I agree...picking the gradient is more difficult especially in shore where the isobars direction are more variable...offshore they are more circular. So, some propose that you can know by looking at the isobars! I think as
an approximation of a dynamic system, you may not get it right (perfect) every time but given the vector of the
weather system and your position you should understand your situation with a good feel for the magnitude.
I’ve toyed with some geometric approximations but they are not passing the simple, quick and dirty quotient. I think its possible to do some higher math but, that higher math effort runs the risk of alienating some.
Following up on Ricks question...the offset from true geostrophic wind is explained below with a discussion of Ekmann Spiral. Which applies to ocean currents as well as atmospheric ones.
To let the cat out of the bag, I think drawing a rectangle between isobars with some limits on the included angles to fault the process when the geometry is ambiguous. The midpoint would be the target point with a mean value derived from the two side directions + 30° Ekmanm (friction ) offset.
If it intrigues you? Fine! If you find yourself put off by codifying your seat of the pants judgement, or more comfortable with GRIB strategies where the interpolation is taken care of for you. That’s cool too!
I think the modern PC is capable of the analytics, FitzRoy was onto something when he started trending barometric pressure. I felt it was worthy of more thought last
winter when I told my friends by
cell phone...”you better be somewhere safe before the barometer on the bulkhead reaches xxxxx millibar. Trend it, we will have an idea how much time you have?
Finally, I apologize for thinking out loud, its a product of the digital forum method of collaborating....
PS In the open ocean with, relative to land, smooth surface roughness, it’s effect is less but probably handled just fine with GRIBS fore true
blue water mariners.
Ekman spiral - AMS Glossary
Linear Mode
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