Severe Windshear and an Approaching Haboob at Isfahan

The METAR shows a thunderstorm with rain, a 3,000 m visibility, a cumulonimbus layer at 3,000 ft, and a surface wind of 320° at 18 kt gusting 38 kt. The TAF temporarily lowers visibility to 2,500 m with thunderstorms and a lower CB layer. The pilot report of plus 15 then minus 20 kt at 500 ft is a severe windshear report, not a routine caution. A 15-kt swing in 10 seconds on a single anemometer also indicates rapid fluctuation. IRB640 is only 10 NM final at 3,000 ft, so the crew has time to go around. The balanced decision is to instruct IRB640 to go around, not to continue into a known severe windshear at 500 ft. A go-around is safer than attempting to salvage an unstable approach, especially with a haboob 8 NM away moving at 25 kt; it will reach the field in roughly 19 minutes.

IRB641 at 18 NM final should not be cleared to continue without updated information. Instruct it to hold or slow down and advise of the severe windshear report and the approaching haboob. Temporarily suspend arrivals until a pilot report or anemometer trend shows the shear has moved away. Closing the runway is justified when the shear is severe and the visibility is deteriorating, but the controller should use the correct local procedure: advise the approach unit and tower supervisor, issue the appropriate information to all traffic, and coordinate with meteorology so a SIGMET can be considered by the responsible meteorological office. The tower controller does not issue SIGMETs, but must pass the pilot report and the haboob position to the meteorological and approach units. If another runway gives a more favourable crosswind, consider it, but do not change runway merely to avoid a crosswind if the thunderstorm and shear affect all runways. The single anemometer is a limitation; pilot reports become the primary evidence.

After the go-around, give IRB640 the reason and the intended plan: 'IRB640, go around, severe windshear reported at 500 ft, climb to 5,000 ft, expect holding, contact approach.' The crew needs enough information to make its own decision about fuel and diversion. Record the pilot report verbatim, the time, the anemometer swing, the haboob position and movement, the go-around instruction, the suspension of arrivals, and the units notified. If IRB640 subsequently diverts, record the diversion and the weather given. This record is important because a severe windshear report is operational evidence; it supports the decision to suspend arrivals and protects the controller's judgement if the runway is reopened later.