi NPP VIIRS Day/Night Band image centered over South Dakota [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over South Dakota [click to enlarge]

Even farther to the north, it could be seen that ice covered a significant portion of Hudson Bay, Canada (below). In southern parts of Hudson Bay where open water still existed, numerous “lake effect” cloud bands could be seen due the northwesterly flow of very cold arctic air across the water.

Suomi NPP VIIRS Day/Night Band image centered over Hudson Bay, Canada [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over Hudson Bay, Canada [click to enlarge]

A DNB image centered over the Western US at 0930 UTC (below) revealed features such as snow pack over the higher terrain of the Sierra Nevada in California (where temperatures at the time ranged from 55º F in the desert at Needles KEED to 1º F in the mountains at South Lake Tahoe KTVL), and a variety of open-cell and closed-cell convection over the adjacent offshore waters of the Pacific Ocean.

Suomi NPP VIIRS Day/Night Band image centered over the western US [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over the western US [click to enlarge]

Finally, a DNB image centered over Alaska and the Yukon Territory of Canada at 1111 UTC (below) showed widespread snow cover over the cloud-free interior regions, with the thick cloud shield from a Gulf of Alaska storm moving over southwestern and southcentral Alaska. Very cold surface air temperatures at or below -30º F could be seen at a number of sites in the interior areas, with -42º F being reported at the time in Arctic Village, Alaska PARC (their minimum temperature later dropped to -45º F).

Suomi NPP VIIRS Day/Night Band image centered over Alaska and the Yukon Territory [click to enlarge]

Suomi NPP VIIRS Day/Night Band image centered over Alaska and the Yukon Territory [click to enlarge]

Some Solstice Satellite Scenes

December 22nd, 2015

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

The 2015 December solstice — Winter in the Northern Hemisphere, and Summer in the Southern Hemisphere — occurred at 0448 UTC on 22nd day of the month. Several hours prior to the solstice, the daylight/darkness “terminator” (tilted at 23.5º due to the inclination of the Earth’s axis) could be seen moving from east to west across North America on GOES-13 (GOES-East) Visible (0.63 µm, 1-km resolution) images (above).

The terminator was also seen on GOES-15 (GOES-West) Visible (0.63 µm, 1-km resolution) images (below), albeit a few hours later. Note that areas of northern Canada and northern Alaska remain dark during the entire day; for example, at Barrow (the northernmost city in Alaska), their polar night — the period with no sunlight — lasts about 65 days, from mid-November to late January.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

For a global perspective, we can examine Himawari-8  true-color Red/Green/Blue (RGB) images (below), which cover the period before, during, and after the 0448 UTC solstice time — the animation pauses briefly on the 0450 UTC image, nearest the time of the solstice (also available as longer MP4 movie file). One feature that stands out quite prominently (due to a favorable forward scattering angle) is the dense haze covering much of the Indian subcontinent and the adjacent offshore waters. These images were generated using an update (version 2) of the Simple Hybrid Contrast Stretch (SHCS) method, which uses the AHI 0.86 µm band to “boost” the green of the 0.51 µm band, and stretches each of the 3 color components (R/G/B) on both the dark and light ends. Similar full-disk true-color images will be available every 5 minutes from the ABI instrument on GOES-R.

Himawari-8 true-color images [click to play animation]

Himawari-8 true-color images [click to play animation]

The Himawari-8 data was provided by JMA and acquired via NOAA/NESDIS/STAR; the SSEC Data Center served the AHI data via McIDAS ADDE, and McIDAS-X was used for the processing.

Bore-like Gravity Wave Signatures over Texas

December 15th, 2015

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 (above) and GOES-15 (below) both captured the propagation of gravity waves that displayed Bore-like attributes along an inversion with a cold front over central Texas. (Click here for an animation of GOES-13 and GOES-15 side-by-side that includes observed surface winds).

