Interesting wave features near Guadalupe Island

February 24th, 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)

Hat-tip to Matt Sitkowski and Carl Parker of The Weather Channel for the heads-up on some interesting wave features that could be seen in the vicinity of Guadalupe Island on McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) on 24 February 2014. Apparently a gravity wave had propagated northwestward through the region during the morning hours, perturbing the depth of the marine boundary layer (MBL) such that undulations in the MBL stratocumulus clouds were quite evident. In addition, an unusual “dry pulse” propagated outward from Guadalupe Island (located in the center of the images). These wave features eventually became hidden as layers of middle and high clouds overspread the area from the southwest.

AWIPS images of GOES-15 0.63 µm visible channel data with overlays of Real-Time Mesoscale Analysis (RTMA) surface winds (below) showed that the surface flow was very light or even calm across much of the Guadalupe Island region during the time that the “dry pulse” was most evident on visible imagery.

GOES-15 0.63 µm visible images with RTMA surface winds

GOES-15 0.63 µm visible images with RTMA surface winds

Suomi NPP views of a strong midwest cyclone

February 21st, 2014 |
Suomi NPP VIIRS 1.38 µm near-infrared imagery (M09), 1736 UTC 21 February 2014 (click image to enlarge)

Suomi NPP VIIRS 1.38 µm near-infrared imagery (M09), 1736 UTC 21 February   2014 (click image to enlarge)

A strong late-winter cyclone brought significant snows and blizzard conditions to the upper Great Lakes/northern Plains on 21 February 2014 (NWS storm summaries: MPX | DLH | ARX). In the warm sector of the storm, there were numerous reports of tornadoes, large hail, and damaging winds in the eastern US. Suomi NPP viewed the storm multiple times, including just before 1800 UTC on 21 February.

The Suomi NPP VIIRS 1.38 µm imagery, above, was created using CSPP and highlights cirrus-level clouds, documenting just how widespread the canopy of this extratropical cyclone was (more imagery is available via ftp, and a description of the various bands is available here).

Suomi NPP VIIRS I1, Day/Night, I3, I4, I5 bands at 1736 UTC 21 February 2014 (click image to enlarge)

Suomi NPP VIIRS I1, Day/Night, I3, I4, I5 bands at 1736 UTC 21 February 2014 (click image to enlarge)

VIIRS imagery (375-meter resolution I-bands 1, 3, 4, and 5, along with the 750-meter resolution Day/Night Band) is available in AWIPS via an LDM subscription. The animation above cycles through these different bands as displayed using AWIPS: Visible (0.64 µm), Day/Night Band (0.70 µm), Snow/Ice Channel (1.61 µm), Shortwave IR (3.74 µm) and IR Window (11.45 µm) channels.

VIIRS 750-meter resolution M-bands can be used to create true-color imagery: the example from 1736 UTC is shown below.

Suomi NPP VIIRS True-color imagery, 1736 UTC 21 February 2014 (click image to enlarge)

Suomi NPP VIIRS True-color imagery, 1736 UTC 21 February 2014 (click image to enlarge)

GOES-13 Navigation anomalies due to a maneuver

February 19th, 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)

A GOES-13 (GOES-East) North/South Station Keeping maneuver was performed on Wednesday, February 19, 2014, beginning 1145 UTC, and ending at 1945 UTC (Link). During this time, the navigation of the satellite degraded mostly in the north-south direction. At 1945 UTC, after the maneuver ended, the navigation snapped back to normal. (Compare the 1932 and 1945 UTC images).

Navigation error tracking is available online for some geostationary satellites. For example, this link, off this page, shows landmark errors from MTSAT. NOAA’s OSPO maintains a site for GOES satellites; however, results are posted weekly. (Link).

Severe turbulence over Wyoming

February 17th, 2014 |
MODIS 6.7 µm water vapor channel image, with pilot reports of turbulence

MODIS 6.7 µm water vapor channel image, with pilot reports of turbulence

United Airlines flight 1676 enroute from Denver, Colorado KDEN to Billings, Montana KBIL (flight track) encountered severe turbulence at an altitude of 34,000 feet over Wyoming on 17 February 2014. Three crew members and two passengers were injured, and taken to hospitals upon landing in Billings. An AWIPS image of 1-km resolution Aqua MODIS 6.7 µm water vapor channel data (above) showed a number of pilot reports of moderate turbuence over Wyoming between the altitudes of 33,000 and 45,000 feet around that time; the United 1676 pilot report of severe turbulence is highlighted in red.

On the MODIS water vapor image, note the appearance of distinct signatures of non-parallel mountain waves just to the east of that turbulence plot (in the vicinity of KIDV) — these closely-spaced bands of descending dry air (darker blue to yellow color enhancement) and ascending moist air (lighter blue to pale white color enhancement) were just east (downwind) of the Bighorn Mountains. The corresponding MODIS 0.65 µm visible channel and 11.0 µm IR channel images (below) showed that there were no cloud features associated with the entire extent of these mountain waves — they were were essentially occurring in “clear air”. This example demonstrates the value of high spatial resolution water vapor imagery for helping to identify signatures of potential clear air turbulence.

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images

An animation of 4-km resolution GOES-13 6.5 µm water vapor channel images (below; click image to play animation) showed that there were numerous other reports of moderate and even severe turbulence over Wyoming between about 20:00 UTC and 23:40 UTC. On the final 23:40 UTC image, there was a pilot report of severe turbulence as high as 47,000 feet in that same general area. The mountain wave signature to the lee of the Bighorn Mountains was not stationary, but was seen to exhibit some meandering during that time period.

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

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