[USAF0021]

The pressure at the surface is extrapolated (EXTRAP) from the 700 mb level in order to get an estimate. (The hurricane hunters can't actually fly near the surface, they fly above where the winds are less violent (This is true for warm core cyclones, winds decrease with height, which is the opposite for cold core cyclones (the typical L's that you see at the midlatitudes on a weather map)) It says the height where 700 mb is found is at 2604 meters, so they use an equation that estimates what the pressure would be if you brought a parcel of air at the 700 mb level down due to the surface.

[snowsislander]

The pressure at the surface is extrapolated (EXTRAP) from the 700 mb level in order to get an estimate. (The hurricane hunters can't actually fly near the surface, they fly above where the winds are less violent (This is true for warm core cyclones, winds decrease with height, which is the opposite for cold core cyclones (the typical L's that you see at the midlatitudes on a weather map)) It says the height where 700 mb is found is at 2604 meters, so they use an equation that estimates what the pressure would be if you brought a parcel of air at the 700 mb level down due to the surface.

Thanks, that makes perfect sense.