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

There was a temperature drop across the front, and modest wind gusts occurred just after the lowest pressure associated with the feature passed, but those gusts occurred only in a narrow corridor in central Texas: KSNK (Snyder) reported gusts of 14 knots (0925 UTC); KSWW (Sweetwater) reported gusts of 15 knots (1035 UTC); KABI (Abilene) reported gusts to 17 knots (1152 UTC); KBWD (Brownwood) reported gusts to 24 knots at 1335 UTC; KMKN (Comanche) reported gusts of 22 knots at 1355 UTC (See also the image below). The narrowness of this corridor is likely related to the strength of the inversion along which the bore is propagating (The 1200 UTC Soundings from Fort Worth and from Del Rio both show a very strong inversion; perhaps there was a weakness in the inversion over central Texas that allowed for more vertical mixing).

GOES-13 Visible (0.63 µm) imagery at 1400 UTC; Station Locations are indicated, including the 5 stations with identifiable Wind Gusts associated with the Bore Feature [click to enlarge]

GOES-13 Visible (0.63 µm) imagery at 1400 UTC; Station Locations are indicated, including the 5 stations with identifiable Wind Gusts associated with the Bore Feature (Gust Strength in knots and time of Gust indicated) [click to enlarge]

During the preceding nighttime hours, the early stage of the undular bore feature was detected on an Aqua MODIS Water Vapor (6.7 µm) image, below, along the leading edge of the colder air and colder surface brightness temperatures (light to medium blue colors) seen on the corresponding MODIS Infrared (11.0 µm) image at 0807 UTC or 2:07 am local time.

Aqua MODIS Water Vapor (6.7 µm) and Infrared (11.0 µm) images [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) and Infrared (11.0 µm) images [click to enlarge]

(Hat tip to Mike Johnson, NWS in San Angelo for tweeting about this feature!)

How long can Tornado Scars last?

July 22nd, 2015
MODIS True-Color Image,  June 9, 2007 (left) and  July 15, 2015 (right) (click to enlarge)

MODIS True-Color Image, June 9, 2007 (left) and July 15, 2015 (right) (click to enlarge)

On 07 June 2007, severe thunderstorms moved through the Upper Midwest (blog post on that event), spawning strong tornadoes; from the SPC Storm Reports comments:

HUNDREDS OF TREES DOWN NORTH OF ZOAR. (GRB)

NUMEROUS TREES DOWN OF 1 FOOT DIAMETER AND GREATER. TRACK WAS APPROXIMATELY 1/4 MILE IN LENGTH AND 125 YARDS WIDE (MQT)

Terra MODIS data on 09 June 2007 (in the image above, at left) showed a tornado scar (much longer than 1/4 mile in length) running southwest-to-northeast through heavily forested Menominee County into Langlade County and then Oconto County in northeast Wisconsin. Terra MODIS True-Color imagery from 15 July 2015 (also in the image above, at right) (cropped from imagery at the MODIS Today website), shows that a scar persists more than 8 years later! (This persistent scar has been mentioned before on this blog here in 2009 and here in 2011).

Landsat-8 overflew northeast Wisconsin on 15 July 2015, at nearly the same time as the Terra MODIS imagery above, and those views, captured via SSEC‘s RealEarth are shown below. The scar is more evident in the shortwave infrared (Band 6, 1.61 µm) than the visible (Band 3, 0.56 µm) because the shortwave infrared channel is more sensitive to changes in vegetation. Lakes are also far more apparent in the 1.61 µm imagery because water absorbs 1.61 µm radiation; little is scattered back to the satellite for detection and water therefore appears black.

Landsat-8 band 3 (0.56 µm) and Band 6 (1.61 µm) imagery, ~1640 UTC July 15, 2015 (click to enlarge)

Landsat-8 band 3 and Band 6 imagery, ~1640 UTC July 15, 2015 (click to enlarge)


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In April 2011, an historic tornadic event occurred over the Deep South that spawned numerous strong long-tracked tornadoes (blog post). The tornado paths from this event were also visible from both MODIS and GOES imagery (Link). The animation below shows MODIS true color imagery from before the tornadoes, from several days after, and from early May this year. Three distinct tornado scars remain in Alabama: One runs from Tuscaloosa to Birmingham, a second is south of Tuscaloosa, and a third is north of Tuscaloosa.

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)