Lee-side cold frontal gravity wave

October 22nd, 2008 |
GOES-12 6.5 µm water vapor images

GOES-12 6.5 µm water vapor images

AWIPS images of the 4-km resolution GOES-12 6.5 µm water vapor channel (above) showed a southward-propagating  lee-side cold frontal gravity wave over New Mexico and Texas on 22 October 2008. This gravity wave was caused by a surface-based cold frontal boundary that was moving southward across the region.

MODIS 6.7 µm water vapor image + fog/stratus product image

MODIS 6.7 µm water vapor image + fog/stratus product image

A comparison of the 1-km resolution MODIS 6.7 µm water vapor channel and the MODIS fog/stratus product (above) indicated that there were narrow cloud bands along the leading edge of the frontal boundary / gravity wave, as well as more extensive patches of fog and/or stratus behind the front in the Texas panhandle.The MODIS Land Surface Temperature (LST) product (below) depicted LST values dropping into the 40s F (green colors) behind the front, with much warmer LST values in the 50s and 60s F (yellow to orange colors) ahead of the front.

MODIS 6.7 µm water vapor channel + Land Surface Temperature product

MODIS 6.7 µm water vapor channel + Land Surface Temperature product

NOAA wind profiler data from Jayton, Texas (below) showed the deepening of the cold northerly flow after the cold front moved through the area — the top of the cold air appeared to be close to the 700 hPa level (around 10,000 feet above ground level).

Jayton, Texas NOAA wind profiler data

Jayton, Texas NOAA wind profiler data

GOES-12 water vapor channel weighting functions calculated for the rawinsonde profiles at Amarillo, Texas (below) demonstrated a significant lowering of the layer being detected by the water vapor channel in the 12 hours between 00 and 12 UTC on 22 October. With the drier air mass in place at 12 UTC, the GOES-12 water vapor channel was able to detect a substantial amount of energy originating from within the 500-700 hPa layer, allowing the signature of the frontal gravity wave to appear on the GOES-12 water vapor imagery. The wave structure was better-defined on the MODIS water vapor image, due to the improved spatial resolution and the more direct satellite viewing angle.

GOES-12 water vapor channel weighting functions for Amarillo TX

GOES-12 water vapor channel weighting functions for Amarillo TX