It pisses me off when someone reports that the Hurricane is now a Cat 5 with 170 mph wind speed, and they NEVER tell you the altitude from which that windspeed is derived. I suspect they are making statement based on Max Sustained Windspeed (avg peek over 1 minute) at flight level (10,000 ft.) At surface level, the max sustained windspeed is going to be much, much less.
But my question is this:
If I look at current Milon windspeed at 10 m above surface, I cannot see anything higher than 68 mpg. Yet YT weather sources are reporting Milton has strengthened to CAT 5 with 170 mph winds.
Even at 10K ft., I only see 90 mph windspeed. I do see Wind Gust speed up to 110 mph, but gust are gust.
Why such huge difference between what Weather people report and what the Satellite's report?
I have done a moderate amount of reading to try and answer my own question. I have read that when storm Max Sustained is reported, the standard is suppose to be 10 m above surface. But I doubt this is adhered too.
Like I said, max sustained winds at what altitude? I don't live at 10,000 feet and could care less what it's blowing up there. It's true though that the windspeed at surface level is a percentage of what it is at 10k so that does have significance.
In Europe, to derive max sust windspeed, they look at 10 minute avg peek. The U.S. uses one minute which in my view is more like a long gust.
Here is the most detailed explanation I have found on Surface windspeed vs Flight Level windspeed.
Notice that back when they compared speed at altitude with ocean data, the estimate was much lower wind at surface. They didn't like this answer to they changed way they measured it.
"One of the more difficult problems for operational tropical cyclone forecasters is the assessment of the cyclone's maximum sustained surface wind. Even when aircraft reconnaissance data are available, these are typically obtained from the 700 mb (10,000 ft) level; from these flight-level observations, the forecaster is left to estimate the surface winds. Based on comparisons of flight-level and buoy data, Powell and Black (1990) recommended that a ratio of 63%-73% be used to reduce reconnaissance flight-level wind observations. While operational practices at the National Hurricane Center (NHC) have varied over time, in recent years surface winds have typically been taken to be 80%-90% of the flight-level wind. In view of studies such as Powell and Black, use of these relatively high ratios has periodically resulted in criticism of NHC intensity estimates."