Confusion: 12 Hr SFC Prog vs. 24 Hr SFC Prog

[leptserkhan]

Hello and good morning,

I'm trying to discern the difference between the 12 and 24 hour SFC Prog. charts at this link:

http://aviationweather.gov/products/swl/

You will see in the chart two rows at the bottom one row labeled 12 Hr SFC and the row directly beneath it labeled 24 Hr SFC, yet both have a column identified as, for example, issued at 12 zulu.

What is the difference between these charts and if they are both valid at the same time and issued at the same time, why the difference in graphics?

Thank you.

 

[chucky]

Well, 12 hours after a given 24 hour forecast is issued, there will be a 12 hour forecast issued for the same valid time. Since forecasts can change over time, that is why the two charts might look different. Is that the source of your confusion?

 

[leptserkhan]

Hmmm... not really. I guess it would be helpful for my understanding if I knew the sequence in which I'm supposed to read them to get the most complete weather picture. Do I read along the 12 hr left to right, then drop down and read the 24 hr left to right?

 

[chucky]

Best, I think, to read the most recent 12hr, then the most recent 24hr. I'm not sure what value there is in reading the older prog charts, unless you're interested to see how well the forecasts did with the current conditions, or how quickly the forecasts have been changing.

 

[leptserkhan]

Okay, I think I got it now. I'm supposed to read the top-most column heading where it says "last updated", is that right? That will tell me which of the charts are the most recent. Is that right?

 

[leptserkhan]

Okay thanks for your help all.

I understand it now.

PROP!!