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The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds. An equivalent, more descriptive, definition is "The natural basis for computing passing tropical years is the mean longitude of the Sun reckoned from the precessionally moving equinox (the dynamical equinox or equinox of date).
A tropical cyclone's maximum sustained wind and minimum central air pressure are interlinked and can be used to describe a tropical cyclone's intensity. [ 2 ] [ 3 ] While the maximum winds are more closely related to the destructive potential of a tropical cyclone, it is harder to reliably measure. [ 1 ]
Accumulated cyclone energy is calculated by summing the squares of the estimated maximum sustained velocity of tropical cyclones when wind speeds are at least tropical storm strength (≥ 34 kn; 63 km/h; 39 mph) [4] at recorded six-hour intervals. The sums are usually divided by 10,000 to make them more manageable.
Thus, every 2 to 3 years there is a discrepancy of 22 to 33 days, or a full synodic month. For example, if the winter solstice and the new moon coincide, it takes 19 tropical years for the coincidence to recur. The mathematical logic is this: A tropical year lasts 365.2422 days. [21] a span of 19 tropical years (365.2422 × 19) lasts 6,939.602 days
A year has about 365.24 solar days but 366.24 sidereal days. Therefore, there is one fewer solar day per year than there are sidereal days, similar to an observation of the coin rotation paradox. [5] This makes a sidereal day approximately 365.24 / 366.24 times the length of the 24-hour solar day.
the fraction 1/31 556 925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time. was obtained from the linear time-coefficient in Newcomb's expression for the solar mean longitude (above), taken and applied with the same meaning for the time as in formula (3) above. The relation with Newcomb's coefficient can be seen from:
The NHC and the Central Pacific Hurricane Center assign tropical cyclone intensities in 5 knot increments, and then convert to mph and km/h with a similar rounding for other reports. So an intensity of 115 kn is rated Category 4, but the conversion to miles per hour (132.3 mph) would round down to 130 mph, making it appear to be a Category 3 storm.
the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time. Caesium atomic clocks became operational in 1955, and their use provided further confirmation that the rotation of the earth fluctuated randomly. [ 3 ]