MODIS true color images (30 September, 01 November, 10 November)

A sequence of three MODIS true color images from the SSEC MODIS Today site (above) showed an increasing level of turbidity of the water along the Gulf Coast — the 3 images are from 30 September, 01 November, and 10 November 2009. This increase in turbidity can be directly attributed to the runoff of sediment-rich water due to heavy precipitation across much of the Gulf Coast states from late October into early November, as shown in the 14-day observed precipitation map (below). Special thanks to Steve Davis and Jeff Craven at the National Weather Service forecast office at Milwaukee/Sullivan for creating/capturing these images and bringing this case to our attention!

14-day observed precipitation

AWIPS images of the MODIS Sea Surface Temperature (SST) product (below) showed that the Gulf of Mexico immediately offshore was significantly colder due to this discharge of sediment-rich water from rivers draining from the Gulf Coast states — SST values were in the low to mid 60s F (darker green colors) right along the coast, compared to the mid 70s to near 80º F (darker red colors) farther offshore.

MODIS Sea Surface Temperature product (November 10 - 12)

MODIS true color and false color images

A comparison of MODIS “true color” and “false color” Red/Green/Blue (RGB) images (above) showed that significant amounts of ice remained in parts of southern Hudson Bay and northern James Bay in Canada on 10 August 2009. On the true color RGB image (using MODIS bands 01/04/03), the ice did not appear as as bright as the surrounding clouds, and had a slightly “light blue” appearance. On the  false color RGB image (using MODIS bands 02/07/07), the ice (along with clouds that were composed of ice crystals) exhibited a darker red appearance, in contrast to the cyan to white colored supercooled water droplet clouds.

Also note the hazy appearance over parts of Ontario, just to the west of James Bay: this was due to smoke aloft from recent fire activity in Alaska and the Yukon Territory.

A map of the departure from normal ice concentration (below, courtesy of the Canadian Ice Service) indicated that there were large areas where the ice  was in the 7/10ths to 10/10ths range above the normal concentration for the date (darker blue colors). The persistence of a deep area of low pressure just south of Hudson Bay (July 2009 mean 850 hPa geopotential height) kept that region (along with much of the eastern US) unusually cold during the summer, which undoubtedly slowed the rate of ice melt in Hudson Bay and James Bay.

Ice Concentration (departure from normal)