Final answer:
Alternate IFR landing weather minima require that the forecasted weather at an alternate airport must have a ceiling and visibility at or above specified values. These values are commonly at least 600 feet above the lowest useable approach minima and 2 miles visibility, or higher if specified by the lowest applicable approach minima.
Step-by-step explanation:
The question is regarding the weather minima requirements for alternate airports for Instrument Flight Rules (IFR) flights. When planning an IFR flight, pilots must choose an alternate airport that they can divert to if they are unable to land at the intended destination airport due to weather or other issues. According to aviation regulations, alternate airport weather minima specify that the weather conditions at the alternate airport must be no worse than a specified ceiling and visibility. These minima ensure that there is a reasonable expectation of being able to land at the alternate airport should the need arise.
The exact numbers for the alternate minima can vary based on the type of approach available, airline or jurisdictional procedures, and can also be subject to operator specific minima. Typically, a common standard is that the forecasted weather at the alternate airport, at the estimated time of arrival, must have a ceiling of at least 600 feet above the lowest useable approach minima and visibility of at least 2 miles or the lowest applicable approach minima, whichever is higher.