Severe storms: 16th January 2008, above eastern parts of South Africa, Swaziland and Mozambique (close to Maputo)

• Martin Setvak

Below you see an example of how the storm top appearance changes depending on the color enhancement. In this case the animaton shows just a shift of the color scale from our (CHMI) “European standard scale” (200-240K) down to lower temperatures, by 20K (at 1K steps). At the same time it illustrates how one scale tuned for some region (in this case for Central Europe) needs to be modified for a different region (depending of the tropopause height and/or temperature).

The evolution of the storm indicates how the cold-U shape may result from the plume-masking mechanism (a warmer plume masking the lower cold anvil top), at least at later stage of this storm. Also interesting to see are the transverse waves that can be seen within the large system. On the outflow boundary of cirrus the appearance of gravity waves is also recgnised (towards the northern edge at the end of the animation).

Here are several last images addressing the enhancement, again for the 1800 UTC image:

01 - just a black and white linear scale, between 185 and 305 K (done using the ENVI software);

02 - the same, but with interactively modified curve of the enhancement (done using the ENVI software);

03 - black and white linear enhancement between 187 and 227 K (done using the ENVI software);

04 - color linear enhancement within the same range, 187 - 227 K, using the blue-red color table of ENVI software (which was the original “source” for the CHMI standard operational color table) … therefore in this case the colors of the color enhancement strictly correspond to those of the inserted color scale bar;

05 - this is a result of playing with the files 02 and 04 in Adobe Photoshop (CS3) … basically overlaying the image 04 by 02, and playing with the blending options. Though it is impossible to assign the colors of this image to a temperature scale, it seems to show best the thermal structure of the storm top (at least comparing it to all the other images).

06 - the same, superimposed over the 01 image (again in Photoshop).