Appendix

Here is a short "guideline" which of the products shown in this case study that are best to be used in order to forecast convection.

When forecasting convection one should always have in mind that thunderstorms require three ingredients for their formation: moisture, lability and a lifting mechanism.

In order to evaluate the moisture content of the prevailing airmass the Dust RGB was used in this case study. As a first hint it may be helpful for the advanced forecaster, but to go into detail NWP products and observations are more useable. For forecasting the lability in the case study GII and MPEF Physical Retrieval were presented. Especially in the morning hours, when the sky is still clear, a look at both methods can help to locate possible unstable regions with the comprehension of NWP products. Also radiosoundings give a good and accurate survey over stability especially when looking at the lapse rates. Moreover the instability indices determined with the sounding data can be compared to the accordant numerical values of GII and MPEF Physical Retrieval.

Last but not least convection needs a lifting mechanism that initiates the upward motion. Therefore again NWP data is useful to locate fronts, Airmass RGBs can show whether the timing of the front is correctly forecasted. Also other synoptic scale forcing mechanisms as outflow boundaries can facilitate enough lifting to form new thunderstorms.

The lifting mechanism for air mass thunderstorm is mainly solar insolation. In order to evaluate the solar input nearly every (visible) satellite picture can be used. Also a Natural Colour RGB should be checked because it gives a hint of the soil conditions, which may be important due to differential heating.

As mentioned in the case study for forecasting the strength of convection from radiosoundings and, for a more widespread view, from NWP data should be used.

After the formation of thunderstorms the position of overshooting tops is of importance as it indicates heavy rainfall and dangerous regions for aviation. During the daytime the best method to locate overshootings is with the sandwich product of IR window BT and visible bands. Also HRVIS images alone can be very useable. After sunset one has to use IR10.8 images.

Cold ring and U/V shapes can be detected with either an enhanced IR10.8 or the sandwich product, as shown in the case study.