GOES-15 6.5 µm water vapor channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed an intense upper level shortwave trough of low pressure moving northeastward across southcentral and eastern Alaska on 18 December 2011. Strong southerly flow associated with this system brought unseasonably warm air into the region, with Anchorage (station identifier PANC) reaching a daily maximum temperature of 45º F (one degree F shy of their record high for the date), and Big Delta (station identifier PABI) tied their daily record high of 37º F. Strong winds were also experienced with this disturbance, with surface winds gusting in excess of 100 mph in southcentral Alaska. It is also interesting to note the development of a small westward-propagating “wave feature” at the end of the water vapor animation near Tanana (station identifier PATA).

Over eastern Alaska the water vapor images also showed a large orographic “banner cloud” that formed downwind of the high terrain of the Alaska Range. A closer look at this banner cloud feature can be seen using an AWIPS image of 1-km resolution MODIS 11.0 µm IR channel data with an overlay of GFS model 500 hPa winds (below). The coldest MODIS IR brightness temperatures along the leading edge of the banner cloud were -65º C, which was just a few degrees colder than the tropopause temperature on the 12:00 UTC Anchorage rawinsonde data. The winds aloft then turned anticyclonically, carrying some of the banner cloud materail eastward into the Yukon Territory of Canada.

MODIS 11.0 µm IR image + GFS 500 hPa winds

The corresponding 1-km resolution MODIS Cloud Type product (below) indicated that much of this banner cloud was of the “opaque ice” category (yellow color enhancement).

MODIS Cloud Type product

The 1-km resolution POES AVHRR Cloud Top Height product (below) indicated that the highest portions of the banner cloud feature were in the 10-11 km range.

POES AVHRR Cloud Top Height product

As an interesting aside, a Boeing 747 flying just off the coast of Alaska encountered severe turbulence at a flight level of 35,000 feet — the captain of the aircraft “said this was the first time he has ever reported severe turbulence” (below).

POES AVHRR 12.0 µm IR image with pilot reports of turbulence

Note on the GOES-15 water vapor images shown above that this area was near the leading edge of an advancing dry slot — and 1-km resolution GOES-15 0.63 µm visible channel images (below) depicted a few cloud features resembling banded convective cells along the trailing edge of the cloudiness just ahead of the dry slot. These convective bands (or the strong deformation axis seen developing on the water vapor imagery) may have been responsible for producing high-altitude turbulence across that region.

GOES-15 0.63 µm visible channel images

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MTSAT-1R 10.8 µm IR images (click image to play animation)

MTSAT-1R 10.8 µm IR images from the CIMSS Tropical Cyclones site (above; click image to play animation) showed a fairly compact cluster of cold convective cloud tops associated with Tropical Storm Washi as it moved westward toward the Philippines during the 15-16 December 2011 period.

A closer view using MIMIC microwave imagery (below) also showed a relatively small area of enhanced brightness temperatures (representing heavy precipitation) crossing Mindanao Island in the southern Philippines on 16 December.

MIMIC microwave imagery

However, AWIPS images of the MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) revealed that Tropical Storm Washi was embedded within a long fetch of very rich tropical moisture, with TPW values in excess of 60 mm or 2.4 inches (darker red color enhancement). This abundance of moisture helped to fuel over 10 hours of heavy rainfall, which resulted in widespread flash flooding and reports of over 900 deaths in the Philippines.

MIMIC Total Precipitable Water product (click image to play animation)

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MODIS true color RGB image + MODIS false color RGB image

A comparison of a MODIS true color Red/Green/Blue (RGB) image with the corresponding MODIS false color RGB image of Hudson Bay, Canada on 15 December 2011 (above) revealed the following: (1) most of the northern and western portions of Hudson Bay were ice-covered (the ice appeared bright white on the true color image, and darker shades of red on the false color image) and (2) thee false color image made it easier to discriminate between the ice (darker red) and a diverging pattern of supercooled water cloud streets (white to cyan colored features) which were aligned in the direction of strong boundary layer winds in the wake of a cold frontal passage. The horizontal convective rolls that created these cloud streets may have also contained significant amounts of blowing snow.

AWIPS images of MODIS false color RGB images with overlays of METAR surface reports (below) showed that winds were gusting as high as 33 to 38 knots at stations along the western edge of Hudson Bay.

MODIS Red/Green/Blue (RGB) false color images

McIDAS images of GOES-13 0.63 µm visible channel data (below) showed that the strong winds were acting to move large portions of the ice, which according to the Canadian Ice Service was still fairly young “gray” (5-15 cm thick) to “gray-white” (15-30 cm thick) ice.

GOES-13 0.63 µm visible channel images

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1-km resolution MODIS vs 4-km resolution GOES-13 fog/stratus product images

The National Weather Service forecast office in Mobile, Alabama mentoned their use of the MODIS fog/stratus product during the pre-dawn hours on 14 December 2011:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
1140 PM CST TUE DEC 13 2011

.AVIATION UPDATE (14/06Z ISSUANCE)…LOW CIG AND VSBY CONDITIONS CONTINUE. GOES IMAGER 11-3.9 AND MODIS POLAR ORBITER CONTINUE TO INDICATE A LOW STRATUS DECK WITH LOW VISIBILITY IN A LAYER WHOSE EDGE OVERLAYS A LINE FROM NEAR FOLEY TO BAY MINETTE AND ON UP TO CAMDEN. POINTS WEST OF SAID LINE ARE PRETTY WELL SOCKED IN AND PRETTY CLEAR ELSEWHERE. HAVE THEREFORE KEPT REDUCED PREVAILING GROUP TO A QUARTER MILE AND VV001 FOR BFM AND MOB.

A comparison of AWIPS images of the 1-km resolution MODIS vs the corresponding 4-km resolution GOES-13 fog/stratus product (above) demonstrated the advantage of using higher spatial resolution data to more accurately locate the eastern edge of the fog.

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