Convective outlooks

[Adam Childers]

Why do they use arrows to show the regions on these severe weather discussions?

 

[Rob Wadsworth]

Since I am a newbie too, I'll venture a guess.
If you are referring to the Western Continental US (Western 'Conus'), I noticed that it is following a clockwise pattern.
A clockwise pattern would have to be a dominant High pressure system/flow.
As a Low Pressure system would have a counter-clockwise flow and rotation.

 

[Lou Ruh]

Why do they use arrows to show the regions on these severe weather discussions?

This is done because the outlook product includes a description that says "THERE IS A <SLGT/MDT/HIGH> RISK OF SVR TSTMS TO THE RIGHT OF A LINE ..." or "... TSTMS ARE FCST TO THE RIGHT OF A LINE FROM ..." . You can see this text if you click on the link in the outlook that says something like "CLICK TO GET WUUS01 PTSDY1 PRODUCT". Without the arrow, there'd be no way to know the right side from the left side of the line that is drawn.

 

[Bobby Prentice]

Why do they use arrows to show the regions on these severe weather discussions?

This is done because the convective outlook graphics are based on the text version of the product which describes risk areas as: "THERE IS A RISK OF SVR TSTMS TO THE RIGHT OF A LINE ..." or "... TSTMS ARE FCST TO THE RIGHT OF A LINE FROM ..." .

Personally, I wish SPC would also lightly shade-in the risk areas on their graphics to make them easier to read.

Don't forget, the convective outlook probability graphics provide a superior forecast for specific severe weather hazards (tornado, wind, hail, any severe) and should be the primary product anyway. The old Slight, Moderate and High Risk outlook categories are dinosaurs that should be retired to the dust bin of history.