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Hurricanes are rated on estimated surface winds, not flight level. "Surface" is generally considered about 30 to 35ft off the ground. "Surface" winds of hurricanes can be estimated by calculating flight level wind speed down to a lower value for 'ground level' (doesn't mean those values are actually translated to the ground level (ie: you need storms to help pull those winds downward, etc.)), wing affixed SFMR (Step frequency microwave radiometer), dropsondes which continuously send data back to plane from airplane deployment to water surface, possibly some data with Coyote UAS drone (don't know if they launched this time or not), satellite estimates (Dvorak technique, infrared cloud temperatures, eye clarity/shape, etc.), ground and aircraft weather radar. etc.
Now that wind speed just has to be in one tiny spot to get the rating (part of why other rating systems may come fwd at some point to reflect more impact rating scale for diff areas one day perhaps).
I don't know what it came ashore as, but several hours before it was definitely a strong major hurricane. But just as neared shore, radar showed system appeared to be undergoing eyewall replacement and satellite presentation degraded as well.
You'll notice this is probably the first storm I didn't post any surface winds obs on. Very very few data observation points that region of FL and storm was structurally changing as came ashore. Was not easy to decipher what was actually happening near ground for me. Plane data also indicates max winds may have only been in about 10mile radius. Extremely small.
Hurricane rating during storm advisories is like football...ruling on the field stands until replay overturns call. NHC will look at all the data for their final report as it all doesn't come in at real time and fully. It'll look at more data that wasn't available in real time, and of the data that was they can re-review and ground observation readings and damage indicators.
Sun evening - Idalia remnants slowing down just South of Nova Scotia. Models seem to thing it'll stay there a couple days before moving on. May get close enough for some showers / breezy conditions there and Newfoundland perhaps.
Thankfully she landed in a sparsely populated area. Unfortunately the area has never been hit by a major either so infrastructure wasn't prepared for this.
Hurricanes are rated on estimated surface winds, not flight level.
Incorrect. Unless you're talking about another kind of "rating". The category given for a hurricane is based on flight level where the max wind was found.
Incorrect. Unless you're talking about another kind of "rating". The category given for a hurricane is based on flight level where the max wind was found.
WeatherNation didn't provide the relevant additional context for their statement, as the rating is based on surface wind speed with NHC.
Per NHC guidlines 2021 May update report(about 1/3 to 1/2 thru the first paragraph) states "The maximum sustained surface wind speed (peak 1-minute wind at the standard meteorological observation height of 10 m [33 ft] over unobstructed exposure) associated with the cyclone is the determining factor in the scale." (Found on this page, under the categories listed and video the first link under More Information PDF link https://www.nhc.noaa.gov/aboutsshws.php )
Looking back at the 5pEDT 29Aug advisory air recon data had flight level winds of 91knt(104.7mph), and surface winds were calculated at 85knt(97.8mph), which is therefore Cat2 (96mph+). So they're right in that 105 flight level was cat2 for the storm at that time but it's not based on flight level, it's the ground level speed which just happened to enter Cat2 speed.
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