Hole punch clouds and aircraft distrails over Georgia and South Carolina

February 17th, 2012 |
GOES-13 0.63 µm visible channel images

GOES-13 0.63 µm visible channel images

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above) showed that there were a number of “hole punch clouds” and long “aircraft dissipation trails” (or “distrails”) drifting east-northeastward over eastern Georgia and the northern half of South Carolina on 17 February 2012. These features occur when aircraft ascend or descend through a cloud layer composed of supercooled water droplets — particles from the jet engine exhaust act as ice nuclei that initiate glaciation. The resulting relatively large ice crystals then begin to fall out of the supercooled water droplet cloud layer, causing the hole punch or aircraft dissipation trail to appear.

A closer view using a 250-meter resolution Terra MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) shows more structural details of some of the hole punch and distrail features at 15:47 UTC (10:47 am local time). The aircraft likely penetrated the supercooled water droplet cloud over Georgia, after which the hole punch and distrail signatures grew as the cloud drifted east-northeastwrad over South Carolina.

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

MODIS true color Red/Green/Blue (RGB) image (viewed using Google Earth)

A comparison of 250-meter resolution Terra MODIS true-color and false-color Red/Green/Blue (RGB) images (below) helps to verify that the hole punch and distrail features were indeed composed of ice crystals (which appear as cyan on the false-color image, in contrast to the brighter white supercooled water droplet cloud features).

MODIS true-color and false-color Red/Green/Blue (RGB) images

MODIS true-color and false-color Red/Green/Blue (RGB) images

Fog and low clouds over the Ohio River Valley region

February 17th, 2012 |
GOES-13 fog/stratus product (click image to play animation)

GOES-13 fog/stratus product (click image to play animation)

AWIPS images of the GOES-13 fog/stratus product (above; click image to play animation) did not do a particularly good job of depicting a well-defined signal of the fog/stratus that was in place across parts of the Ohio River Valley region on 17 February 2012. Note that a number of stations were reporting night-time fog and/or freezing fog in parts of far eastern Missouri, southern Illinois and Indiana, and western Kentucky.

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

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

Even with the improved 1-km resolution of the MODIS fog/stratus product, no good signal was displayed at 03:40 UTC  (above) or at 07:52 UTC (below) over the areas that were reporting fog/freezing fog.

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

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

As part of CIMSS participation in GOES-R Proving Ground activities, new satellite products are being developed and tested — and one such product is an Instrument Flight Rules (IFR) Probability product (below; click image to play animation). This IFR Probability product blends satellite data and model fields to display regions where the cloud ceiling is likely to be between 500 and 1000 feet. The IFR Probability product did a much better job at highlighting the relatively large area where IFR cloud ceiling conditions were present at a number of reporting stations (some of which were experiencing cloud ceilings of 100 to 200 feet, along with freezing fog limiting the visibility to 0.3 miles at times) — for example: Effingham IL (K1H2) / Mount Vernon IL (KMVN) / Harrisburg IL (KHSB) / Lawrenceville IL (KLWV) / Bloomington IN (KBMG) / Cape Girardeau MO (KGCI) / Pahducah KY (KPAH).

GOES-13 IFR Probability product (click image to play animation)

GOES-13 IFR Probability product (click image to play animation)

GOES-13 0.63 µm visible channel images (below; click image to play animation) showed the areas of fog/stratus burning off quickly after sunrise — and the fog/stratus appeared to be relatively shallow in nature. The fact that the fog/stratus did not appear to be very thick may have been a factor that limited detection by the traditional GOES-13 (10.7-3.9 µm) and MODIS (11-3.7 µm) fog/stratus products.

GOES-13 0.63 µm visible channel image (click image to play animation)

GOES-13 0.63 µm visible channel image (click image to play animation)