Since Rockoon posted up my animated gif, let me jump in here and try to explain a couple things. I've got the Hurdat data and did some research with it a couple months ago and can group the storm plots by distance from land.
Rockoon is right to make the point about there being a difference between detected and not detected. The ones closest to land are more likely to have been counted fairly accurately early on in the record. A human had to be there to make the record.
Here's a count of plots of hurricane force winds from 0-300 miles and 301-1200 miles from land for 1851-1900 and 1951-2000.
Code:
Landfall-> 0-300 miles 301-1200 miles
1851-1900 3342 plots 1165 plots
1951-2000 2933 plots 1921 plots
As can be seen the 1851-1900 period had a small edge on observations within 300 miles of land, while 1951-2000 had a huge edge from 301-1200 miles from land. The most likely reason for the difference is satellites have improved detection. A ship actually had to run into a storm in the 1800's in order to record the observation if it was far from land. Not only that, but the ship had to survive and turn in it's log for it to be recorded. You won't find any Category 5 winds in the 1800's, because no ship captain is going to intentionally continue to head into a storm just to find it's highest wind speed.
A couple more things. The average wind speed at the time of storm discovery in the 1800's was around 50kts. For 1951-2000 that speed was around 30kts. 86 storms during the 1800's weren't even discovered until they were already hurricane speed, and a couple of those were in excess of 100kts at the time. All storms during the 1951-2000 period were discovered prior to reaching hurricane strength.
I see no other reason for observations to be roughly equal within 300 miles of land yet have a big difference farther out, other than detection ability. Any comparison of a simple count of observations by satellite with pre-satellite era is meaningless. It's simply a count of what was observed, not what happened.
The warm water areas of the Gulf Mexico, Caribbean, and the Gulf Stream along the east coast fall within the 300 miles range. So, water temperature can't be the cause of the difference in observation count.
Shane isn't right either, due to exaggerating by saying mildest ever, and not simply saying mild. Mildest assumes knowledge of the full history. We only have records since 1851 and those aren't even comprehensive.
I think 1851-1900 was as bad and probably worse than 1951-2000 given the disparity in observational quality between the two periods. Unfortunately there isn't any way to resolve the observational discrepancy accurately.
Just so you get an idea of what 300 miles from land looks like, here's a gif of the area that covers plots within 300 miles of land for the 1851-1900 period. The later period would look basically the same with a few hundred less plots drawn. No category 5 plots during the 1800's. Those are found almost exclusively over water, and any ships that might have encountered such winds probably didn't survive to return with records. No plots of less than hurricane force are included.
Blue = category 1,2. Red = category 3,4.
Click to enlarge.
edit... Faulty memory. Changed 100 to 86 after checking my records.
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