How long are winds aloft good for

Skyfox on Nov 15, I love obscure questions like this! Maybe we can figure it out by going through some sample info. Explanation of Figure The heading indicates that this FD was transmitted on the 15th of the month at Z and is based on the Z radiosonde. The valid time is Z on the same day and should be used for the period between Z and Z.

The heading also indicates that the temperatures above 24, feet MSL are negative. Since the temperatures above 24, feet are negative, the minus sign is omitted. Forecasts are built from models based on those observations and issued four times a day at Z, Z, Z, and Z with forecasts for 6 hours out, 12 hours out, and 24 hours out. So please take a look at AC G, page , table It seems like the for-use time can vary. As it says in the above example, that particular FD forecast was issued at Z based on data from Z.

However, this does bring up the question: if it starts being valid at Z, what if you want to take a flight at Z? Or do you use the previous forecast from Z assuming it overlaps past Z? I told it to plan on a 23 hour 59 minute flight so it would need the 6 hour, 12 hour, and 24 hour forecasts. The second, hour forecast becomes valid at Z 12 hours after the observation and is good for a 9 hour span until Z. And the third, hour forecast becomes valid at Z the next day, 24 hours after the observation, and is good for a 12 hour span until Z.

PDF] This means that we can use a forecast for a flight that begins during the for-use time but before the valid time of that forecast.

In practice, I would use the earliest forecast that comes up in the briefing and overlaps my flight. It appears they have standard valid times every 6 hours, and then forecast for a block of time around that valid time. While these are standard times, you should consult the specific information available in the product header that has this information. For example:. This says the product is valid at 06Z and for use from 05Z to 09Z and the data is based upon the 00Z forecast model run. The valid time of the forecast is the first day of the month at UTC.

The forecast winds and temperature are to be used between and UTC. Every forecast has a valid time, and in fact valid times are different for the same type of forecast in different locales , for example TAFs are valid for either 4 or 6 hours.

My answer, therefore, is that the valid time for ANY forecast is whatever the forecast itself says. So a Z chart would be valid Z - Z. In raw form they usually have a product code associated with them. Example: PWBE Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How long is a winds and temperatures aloft forecast valid for?

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