Cyclone off the southeast coast

September 25th, 2008 |
GOES-12 sounder and GOES-12 imager water vapor channels

GOES-12 sounder and GOES-12 imager water vapor channels

A fairly large cyclone developed and intensified off the southeast coast of the US on 2425 September 2008. An animation of GOES-12 sounder and GOES-12 imager water vapor channel data (above) displayed an impressive structure associated with the system, with a well-defined dry slot wrapping around the southern and eastern quadrants of the storm. While not officially acquiring tropical (warm core) characteristics, the storm produced winds gusting as high as 55 mph and waves as high as 19 feet along parts of the Virginia and North Carolina coasts.

A sequence of AWIPS images of the 1-km resolution MODIS water vapor channel (below) showed better details of the storm structure during the period of intensification.

MODIS water vapor imagery

AWIPS images of the MODIS water vapor channel

GOES-12 visible images from 24 September and 25 September (below) revealed some impressive convection forming around the core of the storm.

GOES-12 visible images (24 September)

GOES-12 visible images (24 September)

GOES_12 visible images (25 September)

GOES-12 visible images (25 September)

GOES-11 vs GOES-13 water vapor channel images

September 23rd, 2008 |
GOES-11 and GOES-13 water vapor channel images

GOES-11 and GOES-13 water vapor images

A comparison of GOES-11 6.7µm and GOES-13 6.5µm “water vapor channel” images from 23 September 2008 (above) highlights two important changes to the GOES-13 satellite:

  1. the spatial resolution of the GOES-13 water vapor channel imagery has been improved to 4km (compared to 8km on GOES-11), which allows for more accurate detection of mesoscale “mountain waves” (or “lee waves”) that had formed over Wyoming and adjacent portions of Colorado and Montana
  2. larger batteries on board GOES-13 allow the satellite to continue to operate through Spring and Fall season “eclipse periods”, when the satellite is in the Earth’s shadow (and the solar panels cannot generate the necessary power for the instruments). The blank GOES-11 images seen in the animation above indicate outages during the GOES-11 eclipse period

The last day of Summer…

September 21st, 2008 |
AWIPS images of MODIS visible, snow/ice, and Land Suface Temperature

AWIPS images of MODIS visible, snow/ice, and Land Suface Temperature

What do you do on the last day of meteorological summer if you’re in southeastern Nunavut or far northern Manitoba in Canada? You watch fresh snow cover melt! AWIPS images of the MODIS visible channel,  snow/ice channel, and Land Surface Temperature product on 21 September 2008 (above) showed that significant snow cover was in place across that region (which had fallen a few days earlier). The many lakes in that area were still not frozen, and appeared very dark against the surrounding snow cover on the visible image. The slightly darker signal on the near-IR snow/ice image confirmed the presence of snow cover; Land Surface Temperature values were at or just below freezing at many locations (darker green colors), where presumably there was somewhat more snow cover.

The snow cover analysis from Environment Canada (below) indicated that as much as 12 cm (5 inches) of snow was on the ground in that region.

Snow cover chart

Snow cover analysis

River valley fog over Missouri and Arkansas

September 17th, 2008 |
 GOES-12 fog/stratus and low cloud base products + MODIS fog/stratus product

GOES-12 fog/stratus and low cloud base products + MODIS fog/stratus product

AWIPS images of the 4-km resolution GOES-12 fog/stratus and Low Cloud Base products and the 1-km resolution MODIS fog/stratus product (above) showed fingers of river valley fog that had formed over parts of southern Missouri and northern Arkansas at around 08 UTC (3am local time) on 17 September 2008. The soil was moist across that particular region due to heavy rainfall associated with the passage of the remnants of Hurricane Ike 3 days earlier, creating an environment favorable for the formation of radiation fog. Many of the fingers of river valley fog had formed in areas located between the METAR surface reporting stations, so there were not a lot of reports of fog across the region at that time.