Maggie’s recommendation (2015) to make equal length wind vectors at 925hPa (as a surrogate for near-surface winds):

1) In Field Selector, instead of selecting a data source, right click on Formulas 
2) click Create Formula  
3) hover your mouse over the Formula input box and right click 
4) follow Insert Procedure Call, then Grid Routines 
5) click on flowVectors(field) 
6) then in the Formula Editor multiply the flowVectors(field) by -1 (*-1) 
7) name the formula something you recognize and click Add Formula 
8) in the Formula Fields select the formula you just created and make sure the display is Vector Plan View 
9) then create the display for 3D field 
10) wind direction (Earth) @ 925hPa 
11) in the dashboard for the wind vectors you just created, change Skip: XY: to 2.0. 

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