In lookin at the info avail about the 1900 Galveston Hurricane it sure looks like the ships' captains that encountered the storm all mentioned the barometric pressure. Quite a few of them survived the storm and so researchers can use those pressure drops to approximate wind speed/ category. Out in the middle of the ocean, they'd plot position and pressure. I'd think that would be more reliable than almost anything else back then.

Heck- the weather people in DC were convinced the Galveston hurricane was on it's way across Florida when in fact Florida was just feeling the outer bands as the hurricane brushed Key West on it's way to Galveston. Ships in the GOM reported big pressure drops. Did they telegraph that info to shore? Dunno if they even had wireless telegraph in 1900...

I figure some of that mapping data had to have been exterpolated from a group of reports

'shana