Why did the national weather service...?

Question

Change the way they do warnings? I keep hearing that the switch from doing just counties to polygons or something? Can anyone give me information why?

Answer 1

The change was made due to the advancement of computer technology.  Some counties size are very large.  In the past...if the NWS detects a tornado over the southeast corner of a large county and is moving southeast, then puts out a warning for the county.  The who county will be alerted to this warning even though only southeast corner of that county is really in the path of  this tornado.  So you will have everybody taking cover when only that corner of the county really needed to take action.

The NWS then started warning for only a portion of the county (example southeast x*x county, norther x*x county, or Southeast and East Central x*x county.  However, many of the software for the internet and the media had was not able to break the county into sections with the borders that match what the NWS had defined on their map.  Rather than risk liability issues because the exact area did not match the actual warning, many of the private internet warning sites and media would just light up the whole county instead of sections for their graphics.

With faster and more powerful computers today, that ability is now possible where the NWS can not only make smaller size area of warnings so as to not to over warn an area, but their computers can also code up a very detailed code to map out the boundary for their users.  This would not have been possible just a few years ago when everything had to be typed out by hand.  

Today, using an advanced computer graphic tool, a forecaster can draw out a small area near and ahead of the moving severe weather cell and let the computer code out the boundary in seconds.  Both the text of the warning and the graphics would be ready in seconds for the forecaster to quickly proof-read.  Then in a few seconds, the warning of both the text and the graphic will be out for all to use.  This warning is also sent to NOAA  All-Hazards Radio for immediate broadcast by the computerized radio.  Included in this warning are SAME codes that will only alert the area where the warning is issued.  This is done again to limit the warning to only the intended areas.  

So if you are in the area of where the warning is, you are now more likely to be in the path of the severe storm and not just within the same county of where that storm may pass.

Answer 2

This is the exact same thing I have been wondering about. The National Weather Service has changes from warnings from counties to geometrical shapes (dependent upon where the storm is). This tells where exactly where the storm is, and instead of including part of the county that has no effect. So, half of a county could possible not be in effect, but the other half could. This is to tell more specifically where the storm is located.