EUMETSAT Meteosat-10 6.25 µm water vapor channel images (click to play animation)

A band of strong westerly/northwesterly winds moved across northern Scotland and southern Norway on 02 January 2015 (surface analyses), with a number of locations reporting wind gusts in excess of 50-60 knots. The highest wind gust seen was 64 knots at the Gullfax Platform (ENGC) in the North Sea at 16 UTC, with a wind gust to 63 knots at Oslo Fornebu airport (ENFB) at 21 UTC; in the morning hours, an aircraft was blown off the runway at Stornoway Airport, Isle of Lewis, in the Outer Hebrides of Scotland (EGPO). Ferry services between Kristiansand and Denmark as well as those between Sandefjord and Sweden were cancelled due to the strong winds. EUMETSAT Meteosat-10 6.25 µm water vapor channel images (above; click image to play animation; also available as an MP4 movie file) showed that most of the stronger wind gusts occurred beneath a ribbon of drier air aloft, in which instability rain/snow showers (and even thunderstorms) were developing.

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image at 10:57 UTC visualized using the SSEC RealEarth web map server (below) showed a more detailed view of the instability showers and thunderstorms as they were developing over the North Sea. Along the west coast of Norway, thunderstorms were reported at Haugesund, Ålesund, Florø, and Bergen.

Suomi NPP VIIRS true-color image

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Aqua MODIS 0.65 µm visible channel image and False-color Red/Green/Blue (RGB) images

A cold storm system moving through the Southwest US on 31 December 2014 produced significant snowfall in many of the higher-elevation mountain ranges of California, Baja California, Nevada, and Arizona (up to 20 inches at Mountainaire AZ), but also left lighter amounts of snowfall at some low-elevation locations of the eastern Mojave Desert where snowfall is considered to be quite rare (NWS Las Vegas Public Information Statement) | Event  Summary). This event marked the first time that snowfall had been recorded during the month of December at Needles, California.

As clouds began to clear over the region on the following day (01 January 2015), areas which still had snow on the ground could be seen using satellite imagery. On a comparison of Aqua MODIS 0.65 µm visible channel and false-color Red/Green/Blue (RGB) images at 20:33 UTC or 1:33 PM local time (above), snow cover that appeared as shades of white on the visible image also appeared as darker shades of red on the RGB image.

As the day progressed, the sun had the effect of melting the lighter amounts of snow cover, as seen on GOES-15 (GOES-West) 0.63 µm visible channel images (below; click image to play animation). However, due to the presence of the unusually cold air mass, new records for coldest 01 January daily maximum temperature were set for Phoenix (46ºF) and Tucson (41ºF).

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

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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 (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)

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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)

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

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

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

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)

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)

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

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

According to the National Operational Hydrologic Remote Sensing Center, only 35.5% of the Lower 48 states had snow cover on 25 December 2014. However, a deep cutoff low over the Hawaiian Islands had brought unusually cold air aloft (the 500 hPa temperature on the Lihue rawinsonde report was as cold as -18º C, which is extremely cold by Hawaiian standards) and strong winds, which prompted Blizzard Warnings to be issued for the high elevation summits of the Big Island of Hawai’i on 23-24 December. As the cutoff low departed and skies began to clear, GOES-15 (GOES-West) 0.63 µm visible channel images (above; click image to play animation) revealed the bright white snow-covered summits of Mauna Kea and Mauna Loa on Christmas Day.

A toggle between a Suomi NPP VIIRS 0.64 µm visible channel and a false-color Red/Green/Blue (RGB) “snow vs cloud discrimination” image at 23:22 UTC (below) confirmed that the bright white features seen in the GOES-15 visible images was indeed snow cover — snow (and fully-glaciated ice clouds) appear as darker shades of red on the RGB image. Cloud tops that are partially glaciated appear as lighter shades of pink.

Suomi NPP VIIRS 0.64 µm visible channel and false-color “snow vs cloud discrimination” RGB images

===== 26 December Update =====

Using the SSEC RealEarth web map server, the comparison below shows 375-meter resolution Suomi NPP VIIRS true-color RGB images of the Big Island of Hawai’i on 20 December (before the snowfall on the Mauna Kea and Mauna Loa summits) and also on 25-26 December (after the snowfall). On the 26 December image, you can see that the patches of snow had melted somewhat at the 2 summits; in addition, an increase in hazy volcanic fog (vog) can be seen drifting southeastward off the island; this vog was being generated by the ongoing eruption of the Kilauwea volcano in the Hawai’i Volcanoes National Park.

Suomi NPP VIIRS true-color RGB images

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