Tool 7:  Case Study – Thunderstorm Case in West Africa


Note:  This case study is provided in French by L’ Agence  pour la  Sécurité de  la  Navigation  Aérienne  en  Afrique  et  à  Madagascar (ASECNA) as an example of using a case study to evaluate certain performance criteria.  The following condensed description has been translated into English.  The case study is extracted from a direct observation assessment process during the wet season.  It is an example of best practice with the hope that it may be emulated in other locations for important but infrequent events.  In tropical regions, thunderstorms tend to be more seasonal and are very rare in the dry season.   Demonstrating this competence would not be practical in dry season using direct observation.  Successful completion of the case study would satisfy several performance criteria.  As with many competencies, there is no guarantee that success on the test or case study would transfer to a real-time situation.  Should deficiencies be noted later, corrective action would be required and should be described within the quality management system of the specific organization.  Human nature is such that, even for perfectly demonstrated competence, in a real situation, there is no absolute certainty that the individual will demonstrate the same competence on a different day.  There is a strong probability of continued competence but no guarantee.  For this reason, as part of a quality management system, ongoing competency demonstration is required.  


Satisfies the following performance criteria:

1.3 assessing the need for amendments

2.1h forecasting thunderstorms

2.3a monitoring adjacent regions

2.3b liaise with adjacent regions

3.1a forecasting severe thunderstorms

5.2 delivering briefings

The full case study in French, with accompanying information, can be downloaded from (insert link here).


The forecaster is asked to prepare a briefing for a flight crew departing at 13h50 UTC with the flight route LoméCotonouNdjamenaDouala.  The forecaster is expected to prepare

·         forecast winds and temperatures for FL180, FL340 and FL450

·         high altitude significant weather chart valid August 4 at 18 UTC

·         ascent forecast from Lomé (Togo, DXXX)

·         approach forecast for Douala (Cameroon, FKKD)

In addition, he or she is asked to consider the forecasts provided and what, if any action should be taken.  This could include amending forecasts, issuing warnings, contacting clients or other regions. 


As part of the case study, the forecaster is given access to

·         standard analysis and forecast charts for August 4

·         forecast upper level winds for 18 UTC August 4 for FL180, FL340, FL390, FL450

·         WAFC sig weather chart FL250 and higher valid 18 UTC August 4

·         satellite imagery

·         surface and aircraft reports from the region

·         any TAFs or SIGMETs in effect in the region

·         NWP


Assessment criteria – case study outcomes

·         The forecaster should consider the enroute portion of the flight from Lomé to Cotonou (Benin, DBBB) to Ndjamena (Chad, FTTJ) and finally to Douala. 

·         The forecaster should notice the convective development over northwestern Nigeria, near the border with Niger.  This more intense convection extends over northern Togo and Benin. 

·         The motion of this convective complex should be noted (toward the SW at 15-20 m/sec).

·         In addition, the forecaster should remark that the thunderstorms may reach Niamgtougou (Togo, DXNG) within the next three hours.  A TAF amendment should be considered if required. 

·         The forecaster should examine forecasts from adjacent regions and initiate communication as appropriate.

·         The examination of the satellite image at 11 UTC suggests that the convective area might be weakening.  However, examination of analysis and model data shows confluence at 700 hpa as well as a convergence zone at 850 hpa over the northern and north-eastern part of Togo. In addition, there is a good moisture supply.

·         Thus, the forecaster should expect the area of thunderstorms to continue its current motion while intensifying. 

·         The forecaster should consider the requirement for a SIGMET as well as any associated warnings. 


A similar case study model could also be developed for other infrequent or seasonal phenomena such as

·         2.1e - Forecasting precipitation

·         2.1f - Forecasting reduced visibility, onset and duration

·         2.1g - Forecasting obstructions to vision

·         2.1h - Forecasting thunderstorms

·         2.1i - Forecasting turbulence

·         2.1j - Forecasting icing

·         2.1k - Forecasting wake vortex formation, movement and dissipation

·         3.1a - Warnings for severe thunderstorms

·         3.1b - Warnings of severe turbulence

·         3.1c - Warnings for severe winds, wind shear, variability and gusts

·         3.1d - Warnings for severe icing

·         3.1e - Forecasting hazardous phenomena affecting aerodromes