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, forcing the plane 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 10:36 UTC turbulence report — note the development of a “transverse banding” signature along the western edge of the southern storm comma head feature (10:00 UTC image). The flight path was also in the left exit region of an intensifying upper-tropospheric jet streak (250 hPa winds).

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 western 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

Mesoscale Convective System over the Southern Plains

October 6th, 2014
<strong>Suomi NPP VIIRS Day/Night Band (0.70 µm), Infrared Imagery (11.45 µm) and Day/Night Band imagery with lightning strikes at 0842 UTC on 6 October 2014</strong> (click to animate)

Suomi NPP VIIRS Day/Night Band (0.70 µm), Infrared Imagery (11.45 µm) and Day/Night Band imagery with lightning strikes at 0842 UTC on 6 October 2014 (click to animate)

The Suomi NPP VIIRS image toggle, above, from the pre-dawn hours (3:42 am local time) on 6 October 2014 shows a 0.7 µm Day/Night Band image and an 11.45 µm Infrared image, along with observations of postive and negative lightning strikes. With ample illumination by moonlight, the “visible image at night” Day/Night Band image highlighted areas of convective overshooting tops, but also included bright horizontal stripes that are associated with intense lightning activity; after scanning a particularly bright area of lightning in Arkansas, this image also showed a darker “post-saturation recovery” stripe downscan (to the southeast), which stretched from central Arkansas into Mississippi. This vigorous convective system dropped southeastward from Oklahoma towards the Gulf of Mexico, eventually becoming a Quasi-Linear Convective System (QLCS) which produced hail and wind damage (with one fatality) across parts of northeastern Texas and far northwestern Louisiana (SPC storm reports).

GOES Sounder DPI Lifted Index (click to animate)

GOES Sounder DPI Lifted Index (click to animate)

The southward-dropping Mesoscale Convective System followed a channel of unstable air as diagnosed by the GOES Sounder, above. Note that the Lifted Index values were smaller (less instability) along the path that the system had moved. Total Precipitable water was also enhanced in that corridor, suggesting a region where moisture return from the Gulf of Mexico was ongoing and concentrated.

GOES Infrared Imagery(10.7 µm) at 1600 UTC, and Pilot Reports of Turbulence (click to enlarge)

GOES Infrared Imagery (10.7 µm) at 1600 UTC, and Pilot Reports of Turbulence (click to enlarge)

Mesoscale Convective Systems can exhibit signatures that suggest the presence of turbulence in the atmosphere. In the GOES-13 IR image above, parallel filaments or “transverse bands” of cirrus  (extending approximately north-south) on the poleward side of the MCS suggest the presence of turbulence, and scattered pilot reports of Moderate Turbulence confirm that. Visible MODIS Imagery, below, also shows the transverse bands, as well as the outflow boundary arcing from Houston to the northwest and north.

Terra MODIS visible imagery (0.65 µm) at 1705 UTC  (click to enlarge)

Terra MODIS visible imagery (0.65 µm) at 1705 UTC (click to enlarge)

An animation of hourly GOES-13 Visible imagery, below, shows the motion of the western portion of the outflow boundary as the decaying QLCS moved into the Gulf of Mexico.

GOES-13 Visible (0.65µm) imagery (click to animate)

GOES-13 Visible (0.65µm) imagery (click to animate)

GOES-13 6.5 µm water vapor channel imagery, below, displayed a signature of subsidence immediately upstream of the dissipating MCS, in the form of an arc of warmer/drier (yellow to orange color enhancement) brightness temperatures that extended from the Texas coast into central Arkansas. One rapidly-developing convective cell which formed along the advancing outflow boundary was responsible for severe turbulence in eastern Texas; the subtle signal of the westward-propagating outflow boundary could also be followed on the water vapor imagery.

<strong>GOES-13 6.5 µm water vapor channel images, with pilot reports of turbulence</strong> (click to play animation)

GOES-13 6.5 µm water vapor channel images, with pilot reports of turbulence (click to play animation)

Re-suspended volcanic ash from the Novarupta volcano in Alaska

September 29th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the hazy signature of a plume of re-suspended volcanic ash originating from the region of the Novarupta volcano in Alaska, moving southeastward over the Shelikof Strait toward Kodiak Island on 29 September 2014. The 1912 eruption of Novarupta left a very deep deposit of volcanic ash, which often gets lofted by strong winds in the early Autumn months before snowfall covers the ash (another example occurred on 22 September 2013). Surface winds gusted as high as 30 knots at regional reporting stations, with numerical models estimating terrain-enhanced winds as high as 40-50 knots over the Novarupta ash field.

An AWIPS II image of POES AVHRR 0.86 µm visible channel data (below) showed the ash plume at 22:46 UTC; a pilot report at 22:45 UTC indicated that the top of the ash plume was between 4000 and 6000 feet above ground level.

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

POES AVHRR 0.86 µm visible channel image, with METAR surface reports and Pilot reports (PIREPs)

A sequence of 3 Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (below) indicated that the re-suspended ash plume had been increasing in areal extent during that period.

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

Suomi NPP VIIRS true-color images from 27, 28, and 29 September

A sequence of 4-panel products from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) shows False-color images, Ash/dust cloud height, Ash/dust particle effective radius, and Ash/dust loading (derived from either Terra/Aqua MODIS or Suomi NPP VIIRS data).

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

4-panel MODIS/VIIRS products: False color image; Ash/dust cloud height; Ash/dust particle effective radius; Ash/dust loading

Hat tip to Mark Ruminski (NOAA/NESDIS) for alerting us to this event.