screaming_emu
11-11-2005, 06:44 AM
In one of the other threads, it was requested that somebody make a post in here about how to read a TAF. So as requested, here it is. If you have any other questions, or if something doesn't make sense, just post and I'll try to explain it a little better.
First off, I've found that the best aviation weather source is http://adds.aviationweather.gov That is where I reccomend you go if you are looking for a TAF. Just click on the TAF tab at the top and type in the airport code (works for airports all over the world if I remember correctly). Hit submit and you'll be all set.
The best way to learn something in my opinion is through application. So what instead of just saying what each section and abreviation stands for, I'm going to post a real one from a place that is having interesting weather, and then we'll dissect
First off, A TAF is a product put out by the national weather service to describe the expected weather conditions over a 24 hour period. The only downside is that it only covers a 5 mile radius around the airport. that's not exactly a big area, but unless you're having some strange weather, it should work pretty well for the surrounding area too, just not always. Another thing to point out is that not every airport has a TAF, its only selected airports, usually the larger/more frequently used ones in a given area. TAFS are issued 4 times a day at 0000 0600 1200 and 1800 Zulu (GMT).
I have no idea where STS is, other than that its in California, but this is the TAF we're gonna look at.
KSTS 110541Z 110606 VRB03KT P6SM SKC
FM1200 00000KT 1/4SM FG VV001
FM1700 VRB03KT 5SM BR SCT006
FM1800 16007KT P6SM SKC
FM0500 VRB03KT P6SM SKC
Top Line-Gives you some general info about the TAF
KSTS-Airport Identifier
110541Z-Date and Time the forecast was issued. In this case it was issued on the 11th day of the month at 0541Z. All times in a TAF are Zulu (GMT)
110606- This is the time which the forecast is valid. Again, the first number is the day of the month (the 11th) from 06Z until 06Z the following day. They leave out the date because its understood that with the forecast being valid for 24 hours, its probably going to expire on a different day than it was issued.
VRB03KT P6SM SKC -The last part of the top line is the expected conditions for the forecast.
Body-Obviously, in 24 hours the weather can change quite a bit from what is first forecast. The body of the TAF lists what the expected changes in weather are, as well as the estimated times that the change will occur.
FM1200 00000KT 1/4SM FG VV001-So from 6Z on, you can expect the weather to be what it says in the upper line. But looking at the first line of the body, it says From 1200Z (FM1200) the wind will be calm. (00000KT ). Usually the first 3 numbers is the direction the wind is coming from, and the following two, the speed. But when the wind is calm, 00 is the default direction. Visibility will be 1/4th of a Statute mile (1/4SM ) in fog (FG). Vertical Visiblity, or how far you can see if you looked straight up, is 100ft (VV001). The number following VV is in hundreds of feet, so 010 would be 1,000 feet. You will only see VV included in the TAF when visibility is restricted by something such as fog.
The rest of the TAF is set up just like the first line. There are a couple things things you may see different in other TAFs. It would take forever to cover them all in depth, so I'll try to give a quick overview of what they might be and feel free to ask if you have any specific questions about something I didn't cover.
One of these things is different weather phenomenon (which I'll list a bunch of commonly used ones at the bottom of the post). In this TAF you see fog. Other things that might be in there are rain, snow, sleet, hail, mist, etc. There may be qualifiers in front of these. Such as +RA means heavy rain -RA means light rain, and if its just RA it is moderate.
If you're wondering what P6SM means, its +6 miles. 6 miles is the most you'll see forecasted in a TAF. Visibility could be well more than 6 miles, but they feel that if it gets to 6, its good enough.
Another thing you may see different is that instead of FM1200 at the beginning of a line, you'll see TEMPO 1214. That means whatever they are forecasting in that line is going to be temporary from 12z to 14z. After 14Z weather is expected to go back to whatever it was before the change.
TAFs are fairly uniform throughout the world with a few minor differences. One of the more obvious ones is that visibility will be reported in meters. The max forecasted visibility then is usualy 9999 meters. US military bases also report their visibility in meters because their pilots are flying all over the world, so they feel its a help to keep their pilots from needing to do conversions.
Some other countries will report winds in meters per second, though I believe most of them use Knots.
That's about all I can think of for right now. I know its a lot of stuff at once, and it wasn't exactly organized the best, but definately let me know if you need me (or anyone else) to clarify anything, or if you find something I didn't cover.
Here's a list of commonly used abreviations found in TAFs for weather phenomenon, (some of them make sense, some of them dont even come close):
Precipitation
DZ-Drizzle RA-Rain SN-Snow SG-Snow Grains IC-Ice pellets
PL-Ice Pellets GR-Hail GS-Small Hail or Snow Pellets UP-Unknown Precip
Obscuration
BR-Mist FG-Fog DU-Dust HZ-Haze PY-Spray VA-Volcanic Ash FU-Smoke
Other
PO-Dust/Sand whirls SQ-Squalls FC-Funnel Cloud +FC Tornado/Waterspoout
SS-Sandstorm DS-Dust Storm
First off, I've found that the best aviation weather source is http://adds.aviationweather.gov That is where I reccomend you go if you are looking for a TAF. Just click on the TAF tab at the top and type in the airport code (works for airports all over the world if I remember correctly). Hit submit and you'll be all set.
