Reno, Nevada radar dome failure

December 19th, 2008 |
GOES-13 6.5 µm water vapor images

GOES-13 6.5 µm water vapor images

Strong winds gusting to around 140 mph (63 m s-1) caused damage to the Reno/Virginia Peak radar in western Nevada at around 10:30 UTC on 19 December 2008. GOES-13 images of the 4-km resolution 6.5 µm “water vapor channel” (above) revealed a large area of “lee waves” immediately downwind of the Sierra Nevada Range — intense vertical motions associated with these lee waves were producing strong bands of subsidence (indicated by the darker blue to yellow color enhancement on the water vapor imagery), which were likely  contributing to the strong wind gusts at the surface.

The National Weather Service forecast office at Reno captured an AWIPS image of the 1-km resolution MODIS 6.7 µm water vapor channel (below) about 4 hours prior to the time of the radar damage. Reno is one of the NWS forecast offices that receives the MODIS product suite that CIMSS distributes in AWIPS format.

MODIS 6.7 µm water vapor iamge (courtesy of NWS Reno, Nevada)

MODIS 6.7 µm water vapor image (courtesy of NWS Reno, Nevada)

The photos below (from the National Weather Service forecast office at Reno) show the damage suffered by the radome that encloses the radar antenna.

Photos of wind-damaged radome (courtesy of NWS Reno, Nevada)

Photos of wind-damaged radome (courtesy of NWS Reno, Nevada)

— 25 DECEMBER UPDATE —

Another round of strong winds brought gusts to 95 mph on 25 December 2008, which caused even more damage to the radome and the actual radar antenna structure. GOES-13 water vapor images (below) again showed the presence of lee waves in the region for several hours prior to the period of the peak winds (which occurred around 10:15 UTC) — however, the arrival of dense cirrus clouds eventually masked the lee wave signature around the time of the additional radar damage.

GOES-13 6.5 µm water vapor images

GOES-13 6.5 µm water vapor images

Snow in the Desert Southwest

December 18th, 2008 |
GOES-13 6.5 µm water vapor images (with surface weather reports)

GOES-13 6.5 µm water vapor images (with surface weather)

A significant snowfall event occurred over the Desert Southwest region of the US on 17 December 2008 — as much as 30.0 inches of snow was reported at Wrightwood in the mountains of southern California (just northeast of Los Angeles), and Las Vegas, Nevada received 3.6 inches (setting a new record for the most snowfall during any December). Malibu Hills, California even received 0.5 inch of snow (at the 2000-foot level). GOES-13 6.5 µm water vapor imagery (above) showed the large and intense storm as is moved inland — note the appearance of convective elements that developed over parts of California, Arizona, and Nevada (along the leading edge of the dry slot). In addition, wave patterns downwind of Guadalupe Island and northern Baja California indicated the presence of very strong winds. These wave patterns were clearer on the 4-km resolution GOES-13 water vapor channel, compared to the 8-km resolution water vapor channel on GOES-11. Note that GOES-13 had recently replaced GOES-12 as the operational GOES East satellite.

An AWIPS image of the MODIS 6.7 µm water vapor channel with an overlay of MADIS water vapor winds (below) revealed that wind speeds aloft were as strong as 78 knots at the 387 hPa level, just ahead of the advancing dry slot. The GOES-11 Sounder Total Column Ozone product also showed a well-defined lobe of elevated ozone levels (in the 350-400 Dobson Unit range) associated with the developing storm.

MODIS 6.7 µm water vapor image + MADIS water vapor winds

MODIS 6.7 µm water vapor image + MADIS water vapor winds

Another interesting feature seen on the water vapor imagery was an elongated band of cloudiness that developed along a very pronounced deformation zone that formed over Nevada and Utah — there were a few pilot reports of moderate turbulence in the vicinity of this deformation zone (below), with one report of moderate to severe turbulence over central Nevada at 00:44 UTC (at the 33,000-foot flight level).

GOES water vapor images + pilot reports of turbulence

GOES water vapor images + pilot reports of turbulence

AWIPS images of the 1-km resolution MODIS water vapor, IR, and visible channels (below) showed a clearer view of the convective elements that were developing along the leading edge of the dry slot. These convective elements likely enhanced local precipitation rates as they moved across the region.

MODIS 6.7 µm water vapor, 11.0 µm IR, and visible channel

MODIS 6.7 µm water vapor, 11.0 µm IR, and visible channel

GOES-13 visible images on the following day (18 December, below) showed that extensive snow cover remained across much of the Desert Southwest, while some parts of the snow cover were seen to melt during the daytime hours. In extreme southern Nevada, note that there appeared to be very little snow on the ground in the northern portion of the Las Vegas Valley — Nellis Air Force Base in North Las Vegas (station identifier KLSV) and McCarran International Airport (station identifier KLAS) looked to be relatively snow-free, while Henderson (KHND) located just to the southeast still had enough snow on the ground to appear brighter white on the visible imagery. Up to 8 inches of snow accumulation was reported in the Henderson area — the Henderson Airport reported moderate snow for a time, with surface visibility reduce to 1/4 mile.

