Rapid cyclogenesis off the coast of Japan, with an aircraft experiencing severe turbulence

December 16th, 2014 |
COMS-1 6.95 µm water vapor channel images (click to play animation)

COMS-1 6.95 µm water vapor channel images (click to play animation)

McIDAS images of KARI COMS-1 6.95 µm water vapor channel data (above; click image to play animation; also available as an MP4 movie file) showed the tell-tale signatures — well-formed dry slot; distinct comma head — of rapid cyclogenesis for a pair of storms off the west and east coasts of Japan on 16 December 2014. An American Airlines passenger jet flying from Seoul, South Korea (RKSO) to Dallas/Fort Worth, Texas experienced severe turbulence at an altitude around 27,000 feet over the eastern portion of Honshu Island, Japan (media report); several passengers and crew members were injured (with some requiring hospitalization), forcing the aircraft to divert from its course and turn back to make a landing at Tokyo Narita airport (RJAA). The turbulence encounter likely occurred near the center portion of the red square which was drawn on the images whose times were within about 30 minutes of the 10:35 UTC turbulence encounter  (FlightAware track log) — note the development of a “transverse banding” signature along the western edge of the southern storm comma head feature (10:00 UTC image).  After the multi-layered clouds of the comma head departed, lee waves or “mountain waves” could be seen downwind of the high terrain of Honshu Island. It should also be noted that the flight path was in the left exit region of an intensifying upper-tropospheric jet streak (250 hPa winds).

In the Turbulence Risk product shown below, the blue to violet colored areas are the Tropopause Fold Turbulence Product (an algorithm developed at CIMSS which uses geostationary water vapor channel data). These colored areas identify the sections of the upper-tropospheric air mass boundaries that are the most likely to have turbulence. However, it does not attempt to show all areas of turbulence. The transverse band formation over Japan was a signature of intense instability along the jet stream axis, which was probably the cause of the major turbulence event for American Airlines Flight 280.

Turbulence Risk product

Turbulence Risk product

A dry slot exhibiting much warmer brightness temperatures (brighter yellow to orange color enhancement) was seen with the more southern of the two storms, which became the dominant system as it moved northeastward and rapidly intensified from a central pressure of 998 hPa at 06 UTC to 971 hPa at 18 UTC (below). The storm was forecast to produce a large area of hurricane-force winds over the far northwestern Pacific Ocean.

MTSAT-2 6.75 µm water vapor channel images with surface analyses at 06, 12, and 18 UTC

MTSAT-2 6.75 µm water vapor channel images with surface analyses at 06, 12, and 18 UTC

An AWIPS image of MTSAT-2 water vapor channel data with overlays of the NWS Ocean Prediction Center surface analysis and Metop ASCAT scatterometer winds showed surface wind speeds as high as 55 knots (63 mph) with the southern storm and 53 knots (61 mph) with the northern storm at 11:48 UTC (below). During the day wind gusts as high as 81 knots (93 mph) were reported at the Izu Islands south of Tokyo Bay.

MTSAT-2 6.75 µm water vapor channel image, with Metop ASCAT scatterometer surface winds and surface analysis

MTSAT-2 6.75 µm water vapor channel image, with Metop ASCAT scatterometer surface winds and surface analysis

Aircraft dissipation trails and “hole punch clouds” over Florida

December 12th, 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)

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (below; click image to play animation; also available as an MP4 movie) 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/GreenBlue (RGB) images from the SSEC MODIS Today site (below) confirmed that the clouds within the dissipation trails and the hole punch features had glaciated — ice crystal clouds appear as shades of cyan in the false-color image, in contrast to supercooled water droplet cloud which appear as varying shades of white.

Terra MODIS true-color and false-color images

Terra MODIS true-color and false-color images

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

Super Typhoon Hagupit

December 4th, 2014 |
Advanced Dvorak Technique (ADT) intensity estimation plot

Advanced Dvorak Technique (ADT) intensity estimation plot

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.

COMS-1 10.8 µm IR channel images (click to play animation)

COMS-1 10.8 µm IR channel images (click to play animation)

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).

Suomi NPP VIIRS 0.64 µm and 11.45 µm IR image comparison

Suomi NPP VIIRS 0.64 µm and 11.45 µm IR image comparison

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 10.8 µm storm-centered IR images (click to play animation)

COMS-1 10.8 µm storm-centered IR images (click 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.

COMS-1 0.675 µm visible channel images (click to play animation)

COMS-1 0.675 µm visible channel images (click to play animation)

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.

DMSP SSMIS 85 GHz microwave image

DMSP SSMIS 85 GHz microwave image

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.

MTSAT 10.8 µm IR and TRMM TMI 85 GHz microwave images

MTSAT 10.8 µm IR and TRMM TMI 85 GHz microwave images