McIDAS images of 1-km resolution GOES-13 Visible (0.63 µm) data (above ) revealed numerous aircraft dissipation trails and “hole punch clouds” which formed over southern Florida and the adjacent waters of the Atlantic Ocean on 12 December 2014. These features are formed when an aircraft penetrates a supercooled cloud layer — the particles in the exhaust act as ice nuclei which allow the supercooled water droplets to transform into ice crystals.

A comparison of 250-meter resolution Terra MODIS True Color and False Color Red-Green-Blue (RGB) images from the SSEC MODIS Today site (below) confirmed that the clouds within the dissipation trails and hole punch features had glaciated — ice crystal clouds appear as shades of cyan in the False Color image, in contrast to supercooled water droplet clouds which appear as varying shades of white.

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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.

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.

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As seen on a plot of the Advanced Dvorak Technique (ADT) intensity estimation (above), Typhoon Hagupit underwent a period of rapid intensification in the West Pacific Ocean late in the day on 03 December 2014, reaching Super Typhoon (Category 5) intensity on 04 December. During this period of rapid intensification, COMS-1 10.8 µm IR channel images (below; click to play animation; also available as an MP4 movie file) showed the development of a well-defined eye, with very cold cloud-top IR brightness temperatures (in the -80 to -90º C range, shades of violet) in the surrounding eyewall region.

A nighttime comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 15:50 UTC on 03 December (below; images courtesy of William Straka, SSEC) showed great detail in the cloud top IR brightness temperature patterns, as well as demonstrated the “visible image at night” capability of the Day/Night Band (which benefited from an abundance of reflected moonlight from a nearly-full Moon).

A longer-term sequence (beginning on 30 November) of storm-centered COMS-1 IR images is shown below (click image to play animation).

COMS-1 0.675 µm visible channel images from the CIMSS Tropical Cyclones site (below; click image to play animation) revealed the presence of mesovortices within the eye of Hagupit, with intricatecloud-top banding structures seen surrounding the eye.

A DMSP SSMIS 85 GHz microwave image at 22:43 UTC on 04 December (below) also showed the well-defined eyewall structure of the storm.

For additional images and information on Super Typhoon Hagupit, see the VISIT Meteorological Interpretation blog.

===== 06 December Update =====

A comparison of MTSAT 10.8 µm IR and TRMM TMI 85 GHz microwave images just after 16:30 UTC on 06 December (below) showed the center of Hagupit making landfall on the island of Samar in the Philippines as a Category 3 typhoon. The slow-moving tropical cyclone dropped as much as 300-400 mm (12-16 inches) of rainfall.

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As of 25 November 2014, much of the state of California was experiencing extreme to exceptional drought conditions.  However, the development of a large occluded mid-latitude cyclone over the far eastern Pacific Ocean during the 01 December – 02 December time period began to draw high values (up to 60 mm or 2.4 inches, darker red color enhancement) of total precipitable water (TPW) northward from the Inter-Tropical Convergence Zone (ITCZ), as seen on AWIPS images of the MIMIC TPW product (above). While the rainfall was beneficial in terms of drought mitigation, amounts of up to 12 inches did cause flooding and mudslide problems in some locations.

An animation of hourly MIMIC TPW images from 30 November – 02 December (below; click image to play animation) showed the northward surge of moisture toward the California coast, and also hinted at a complex inner structure associated with the occluded low.

On 02 December, comparisons of AWIPS II images of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-15 6.5 µm water vapor channel data around 11 UTC (above) and around 22 UTC (below) demonstrated the importance of improved spatial resolution for more clearly identifying some of the smaller-scale structure features within the core of the occluded low.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 22:18 UTC (below) shows a few areas of embedded convection, some of which had produced cloud-to-ground lightning strikes in the hour preceding the images.

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