Space shuttle launch commit criteria are the criteria which must be met in order for the countdown and launch of a space shuttle mission to continue. These criteria relate to safety issues and the general success of the launch, as opposed to supplemental data.[1]
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The weather conditions[2] NASA requires during countdown and launch are specified for "prior to loading external tank propellant" and "after loading propellant has begun". Weather forecasts are provided by the 45th Weather Squadron at nearby Patrick Air Force Base with concerns such as thunderstorms, winds, low cloud ceilings, or anvil clouds noted in the report.
Tanking will not begin if the 24 hour average temperature has been below 41 °F (5 °C), the wind is observed or forecast to exceed 42 knots (78 km/h; 48 mph) for the next three hour period, or there is forecast to be greater than a 20% chance of lightning within five nautical miles of the launch pad during the first hour of tanking.
After tanking begins, the countdown shall not be continued nor the Shuttle launched if any of the weather criteria are exceeded.
Once propellant loading has begun, the countdown will be stopped if the temperature remains above 99 °F (37 °C) for more than 30 consecutive minutes. The minimum temperature the countdown may proceed at is determined by a table of temperatures determined by wind speed and relative humidity ranging from 36 °F (2 °C) (high humidity, high winds) to 48 °F (9 °C) (low humidity, low winds). In no case may the space shuttle be launched if the temperature is 35 °F (2 °C) degrees or colder.
For launch the wind constraints at the launch pad will vary slightly for each mission. The peak wind speed allowable is 34 knots (63 km/h; 39 mph). However, when the wind direction is between 100 degrees and 260 degrees, the peak speed varies and may be as low as 20 knots (37 km/h; 23 mph).
None at the launch pad or within the flight path