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The Extreme Forecast Index and Shift of Tails are presented in chart form, either for each parameter separately, or on a composite chart that caters for temperature, precipitation and maximum gusts.

Consideration regarding EFI and SOT on charts

EFI and SOT charts and diagrams refer to 24hr periods (T+00 to T+24, T+24 to T+48, T+48 to T+60 etc, etc.) and the charts run from 00UTC to 24UTC  each day.   Thus, depending on the longitude, the period of the 24hr EFI and SOT will not match local time and charts of EFI probability may span over two days in local time.  So as examples:

• in mid-western United States the period of the charts will be around late afternoon local time to late afternoon local time the next day.  
• in Australia and the Far East the period of the charts will be around mid-morning local time to mid-morning local time the next day.
• in the Near East and Eastern Africa the period of the charts will be around early morning local time to early morning local time the next day.

Severe storms may appear on two consecutive charts (e.g. afternoon local time severe storms in USA continuing through the evening local time before decaying will appear on two consecutive days but possibly with a lower probability in each period.  It is important to cater for the time differences when considering the probability of extreme weather.

EFI Web open access charts

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