[calcapt]

Originally Posted by FlyChicaga

Approximately 10 minutes away from your intended destination (a regional midwest airport), you are informed by the approach controllers that a storm is just hitting the field, and all arrivals have been halted. They offer to provide you delay vectors while the storm passes, which should happen in the next 20 minutes. It is a very large, fast-moving cell. You pull up the D-ATIS on your ACARS, and it says:

KABC ATIS INFO K 1205Z SPECIAL. 25030G65 1/2SM +TSRA BKN003 OVC013CB 17/10 A29.85 (TWO NINE EIGHT FIVE). ILS APPROACH RUNWAY 18L AND RIGHT IN USE. DEP RUNWAYS 18L AND RIGHT. ADVISE CONTROLLER ON INITIAL CONTACT YOU HAVE INFO K.

You are arriving to this airport from the West. Your alternate is behind you; you flew over your alternate on the way into your destination. The METAR for your alternate is as follows:
KXYZ 081152Z 32023G28KT 10SM BKN023 BKN029CB 19/11 A2991 RMK AO2 PK WND 31033/1124 SLP195 T01870106 10067 20039 51036

Calculating your holding fuel, you can fly around for about 10 minutes before you'll be burning into your reserve fuel. What this means is, you currently have enough fuel to hold for 10 minutes, fly to your destination, go missed, fly to your alternate, and have 45 minutes of reserve fuel thereafter.

Question is, do you hang around for another 10 minutes passed your calculated "decision time," knowing it is likely you'll be able to get into your intended destination airport? You are on the backside of the storm in decent weather conditions, which are the conditions expected in about 20 to 25 minutes. Or, do you divert to your alternate airport since you would be burning into your calculated reserve fuel waiting for the storm to pass?

Captain, you now have only five minutes left to make a decision before you reach your calculated "decision fuel." The alternate you have is the closest suitable alternate available.

Easy. Hold for 10 minutes and then get a destination Wx update. If the weather is still over the field and not moving much, go to your alternate as you really don't have a choice. If the Wx is moving as predicted and will clear shortly, I would wait a few more minutes until it does clear. I would then call dispatch after it had cleared and asked him/her to delete my alternate requirement since Wx is no longer an issue. I now have extra fuel to land at my destination safely.