A Foehn gap over California, and very strong jet stream winds over the Southwest US

March 31st, 2010 |
MODIS water vapor. IR, and visible images

MODIS water vapor. IR, and visible images

AWIPS images of the 1-km resolution MODIS 6.7 µm water vapor channel, the 11.0 µm IR channel, and the 0.65 µm visible channel (above) showed a pronounced “Foehn gap” immediately downwind of the highest terrain of the Sierra Nevada mountain range on 31 March 2010.

A comparison of the 1-k resolution MODIS 6.7 µm water vapor image with the corresponding 8-km resolution 6.7 µm water vapor image from GOES-11 (below) demonstrates the ability to detect such features with better spatial resolution.

1-km resolution MODIS and 8-km resolution GOES-11 water vapor images

1-km resolution MODIS and 8-km resolution GOES-11 water vapor images

Strong southwesterly winds aloft with speeds of 70-110 knots were creating this Foehn gap — but the core of a very strong jet stream was located a bit farther to the south and east. According to the RUC model, the highest wind speeds at the level of maximum Wind Speed was in excess of 140 knots over far northwestern Arizona and far southwestern Utah. However, there were a number of MADIS Atmospheric Motion Vectors (AMVs) that indicated wind speeds as high as 161 knots, 167 knots, 170 knots, and 179 knots (below).

MODIS water vapor image + RUC winds speeds + MADIS AMVs

MODIS water vapor image + RUC winds speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs

MODIS water vapor image + RUC wind speeds + MADIS AMVs