GOES-13 visible images

GOES-13 visible images

A comparison of AWIPS images of the MODIS visible and the near-IR “snow/ice” channel (below) confirms the presence of and the areal coverage of snow cover — snow and ice (along with water in oceans and lakes) are strong absorbers at the 2.1 µm wavelength, so they appear as darker features on the “snow/ice” image (in contrast to supercooled water droplet  clouds, which appear as brighter white features). Note the even darker appearance on the MODIS snow/ice image in the Henderson area (just southeast of KLAS), where higher amounts of snow fell. A darker signal is also apparent on the snow/ice image in the Barstow-Dagget (KDAG) and Edwards Air Force Base (KEDW) areas — the center of the storm circulation moved directly over that particular region, which may have helped to enhance local precipitation rates.

MODIS visible and near-IR snow/ice channel images

MODIS visible and near-IR "snow/ice" channel images

19 December Update: 250-meter resolution MODIS true color and false color imagery from the SSEC MODIS Today site (below) showed a stunning view of the area from Las Vegas, Nevada…to Lake Mead/Lake Mojave along the Nevada/Arizona border…to the Grand Canyon in Arizona, where significant snow cover still remained in many areas.

MODIS true color and false color images

MODIS true color and false color images

“Lake-effect clouds” in Montana and North Dakota

December 16th, 2008 |
MODIS fog/stratus product and 11.0 µm IR images

MODIS fog/stratus product and 11.0 µm IR images

Even though very cold arctic air had invaded much of the north-central US  (minimum temperatures on the morning of 15 December were -33º F at Havre, Montana and -28º F at Bottineau, North Dakota), the deeper man-made lakes (created by dams) along the Missouri River remained unfrozen on 16 December 2008. AWIPS images of the MODIS fog/stratus product and the 11.0 µm IR window (above) revealed long plumes of supercooled water droplet clouds (MODIS Cloud Phase product) streaming eastward from the relatively warm lakes — the cloud plumes were enhanced with yellow to orange colors on the fog/stratus product image, and the warm lakes were enhanced with yellow to orange colors on the IR window image.

GOES-12 10.7 µm IR images (below) showed the evolution of these “lake-effect cloud plumes” during the night-time and early morning hours on 16 December. While winds at the surface were fairly light, the winds higher aloft (at the 925 hPa or 3000 ft level) were advecting the cloud material eastward.

GOES-12 10.7 µm IR images

GOES-12 10.7 µm IR images

250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) imagery from the SSEC MODIS Today site (below) showed a closer view of Fort Peck Lake in northeastern Montana and Lake Sakakawea in western North Dakota on the previous day (15 December). Small plumes of  lake-effect clouds could be seen beginning to stream southeastward off the unfrozen lakes at that time — these supercooled water droplet clouds exhibited a brighter white appearance on the false color images, in contrast to the cyan snow-covered ground.

MODIS true color and false color images

MODIS true color and false color images (Fort Peck Lake, Montana)

MODIS true color and false color images (Lake Sacajawea)

MODIS true color and false color images (Lake Sakakawea, North Dakota)

GOES-12 outage…GOES-13 to the rescue!

December 15th, 2008 |
AWIPS 4-panel of GOES imagery

AWIPS 4-panel GOES imagery (IR, visible, water vapor channels)

The GOES-12 satellite (the operational GOES-East satellite) suffered a Thruster 2B oxidizer leak around 22:00 UTC on 14 December 2008, which caused the suspension of GOES-12 Imager and Sounder data. For several hours following the GOES-12 thruster anomaly, GOES-11 (the operational GOES-West satellite) was placed into Full-Disk mode to provide coverage as far east as possible. AWIPS 4-panel GOES images (above) show that the image quality was adversely impacted over the far eastern US and Canada during that time, due to the very large viewing angle from GOES-11 (which is positioned at 135º W longitude). Also, note that the water vapor channel imagery (lower right panel) was not available in AWIPS during the time that GOES-11 IR imagery (upper 2 panels) was filling in for the missing GOES-12 data — and of course, there was no visible channel data (lower left panel) since it was night-time.

However, the GOES-13 satellite — which had been in an extended period of on-orbit storage at 105º W longitude — had been activated in early August of 2008, so it could very quickly be utilized to replace GOES-12. As of 12:30 UTC on 15 December, GOES-13 data began to replace GOES-12 data as the GOES-East satellite data source for AWIPS, which then allowed  the image quality over the far eastern US and Canada to return to normal. The channels on the GOES-13 Imager and Sounder are identical to those on GOES-12 (including the 4-km resolution water vapor channel) — however, the primary improvements with GOES-13 are better image navigation, and larger on-board batteries to allow the satellite to operation through Spring and Fall eclipse periods (when the satellite is in the Earth’s shadow, and the solar panels cannot provide power to the spacecraft instruments).

For the latest information, see the NOAA Satellite Services Division Special Bulletins.

Note: GOES-13 data is being re-broadcast through GOES-12, so users with GOES East direct broadcast ground stations do not need to adjust their antennas.