** Caution: EXTERNAL Sender ** This is not strictly correct. The National Hurricane Center in their Public Advisories use dual units for distance, speed, and central pressure. However, they only give storm surge and rainfall in Customary units. A partial example from today is quoted below:
SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...33.9N 79.2W ABOUT 20 MI...35 KM NW OF MYRTLE BEACH SOUTH CAROLINA MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...N OR 350 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...982 MB...29.00 INCHES The National Weather Service offers point forecasts for a zip code or street address in either Customary or SI units. A link near the bottom of the page allows you to switch. However, their primary concern is aviation weather and US METAR (current aviation weather observations) use primarily Customary measure, in Hg for atmospheric pressure and setting Kollsman window in altimeter (below 18000 feet). Only air temperature and dew point are metric. On Friday, September 30, 2022 at 05:52:29 PM EDT, [email protected] <[email protected]> wrote: ** Caution: EXTERNAL Sender ** Posted on The Rocketry Forum (not by me): "First, I will get to the point. During a hurricane, the National Weather Service (NWS) uses an efficient and intuitive metric measurement of atmospheric pressure . millibars. After the hurricane passes, the NWS reverts to using the inefficient and nonintuitive foot-pound measurement of inches of mercury. Why? As my TRF username suggests, I support using the metric system, including for measuring weather conditions. Unfortunately the National Weather Service does not report weather conditions using metric units. Doing so would go a long way towards metrication. Interestingly, however, the NWS does use one metric unit when it reports atmospheric pressure during a hurricane. Namely, it uses millibars (abbreviated mbar). Incidentally, one millibar exactly equals one hectopascal (hPA), which equals one-tenth of a kilopascal (kPa). Internationally, hectopascals and kilopascals are used to report atmospheric pressure. The International Bureau of Weights and Measures (BIPM, from the French wording) . the international agency charged with administering the metric system on a day-to-day basis . fully approves using hectopascals or kilopascals to measure atmospheric pressure. Nevertheless, since 1 mbar exactly equals 1 hPa, we can consider the millibar to be an approved metric unit. Here is why the millibar is efficient and intuitive. Normal atmospheric pressure at sea level measures 1013.25 mbar (this is a very close approximation). This is not exactly 1000 mbar, of course, but it is so close that you can get a quick sense of atmospheric pressure. If the pressure is less than 1000 mbar, we have a low-pressure situation. If the pressure is greater than 1000 mbar, we have a high-pressure situation. Beautiful and lovely! And here is why inches of mercury (inHg) is inefficient and nonintuitive. Normal atmospheric pressure at sea level measures 29.92 inHg, rounding to two decimal places. Wait! What? Who can remember this? What a ridiculous and useless unit of measurement. But the NWS, following the stubborn and foolish American refusal to adopt the metric system, uses inches of mercury . except during a hurricane. During a hurricane, the NWS uses millibars. Good for them. But once the hurricane passes, the NWS reverts to inches of mercury. Why, pray tell? Since the United States steadfastly refuses to adopt the metric system and instead persists in using the foot-pound system, the NWS.s decision to use a foot-pound measurement for atmospheric pressure makes sense. The NWS is consistent in its measurement backwardness. Asking the NWS to use the metric system would be tantamount to asking it to part the Red Sea. Amazingly, however, during a hurricane the NWS does use the metric system to measure atmospheric pressure, which makes comprehending the strength of the hurricane so much easier. So, then, I ask the question. Since the NWS already makes this concession to modernity . during a hurricane it measures atmospheric pressure using the metric system . why does it revert to the foot-pound system once the hurricane passes? Does anyone know? Thank you for thinking about this. Stanley" _______________________________________________ USMA mailing list [email protected]<mailto:[email protected]> https://lists.colostate.edu/cgi-bin/mailman/listinfo/usma
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