{
 "generated_utc": "2026-09-20T05:26:11Z",
 "gfs_cycle_utc": "2026-09-20T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 434.0,
  "output_interval_min": 30,
  "integration_step_s": 900,
  "wind_field_interval_h": 3
 },
 "staleness": {
  "fresh_seed_max_h": 24.0,
  "served_until_h": 336.0,
  "track_max_age_h": 72.0,
  "region_spread_deg": 60.0,
  "note": "A trajectory is served for 336 h after the last real fix and then the flight disappears. That matches the archive's own bridging limit: 23% of flights go quiet for over a week and are then heard again, so a shorter window drops balloons that are still flying. Past dead_reckoned flights the balloon has not been heard from since seed_time, so its present position is a prediction too -- the silent period is reconstructed from GFS analyses of weather that has already happened, which is why wind_source distinguishes analysis from forecast. Use display_as, not seed_age_h, to decide how to draw a flight: 'track' means the members still agree and a line is meaningful, 'region' means draw the member envelope instead because the nominal member is no better than any other."
 },
 "members": {
  "offsets_m": [
   -2000,
   -1500,
   -1000,
   -500,
   0,
   500,
   1000,
   1500,
   2000
  ],
  "nominal_offset_m": 0,
  "note": "Each member is seeded at the last observed altitude plus its offset and then conserves the density it started with. The ladder is a sensitivity fan, not a probability distribution: adjacent members diverge by roughly 1,200 km over seven days. levels_spanned reports how many GFS levels the fan actually straddles, usually 2 or 3."
 },
 "files": {
  "trajectories_csv_gz": "PBA_forecast_20260920_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260920_00Z.geojson.gz"
 },
 "counts": {
  "flights": 13,
  "members": 9,
  "rows": 55647
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 15:23:18",
   "seed_lat": 40.79167,
   "seed_lon": 19.75,
   "seed_alt_m": 14090.0,
   "seed_age_h": 37.95,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 46.70389,
    "lon": 165.2061,
    "alt_m": 13795.8
   },
   "member_spread_deg": {
    "lat": 30.63,
    "lon": 288.3
   },
   "member_spread_now_deg": {
    "lat": 1.74,
    "lon": 13.88
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 15:11:00",
   "seed_lat": 61.72917,
   "seed_lon": -8.66667,
   "seed_alt_m": 11860.0,
   "seed_age_h": 14.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 23:45:00",
    "lat": 58.44152,
    "lon": 20.03952,
    "alt_m": 12208.9
   },
   "member_spread_deg": {
    "lat": 4.49,
    "lon": 6.28
   },
   "member_spread_now_deg": {
    "lat": 0.5,
    "lon": 2.04
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 13:02:00",
   "seed_lat": 36.66667,
   "seed_lon": 33.58333,
   "seed_alt_m": 13440.0,
   "seed_age_h": 16.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 57.61902,
    "lon": -101.32507,
    "alt_m": 13083.9
   },
   "member_spread_deg": {
    "lat": 22.0,
    "lon": 20.42
   },
   "member_spread_now_deg": {
    "lat": 1.58,
    "lon": 3.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 04:26:00",
   "seed_lat": 46.64583,
   "seed_lon": 55.875,
   "seed_alt_m": 13510.0,
   "seed_age_h": 0.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 04:00:00",
    "lat": 55.41078,
    "lon": -111.29397,
    "alt_m": 12846.6
   },
   "member_spread_deg": {
    "lat": 19.16,
    "lon": 21.25
   },
   "member_spread_now_deg": {
    "lat": 0.2,
    "lon": 0.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "I1RFQ",
   "flight_id": "I1RFQ_2026-09-06",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 05:25:00",
   "seed_lat": 48.52083,
   "seed_lon": 159.54167,
   "seed_alt_m": 12130.0,
   "seed_age_h": 239.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 25.36738,
    "lon": 46.32299,
    "alt_m": 12636.8
   },
   "member_spread_deg": {
    "lat": 55.05,
    "lon": 335.39
   },
   "member_spread_now_deg": {
    "lat": 40.26,
    "lon": 228.16
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 06:05:00",
   "seed_lat": 45.47917,
   "seed_lon": 159.375,
   "seed_alt_m": 12660.0,
   "seed_age_h": 191.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 45.75926,
    "lon": 116.59184,
    "alt_m": 12576.0
   },
   "member_spread_deg": {
    "lat": 33.74,
    "lon": 256.73
   },
   "member_spread_now_deg": {
    "lat": 22.64,
    "lon": 164.1
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 13:01:00",
   "seed_lat": 42.0625,
   "seed_lon": 28.04167,
   "seed_alt_m": 12700.0,
   "seed_age_h": 160.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 50.42039,
    "lon": 30.30962,
    "alt_m": 12821.4
   },
   "member_spread_deg": {
    "lat": 37.98,
    "lon": 184.49
   },
   "member_spread_now_deg": {
    "lat": 21.04,
    "lon": 39.37
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 04:20:45",
   "seed_lat": 71.68745,
   "seed_lon": 168.25002,
   "seed_alt_m": 12840.0,
   "seed_age_h": 0.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 03:45:00",
    "lat": 64.469,
    "lon": -40.80092,
    "alt_m": 12658.0
   },
   "member_spread_deg": {
    "lat": 16.22,
    "lon": 121.29
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 04:51:00",
   "seed_lat": 37.85417,
   "seed_lon": 75.125,
   "seed_alt_m": 13060.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 04:45:00",
    "lat": 35.32057,
    "lon": -99.43895,
    "alt_m": 13239.2
   },
   "member_spread_deg": {
    "lat": 29.34,
    "lon": 323.75
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.06
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 13:15:00",
   "seed_lat": 61.22917,
   "seed_lon": 21.16667,
   "seed_alt_m": 15200.0,
   "seed_age_h": 16.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:45:00",
    "lat": 45.02711,
    "lon": 140.13654,
    "alt_m": 15262.7
   },
   "member_spread_deg": {
    "lat": 7.45,
    "lon": 23.53
   },
   "member_spread_now_deg": {
    "lat": 1.0,
    "lon": 8.67
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 22:51:00",
   "seed_lat": 57.10417,
   "seed_lon": -127.375,
   "seed_alt_m": 12870.0,
   "seed_age_h": 6.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:45:00",
    "lat": 49.36932,
    "lon": 138.02423,
    "alt_m": 12543.7
   },
   "member_spread_deg": {
    "lat": 36.04,
    "lon": 134.49
   },
   "member_spread_now_deg": {
    "lat": 2.53,
    "lon": 1.95
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-08 21:35:23",
   "seed_lat": 52.33328,
   "seed_lon": -95.95831,
   "seed_alt_m": 12860.0,
   "seed_age_h": 271.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:30:00",
    "lat": 51.81642,
    "lon": -3.05852,
    "alt_m": 12941.0
   },
   "member_spread_deg": {
    "lat": 48.77,
    "lon": 282.18
   },
   "member_spread_now_deg": {
    "lat": 48.09,
    "lon": 337.65
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 03:36:00",
   "seed_lat": -15.41667,
   "seed_lon": 153.08333,
   "seed_alt_m": 15910.0,
   "seed_age_h": 1.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-27 03:00:00",
    "lat": -28.90832,
    "lon": -134.8006,
    "alt_m": 15574.8
   },
   "member_spread_deg": {
    "lat": 14.95,
    "lon": 317.66
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}