The best way to learn something in my opinion is through application. So what instead of just saying what each section and abreviation stands for, I'm going to post a real one from a place that is having interesting weather, and then we'll dissect
First off, A TAF is a product put out by the national weather service to describe the expected weather conditions over a 24 hour period. The only downside is that it only covers a 5 mile radius around the airport. that's not exactly a big area, but unless you're having some strange weather, it should work pretty well for the surrounding area too, just not always. Another thing to point out is that not every airport has a TAF, its only selected airports, usually the larger/more frequently used ones in a given area. TAFS are issued 4 times a day at 0000 0600 1200 and 1800 Zulu (GMT).
I have no idea where STS is, other than that its in California, but this is the TAF we're gonna look at.
KSTS 110541Z 110606 VRB03KT P6SM SKC
FM1200 00000KT 1/4SM FG VV001
FM1700 VRB03KT 5SM BR SCT006
FM1800 16007KT P6SM SKC
FM0500 VRB03KT P6SM SKC
Top Line-Gives you some general info about the TAF
KSTS-Airport Identifier
110541Z-Date and Time the forecast was issued. In this case it was issued on the 11th day of the month at 0541Z. All times in a TAF are Zulu (GMT)
110606- This is the time which the forecast is valid. Again, the first number is the day of the month (the 11th) from 06Z until 06Z the following day. They leave out the date because its understood that with the forecast being valid for 24 hours, its probably going to expire on a different day than it was issued.
VRB03KT P6SM SKC -The last part of the top line is the expected conditions for the forecast.
Body-Obviously, in 24 hours the weather can change quite a bit from what is first forecast. The body of the TAF lists what the expected changes in weather are, as well as the estimated times that the change will occur.
FM1200 00000KT 1/4SM FG VV001-So from 6Z on, you can expect the weather to be what it says in the upper line. But looking at the first line of the body, it says From 1200Z (FM1200) the wind will be calm. (00000KT ). Usually the first 3 numbers is the direction the wind is coming from, and the following two, the speed. But when the wind is calm, 00 is the default direction. Visibility will be 1/4th of a Statute mile (1/4SM ) in fog (FG). Vertical Visiblity, or how far you can see if you looked straight up, is 100ft (VV001). The number following VV is in hundreds of feet, so 010 would be 1,000 feet. You will only see VV included in the TAF when visibility is restricted by something such as fog.
The rest of the TAF is set up just like the first line. There are a couple things things you may see different in other TAFs. It would take forever to cover them all in depth, so I'll try to give a quick overview of what they might be and feel free to ask if you have any specific questions about something I didn't cover.
One of these things is different weather phenomenon (which I'll list a bunch of commonly used ones at the bottom of the post). In this TAF you see fog. Other things that might be in there are rain, snow, sleet, hail, mist, etc. There may be qualifiers in front of these. Such as +RA means heavy rain -RA means light rain, and if its just RA it is moderate.
If you're wondering what P6SM means, its +6 miles. 6 miles is the most you'll see forecasted in a TAF. Visibility could be well more than 6 miles, but they feel that if it gets to 6, its good enough.
Another thing you may see different is that instead of FM1200 at the beginning of a line, you'll see TEMPO 1214. That means whatever they are forecasting in that line is going to be temporary from 12z to 14z. After 14Z weather is expected to go back to whatever it was before the change.
TAFs are fairly uniform throughout the world with a few minor differences. One of the more obvious ones is that visibility will be reported in meters. The max forecasted visibility then is usualy 9999 meters. US military bases also report their visibility in meters because their pilots are flying all over the world, so they feel its a help to keep their pilots from needing to do conversions.
Some other countries will report winds in meters per second, though I believe most of them use Knots.
That's about all I can think of for right now. I know its a lot of stuff at once, and it wasn't exactly organized the best, but definately let me know if you need me (or anyone else) to clarify anything, or if you find something I didn't cover.
Here's a list of commonly used abreviations found in TAFs for weather phenomenon, (some of them make sense, some of them dont even come close):
Precipitation
DZ-Drizzle RA-Rain SN-Snow SG-Snow Grains IC-Ice pellets
PL-Ice Pellets GR-Hail GS-Small Hail or Snow Pellets UP-Unknown Precip
Obscuration
BR-Mist FG-Fog DU-Dust HZ-Haze PY-Spray VA-Volcanic Ash FU-Smoke
Other
PO-Dust/Sand whirls SQ-Squalls FC-Funnel Cloud +FC Tornado/Waterspoout
SS-Sandstorm DS-Dust Storm