Tropical Storm Jova: very cold cloud top IR temperatures

October 7th, 2011 |
GOES-15 10.7 µm IR images (click image to play animation)

GOES-15 10.7 µm IR images (click image to play animation)

GOES-15 10.7 µm IR images (above; click image to play animation) showed a large area of very cold cloud top IR brightness temperatures associated with Tropical Storm Jova over the East Pacific Ocean on 07 October 2011. Embedded within the large region of cloud top IR temperatures colder than -80º C (light purple color enhancement) were smaller areas that exhibited cloud top IR temperatures of -90º C or colder (dark purple color enhancement) — and the coldest cloud top IR brightness temperature seen was -94.65º C at 09:30 UTC. It is unusual to see cloud top IR brightness temperatures of -90º C or colder on 4-km resolution GOES IR imagery.

===== 10 October Update =====

A comparison of GOES-11 (GOES-West), GOES-15, and GOES-13 (GOES-East) visible channel images (below) showed the eye of Category 3 Hurricane Jova on 10 October 2011. Note how the difference in satellite viewing angle produces very different eyewall illumination characteristics.

GOES-11, GOES-15, and GOES-13 visible channel images

GOES-11, GOES-15, and GOES-13 visible channel images

GOES-15 is scheduled to replace GOES-11 as the operational GOES-West satellite in December 2011.

Clear Skies over the Great Lakes

October 6th, 2011 |
06 October MODIS Visible Image

06 October MODIS Visible Image

High pressure over the eastern United States on October 6th allowed a rare view of the (almost) cloud-free Great Lakes, above, from the MODIS instrument on board Terra. The clear skies also allowed observations of lake surface temperatures over the entire Lake system, shown below. (Click here for an animation between the Visible and Lake Surface Temperatures). Note that the region of turbulent, sediment-laden waters over southern Lake Michigan — (link for blog post) — are warmer than adjacent waters. The default AWIPS Lake-surface temperature enhancement shows little variations in temperature, when in fact the temperature ranges from 46 F in Lake Superior to 74 F in Lake Erie (near the mouth of Sandusky Harbor). An image with a stretched enhancement that more clearly shows the temperature variability is here. Lakes Michigan, Huron and Ontario continue to show the effects of persistent easterly winds associated with a series of cut-off lows that have passed south of the Great Lakes in the past weeks: cold near-shore temperatures associated with upwelling in the eastern part of the basins.

06 October MODIS Sea Surface Temperature Image

06 October MODIS Sea Surface Temperature Image

Screenshot of AWIPS including MODIS True-color image, 06 October

Screenshot of AWIPS including MODIS True-color image, 06 October

MODIS multi-channel data can be combined to produce a true-color image in the AWIPS environment. In this case, above, the sediment-laden lake waters over southern Lake Michigan jump out. Fall colors over northern Wisconsin and the southern Upper Peninsula of Michigan are also evident. More true-color imagery is available at the MODIS today site: Link.

Okreek Fire in south-central South Dakota

October 5th, 2011 |
GOES-11 + GOES-15 + GOES-13 visible channel images

GOES-11 + GOES-15 + GOES-13 visible channel images

Strong southerly winds (gusting as high as 50 mph) helped a large grassland fire (named the Okreek fire) spread rapidly northward across south-central South Dakota during the afternoon hours on 05 October 2011. The light gray smoke plume and the dark burn scar grew very quickly, which could be seen on GOES-11 (GOES-West),  GOES-15, and GOES-13 (GOES-East) visible channel images (above). Each of the 3 sets of images is displayed in the native projection of the respective satellite.

The corresponding 3.9 µm shortwave IR images from each satellite (below) showed the large and intense “hot spot” (dark black to yellow pixels) associated with the Okreek fire. Note there were also a few other smaller fires burning in other parts of central South Dakota during that time period, which also exhibited very intense hot spot signatures.

GOES-11 + GOES-15 + GOES-13 shortwave IR images

GOES-11 + GOES-15 + GOES-13 shortwave IR images

A comparison of 250-meter resolution false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site from before (04 October), during (05 October), and after (07 October) the Okreek fire revealed the development and growth of the 26 mile long burn scar (which appears as the light brown line). The bright pink feature on the 05 October image was the heat signature of the active front line of the fire, which was rapidly advancing northward on that day.

MODIS false-color RGB images from 04 October, 05 October, and 07 October 2011

MODIS false-color RGB images from 04 October, 05 October, and 07 October 2011

 

Fog and stratus in the Ohio River Valley and central Appalachians

October 5th, 2011 |
MODIS and GOES-13 fog/stratus product images

MODIS and GOES-13 fog/stratus product images

Strong nocturnal radiational cooling beneath a large area of high pressure centered over the Ohio River Valley led to the formation of widespread areas of fog and stratus on 05 October 2011. AWIPS image comparisons of the 1-km resolution MODIS and the 4-km resolution GOES-13 fog/stratus products at 03:30 UTC or 11:30 pm local time (above) and 07:45 UTC  or 3:45 am local time (below) demonstrated the clear advantage of having improved spatial resolution to detect the more subtle features such as river valley fog.

MODIS and GOES-13 fog/stratus product images

MODIS and GOES-13 fog/stratus product images

 

To compliment the improved fog/stratus detection capabilities offered by higher spatial resolution, other products are being developed (as part of the CIMSS participation in GOES-R Proving Ground activities) that provide more quantitative information about areas of fog and/or low cloud: for example, Fog Depth, Marginal Visual Flight Rules (MVFR) Probability, and Instrument Flight Rules (IFR) Probability (below). In this case, the 07:45 UTC products indicated that the Fog Depth values were as high as 1231 feet (cyan color enhancement) over parts of northern West Virginia, where there were also MVFR Probabilities greater than 90% and IFR Probabilities greater than 75% (brighter red color enhancement).

GOES-13 fog/stratus product, Fog Depth, MVFR Probability, and IFR Probability

GOES-13 fog/stratus product, Fog Depth, MVFR Probability, and IFR Probability