Winds Aloft Forecast Notes
updated April 2010

The reporting stations can be viewed on an interactive map at
http://aviationweather.gov/products/nws/winds/

The forecast are published by http://aviationweather.gov/
which I think is a subdivision of http://www.noaa.gov/
This page was compiled from http://aviationweather.gov/products/nws/winds/info.php & instruction 10-812

• The forecast are a guess about what might be happening in the future.  The weather is not an exact science due a multitude of variables, so even the best guessers are somewhat wrong to varying degrees most of the time.
   
• The forecast are for a broad area so you need to do some interpolation for your local based on perceived fudge factors.  All the forecast are centered around an airport with a 3 letter identifier.  The ones for our local are Santa Barbara (SBA) and Fox Field (WJF) near Lancaster (WJF stands for Willy J Fox).
   
• It is of vital importance to determine which forecast issuance your are looking at.  If you're checking in the morning, look to see if the 6 hour forecast says For Use 1200-1800 or 1800-0000Z.  For the pre dawn issuance the 12 hour forecast covers prime time, and for the post dawn issuance, the 6 hour forecast covers prime time.
   
• (note: forecast issuance times have changed numerous times. The following is current as of 4/2/10)
  Forecast are issued 4 times a day 6 hours apart.  To create a forecast, I suspect they use balloon data as well as other information sources like pilot reports.  The balloons go up twice a day at 4 PST or 5 PDT (12Z = 4 am PST & 00Z = 4 pm PST).  The forecast times changed in August of 2005 and again sometime later.
  •  

  • Issuance	Data available	Model Run	6 hour valid times	12 hour valid times	24 hour valid times
    Pre Dawn	~ 0800 UTC ~ 0 am PST ~ 1 am PDT	0600 UTC 10 pm PST 11 pm PDT	0800-1500 UTC 0 am - 7 am PST 1 am - 8 am PDT	1500-0000 UTC 7 am - 4 pm PST 8 am - 5 pm PDT	0000-1200 UTC 4 pm - 4 am PST 5 pm - 5 am PDT
    Post Dawn	~ 1400 UTC ~ 6 am PST ~ 7 am PDT	1200 UTC 4 am PST 5 am PDT	1400-2100 UTC 6 am - 1 pm PST 7 am - 2 pm PDT	2100-0600 UTC 1 pm - 10 pm PST 2 pm - 11 pm PDT	0600-1800 UTC 10 pm - 10 am PST 11 pm - 11 am PDT
    Mid Day	~ 2000 UTC ~ noon PST ~ 1 pm PDT	1800 UTC 10 am PST 11 am PDT	2000-0300 UTC Noon - 7 pm PST 1 pm - 8 pm PDT	0300-1200 UTC 7 pm - 4 am PST 8 pm - 5 am PDT	1200-0000 UTC 4 am - 4 pm PST 5 am - 5 pm PDT
    Evening	~ 0200 UTC ~ 6 pm PST ~ 7 pm PDT	0000 UTC 4 pm PST 5 pm PDT	0200-0900 UTC 6 pm - 1 am PST 7 pm - 2 am PDT	0900-1800 UTC 1 am - 10 am PST 2 am - 11 am PDT	1800-0600 UTC 10 am - 10 pm PST 11 am - 11 pm PDT

    
    
• Each forecast issuance covers 3 forecast periods (6, 12, & 24 hours).  Which periods you look at depends on which forecast issuance is available.  Prior to August 2005 we only had a morning and evening issuance, but now we have 4 to content with.  More accurate, but more difficult to commit to memory.
  • Z time (Zulu) or UTC (Coordinated Universal Time) is international time using a 24 hour clock referenced to Greenwich England.  The earth spins toward the east, so we need to subtract from Z time to get local time:
    • Subtract 8 hours from Z time for local PST
    • Subtract 7 hours from Z time for local PDT
  • For the pre dawn issuance (0600 Data) typically displayed prior to 6 am PST
    • 06 hour forecast (12-18Z ~ 4 am to 10 am PST) for early morning conditions
    • 12 hour forecast (18-00Z ~ 10 am to 4 pm PST) for prime time conditions
    • 24 hour forecast (00-12Z ~ 4 pm to 4 am PST) is projecting late day trend
  • For the dawn issuance (1200 UTC data) typically available by 6 am PST (7 am PDT)
    • 06 hour forecast (18-00Z ~ 10 am to 4 pm PST) for prime time conditions
    • 12 hour forecast (00-06Z ~ 4 pm to 10 pm PST) to see the late afternoon trend
    • 24 hour forecast (06-18Z ~ 10 pm to 10 am PST) is projecting into early next morning
  • For the midday issuance (1800 UTC data), usually updated about noon
    • 06 hour forecast period (00-06Z ~ 4 pm to 10 pm) to see the late afternoon trend
    • 12 hour forecast period (12-18Z ~ 10 pm to 4 am) isn't of much concern to us because we don't fly in the middle of the night
    • 24 hour forecast period (18-06Z ~ 4 am to 4 pm) covers next days flying window.
  • If you look a the evening issuance, (0000 UTC data), typically updated after 6 pm PST (7 pm PDT)
    • 06 hour forecast period (06-12Z ~ 10 pm to 4 am) isn't of much concern to us because we don't fly in the middle of the night
    • 12 hour forecast period (12-18Z ~ 4 am to 10 am) is indicative of early next morning
    • 24 hour forecast period (18-06Z ~ 10 am to 10 pm) covers the next days flying window.
  • It is of vital importance to determine forecast issuance your are looking at.  If you're checking in the morning, look to see if the 6 hour forecast says For Use 1200-1800 or 1800-0000Z.  For the pre dawn issuance the 12 hour forecast covers prime time, and for the post dawn issuance, the 6 hour forecast covers prime time
• To use a forecast, locate the station you want.
  • Altitude (in 3,000 foot increments) is listed across the top, and the airports are listed vertically on the left.  After confirming the time you are looking at, find the airports on the left that you want (usually SBA and WJF).  If you're flying Ojai or Pine Mountain, your in between, so...
  • 3 data items are coded; Wind direction, Wind Speed in knots, and Temperature in degrees Centigrade
    • The first 2 digits are the direction reference to true north that the wind is coming from rounded to the nearest 10 degrees
      • 9900 / If there is no velocity, then there is no direction, so light and variable is coded as 9900
    • The 3rd and 4th digit represent velocity in knots.  Don't concern yourself too much with the difference between mph and knots because it's all a crude guess with plenty of local variation so the 15% conversion won't make much difference because...
      • If the velocity is over 100 knots, they drop the leading one from the velocity and and add 50 to the direction, so 136 knots from 320 degrees and would be represented as 8236 (first 4 digits)
    • The last 2 digits are temperature in Centigrade.  At 30,000 feet and above, it is assumed to be negative.
  • Wind and temperature are not reported near the surface, so some stations are missing lower wind and or temperature readings.
     
  • Example:  2412-03 would indicate the wind is from 240 degrees at 12 knots and the temperature is minus 3 degrees Celsius.

Winds aloft forecast are designated by either "FD or "FB"
FD is a local convention used by NOAA and ??
FB is an international convention
Our forecast are labeled as FD, but are derived from FB forecast