Hurricane reconnaissance

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• Track: the high-density observations (HDOB), one every 30 s: position, flight-level pressure and height, the extrapolated surface pressure (only below the 550 hPa level, as in the format; above it the message carries a D-value instead), temperature, dewpoint, the 30-s flight-level wind and the peak 10-s wind, the SFMR surface wind and rain rate.
• Quality flags: every HDOB line ends with two flags set by the aircraft. A flagged field is removed, not drawn: position (first digit 1 or 3), pressure and height (2 or 3), temperature and dewpoint (second digit 1, 4, 5 or 9), flight-level wind (2, 4, 6, 9) and SFMR (3, 5, 6, 9). Missing values (///) are gaps. On top of that every field has a physical range check, a dewpoint above the temperature is dropped, and a position that jumps more than 650 kt from both neighbours is dropped. Track segments with no valid value of the chosen variable are drawn thin and grey.
• Mission maxima are taken within 300 n mi of the storm centre (interpolated best track), so the ferry legs and the departure airfield do not count.
• Dropsondes (TEMP DROP): the mandatory levels, the significant temperature levels and the 21212 wind levels merged into one profile; heights are integrated from the splash level (the sea surface) and tied to the coded mandatory-level heights. Temperature at a wind-only level is interpolated in log pressure between the neighbouring significant levels (that is what significant levels guarantee). The surface wind estimates follow Franklin et al. (2003): 0.83 times the mean wind in the lowest 150 m (WL150) and 0.80 times the mean of the lowest 500 m (MBL). The skew-T is the sounding explorer itself, with the same analysis.
• Vortex fixes (vortex data messages): the centre position and minimum pressure at the fix time, with the inbound and outbound maximum flight-level winds placed at their bearing and range from the centre.
• Storm: a mission belongs to the storm in its mission number (e.g. 0209A = storm 09); a surveillance mission without one (the NOAA G-IV) is put with the nearest storm and says so. Best track and official forecast: NHC ATCF b-deck and forecast file.
• Freshness: a mirror in GitHub Actions reads the NHC archive every 15 minutes, and again 7 minutes later while a mission is airborne; NHC posts each message a few minutes after it is sent. The page asks for new data every 90 s while a mission is flying.