Did weather play a role in the crash of AirAsia Flight 8501?

December 27th, 2014
SSEC RealEarth fade between the regional map and the 23:00 UTC MTSAT-2 10.8 µm IR image

SSEC RealEarth fade between the regional map and the 23:00 UTC MTSAT-2 10.8 µm IR image

During the northwestward flight of AirAsia 8501 from Surabaya, Indonesia to Singapore, contact was lost with the aircraft over the Java Sea (likely east of the island of Pulau Belitung) on 28 December 2014 (late 27 December UTC time). Using the SSEC RealEarth web map server site, a fade between the regional map and the MTSAT-2 10.8 µm IR image at 23:00 UTC is shown above. The satellite image revealed that there were clusters of deep convection (thunderstorms with very high, very cold cloud tops) over the middle portion of the flight path.

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

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

COMS-1 10.8 µm IR channel images (above; click to play animation; also available as an MP4 movie file) indicated that the coldest cloud-top IR brightness temperatures were in the -80º to -85ºC range (violet color enhancement) with these thunderstorms. The location of Surabaya, Indonesia (station identifier WARR) and Singapore (station identifier WSSS) are annotated on the images; the last point of contact (at 23:24 UTC) was approximately within the circle drawn just to the left of the center of the images, when the aircraft was flying at an altitude of 32,000 feet (9.75 km) over the Java Sea. There were reports from various media sources that the pilots had requested to divert their flight path and climb to a higher altitude to avoid adverse weather conditions not long before contact was lost.

The corresponding COMS-1 0.675 µm visible channel images (below; click to play animation; also available as an MP4 movie file) showed evidence that there were some overshooting tops associated with these thunderstorms.

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

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

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MTSAT-2 10.8 µm IR channel image (click to enlarge)

MTSAT-2 10.8 µm IR channel image (click to enlarge)

Given that there was a long gap in available COMS-1 images (between 23:00 and 23:45 UTC), a closer view is shown using the 23:32 UTC MTSAT-2 10.8 µm IR channel (above) and 0.675 µm visible channel images (below). A circle is again drawn near the center of the MTSAT-2 images to denote the approximate location of final radar contact with the aircraft at 23:24 UTC — and the intended final destination of Singapore (WSSS) is labelled in the upper left corner of the images. Similar to what was seen in the COMS-1 images, the coldest cloud-top IR brightness temperature in the area at that time was -81.4ºC, and there was evidence of overshooting tops in the near vicinity on the visible image. (Note: due to the far southern location just below the Equator, the flight region on the 22:00 COMS-1 image was actually being scanned around 22:07 UTC, while on the 22:32 UTC MTSAT-2 image the flight region was being scanned around 22:39 UTC).

MTSAT-2 0.675 µm visible channel image (click to enlarge)

MTSAT-2 0.675 µm visible channel image (click to enlarge)

A nearby rawinsonde report from Pangkalpinang (station identifier 96237 on the MTSAT-2 images) showed that the aircraft cruising flight level of 32,000 feet was near 300 hPa (9750 meters above ground level), where the air temperature was -29.3ºC and winds were from the west-southwest at 16 knots (below). The tropopause appeared to be around 100 hPa (at a height of 54,265 feet or 1654 km), with an air temperature of -86.5ºC — close to the coldest cloud-top IR brightness temperatures seen on the COMS-1 and MTSAT-2 IR images. Moisture was abundant throughout the atmospheric column, with a Total Precipitable Water value of 52.4 mm or 2.1 inches.

Pangkalpinang, Indonesia rawinsonde report

Pangkalpinang, Indonesia rawinsonde report

MTSAT-2 water vapor image derived atmospheric motion vectors from the CIMSS Tropical Cyclones site (below) showed that upper-tropospheric winds over the flight region (located at the far top center portion of the images) before, during, and after the flight time were generally southwesterly to westerly in the 15-30 knot range.

MTSAT-2 6.57 µm water vapor channel images with upper-tropospheric atmospheric motion vectors

MTSAT-2 6.57 µm water vapor channel images with upper-tropospheric atmospheric motion vectors

Deep convection is not uncommon in this region during this time of the year, when the Intertropical Convergence Zone (ITCZ) migrates southward during the Southern Hemisphere summer season. The presence of warm sea surface temperatures along with abundant Total Precipitable Water over western Indonesia (below) helps to create an environment that is favorable for the growth and maintenance of large thunderstorms.

Global image of Sea Surface Temperatures on 27 December

Global image of Sea Surface Temperatures on 27 December

25-27 December MIMIC Total Precipitable Water product (click to play animation)

25-27 December MIMIC Total Precipitable Water product (click to play animation)

For an additional detailed meteorological analysis of this event, see the Weather Graphics site.

===== 30 December Update =====

Map of AirAsia Flight 8501, and location of initial debris (credit: New York Times)

Map of AirAsia Flight 8501, and location of initial debris (credit: New York Times)

On the third day of the search, aircraft debris and bodies of passengers were discovered about 66 miles southwest of the last known coordinates of AirAsia Flight 8501 (above). The prevailing ocean current in the Java Sea (below) may have displaced some of the debris southwestward from the actual crash site.

Map of ocean currents (credit: Columbia University Earth Institute)

Map of ocean currents (credit: Columbia University Earth Institute)

The Indonesian Bureau of Meteorology, Climate, and Geophysics (BMKG) released their meteorological analysis of the AirAsia 8501 crash on 31 December.

First images from Himawari-8

December 18th, 2014
Himawari-8 0.64 µm visible channel image (click to enlage)

Himawari-8 0.64 µm visible channel image (click to enlarge)

The Japan Meteorological Agency has released the first images from the AHI instrument on the Himawari-8 satellite, which was launched on 7 October this year.

This link shows full disk imagery from all 16 spectral bands. The AHI on Himawari-8 is very similar to the ABI that will fly on GOES-R.

A comparison of images using each of the 16 spectral bands is shown below, centered over the Sea of Japan. Cloud streets are seen over much of the open waters, due to the southeastward and eastward transport of very cold air from Siberia (surface analysis). Lee waves (or “mountain waves”) are evident on the water vapor bands (8, 9  and 10) downwind or southeast of the higher terrain areas on the main Japanese island of Honshu.

Comparison of the 16 AHI spectral bands, centered on the Sea of Japan (click to enlarge)

Comparison of the 16 AHI spectral bands, centered on the Sea of Japan (click to enlarge)

 Band 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
µm  0.47   0.52   0.64   0.86   1.6   2.3   3.9   6.2   6.9   7.3   8.6   9.6   10.4   11.2   12.4   13.3 

Similar comparisons of Himawari-8 images covering Hawaii, western Australia, and the far Southern Hemisphere are available on the First Light AHI Satellite Band Webapp.

As seen on the MTSAT-2 vs Himawari-8 comparison below, even at large satellite viewing angles over the far southern portion of the Southern Hemisphere (for example, between Australia/Tasmania and Antarctica) AHI imagery such as that from water vapor channels exhibits higher quality (due to factors such as improved spatial resolution, signal-to-noise ratio, data bit depth, etc).

MTSAT-2 vs Himawari-8 water vapor channel images

MTSAT-2 vs Himawari-8 water vapor channel images

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

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