USA_SEAHGT value either 12' or null

[Scott Bruce]

Hi folks,

I'm curious as  to why the column for USA_SEAHGT either contains a value of 12 feet or is empty.  Is this some kind of threshold?  Should it vary?

I can find precious little explaining the nature of this column and it's associated radii columns.

Best regards,

Scott Bruce

[Jennifer Gahtan - NOAA Federal]

Hi Scott,

USA_SEAHGT is the wave height in feet of the seas radii given in USA_SEARAD_NE, USA_SEARAD_SE, USA_SEARAD_SW, and USA_SEARAD_NW. From the original atcf formatted data, this data would be taken from the SEAS variable. A value of 12 feet means that the wave height at which the seas radii are measured is 12 feet and an empty value means no seas radii data are available. Since this is an indicator for the radii, it makes sense that the value is held constant, whereas the radii themselves (USA_SEARAS_XX) are varying. 

Hope this helps,

Jennifer

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Jennifer Gahtan, Ph.D.

Physical Scientist
CSSD
NOAA's National Centers for Environmental Information (NCEI)
151 Patton Ave. Asheville, NC 28801

[Scott Bruce]

Hi Jennifer,

Many thanks for your response and clarification on where the data comes from - that answers part of my question.

The part of this that still mystifies me is that in the IBTrACS data itself, the ONLY value that USA_SEAHGT ever has is either 12' or blank - this remains true from the first occurrence in the 2008 data through to present day.

According to the atcf data description, the SEAS variable should range between 0-99 feet, which seems reasonable, but maybe in practice 12' is the only value that's used?

Spot checking through b-decks files I notice that when SEAS has a value it's usually blank, 0 or 12.  Hardly a comprehensive view into the data but there definitely seems to be a pattern, assuming I'm reading these correctly.

Cheers,

Scott

[Jennifer Gahtan - NOAA Federal]

Hi Scott,

Measurements like radii tend to be chosen at consistent values to allow for standard measurements and intercomparison between storms. While in practice, the 12' height is usually used, since the source data gives the option for multiple values, IBTrACS carries over the variable into USA_SEAHGT, .

-Jennifer

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