
09-05-2017, 08:25 AM
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A reminder all official storm stats & future path updates come from the US National Hurricane Center (NHC) at or shortly before 2, 5, 8, & 11am/pmEST here (look just below the map on the first page): National Hurricane Center
Current stats are on the left hand side of the Irma section, the "Public Advisory" details storm stats and current watches/Warnings, the "Forecast Discussion" page talks about current state of storm and thoughts on future strength and path thoughts. Media then takes these numbers/info and puts their graphics on them to brand them.
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09-05-2017, 08:46 AM
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6,034 posts, read 3,260,347 times
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An excellent graphic to scale showing those strongest winds are only found right around the eye/center of the storm and less as you go out away from the center:

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09-05-2017, 08:48 AM
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6,034 posts, read 3,260,347 times
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11aEST 5 September 2017: Winds 180mph sustained, higher gust, moving West 14mph, pressure 931mb. A reminder these numbers are verified by active Hurricane recon specialized aircraft from the Air Force and NOAA bravely flying in and around Irma.
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09-05-2017, 09:00 AM
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6,034 posts, read 3,260,347 times
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The official 11amEST 5 September 2017 predicted path of center of storm (cone only represents possible center location of storm out in time, subject to change).
S Florida could feel impacts from Irma as early as daybreak Saturday (subject to change):
Adding NHC key messages:

Last edited by Psychoma; 09-05-2017 at 09:23 AM..
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09-05-2017, 10:09 AM
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34,017 posts, read 54,014,364 times
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Any links to storm surge strength, duration?
A Cat 5 ( hopefully less at landfall but 4 is bad enough) must have a compensatory storm surge...
And maybe not a question for Hurricane savants, but if you follow them you have seen plenty of decisions made about Evacs?
What factors make local Govt/agencies declare mandatory vs voluntary evacuation?
Right now I haven't heard Irma has the potential to produce a drowning rain system like Harvey, but I guess that could change at any time.
Saw mistakes in Houston when notices were too slow or optimistic or ill-informed to choose mandatory initially and then people were trapped by very fast rising water...
And Harvey made quick escalation to Cat4...Irma has not hidden her ferocity...
And if there is better form for that will be happy to go there--but you guys are factual...not emotional...
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09-05-2017, 10:17 AM
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6,034 posts, read 3,260,347 times
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Quick note: Mandatory evacuations announced for VISITORS in the FL Keys beginning daybreak Wednesday.
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09-05-2017, 10:22 AM
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Location: Eastern NC
20,872 posts, read 21,335,011 times
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Got a question concerning pressure. Irma now has 180 mph winds with a pressure of 927mb, why is the pressure so high? Wilma to compare had winds of 185 mph with a pressure of 882. Gilbert also had 185 mph winds with a pressure of 888 mb.
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09-05-2017, 10:33 AM
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9,980 posts, read 10,147,912 times
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Quote:
Originally Posted by trlhiker
Got a question concerning pressure. Irma now has 180 mph winds with a pressure of 927mb, why is the pressure so high? Wilma to compare had winds of 185 mph with a pressure of 882. Gilbert also had 185 mph winds with a pressure of 888 mb.
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SFMR wind of 154 kt was reported, with a few others of 149-150 kt.
Based on these data the initial intensity is set at 155 kt for this
advisory. This makes Irma the strongest hurricane in the Atlantic
basin outside of the Caribbean Sea and Gulf of Mexico in the NHC
records.
Pressure will follow is my guess.
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09-05-2017, 10:56 AM
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Location: Western Massachusetts
46,080 posts, read 48,896,429 times
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Quote:
Originally Posted by trlhiker
Got a question concerning pressure. Irma now has 180 mph winds with a pressure of 927mb, why is the pressure so high? Wilma to compare had winds of 185 mph with a pressure of 882. Gilbert also had 185 mph winds with a pressure of 888 mb.
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winds are created by pressure gradient, as in change in pressure per distance. So if the wind speed is high for the pressure, the pressure must increase fast going out of the eye and therefore the hurricane is small. So at a given pressure (roughly) you can have a large hurricane with relatively low winds but over a larger area or a small hurricane with relatively high winds. Sandy is the opposite case; peak winds were barely above hurricane strength at a pressure of 940 mb, but those moderately high winds were spread over a large area, whipping over more ocean. This made the storm surge reflect a strong closer to its low pressure rather than wind speed.
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09-05-2017, 11:15 AM
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Location: Western Massachusetts
46,080 posts, read 48,896,429 times
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Irma is quite small at the moment but getting bigger...
Irma is expanding in size, and is predicted to increase the radius of its tropical-storm force wind area by about 10 - 15 miles every day. As of 11 am EDT Tuesday, tropical storm-force winds extended out 140 miles from the center, and hurricane-force winds extended out 35 miles from the center. Most of the islands along Irma’s path will be on the weaker left side, where the wind and storm surge impacts will be less than on the right side of the storm.
https://www.wunderground.com/cat6/ca...prclt=DSfCSUna
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