{
 "generated_utc": "2026-09-11T17:26:30Z",
 "gfs_cycle_utc": "2026-09-11T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 433.5,
  "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_20260911_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260911_12Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 61002
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 15:35:48",
   "seed_lat": 41.47917,
   "seed_lon": -16.95833,
   "seed_alt_m": 14600.0,
   "seed_age_h": 1.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 15:00:00",
    "lat": 36.18845,
    "lon": 2.06897,
    "alt_m": 14116.1
   },
   "member_spread_deg": {
    "lat": 15.62,
    "lon": 66.62
   },
   "member_spread_now_deg": {
    "lat": 0.56,
    "lon": 0.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 156.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 11:45:00",
    "lat": 57.55258,
    "lon": -28.56582,
    "alt_m": 11876.5
   },
   "member_spread_deg": {
    "lat": 23.48,
    "lon": 337.22
   },
   "member_spread_now_deg": {
    "lat": 17.62,
    "lon": 156.88
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 16:22:00",
   "seed_lat": 29.39583,
   "seed_lon": -44.66667,
   "seed_alt_m": 13690.0,
   "seed_age_h": 0.97,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 15:45:00",
    "lat": 33.78676,
    "lon": 20.34532,
    "alt_m": 13463.5
   },
   "member_spread_deg": {
    "lat": 10.22,
    "lon": 54.09
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 16:41:00",
   "seed_lat": 51.45833,
   "seed_lon": -92.79167,
   "seed_alt_m": 13270.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 16:45:00",
    "lat": 39.30189,
    "lon": 67.79179,
    "alt_m": 13581.6
   },
   "member_spread_deg": {
    "lat": 21.44,
    "lon": 127.45
   },
   "member_spread_now_deg": {
    "lat": 0.19,
    "lon": 0.57
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 271.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 71.46272,
    "lon": -144.89403,
    "alt_m": 11742.7
   },
   "member_spread_deg": {
    "lat": 51.23,
    "lon": 229.68
   },
   "member_spread_now_deg": {
    "lat": 49.84,
    "lon": 315.29
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 13:31:52",
   "seed_lat": 46.04167,
   "seed_lon": 61.70833,
   "seed_alt_m": 13960.0,
   "seed_age_h": 147.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 29.0263,
    "lon": 156.22866,
    "alt_m": 14513.6
   },
   "member_spread_deg": {
    "lat": 33.66,
    "lon": 148.95
   },
   "member_spread_now_deg": {
    "lat": 27.32,
    "lon": 243.04
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 35.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 22.67703,
    "lon": -57.18226,
    "alt_m": 12817.9
   },
   "member_spread_deg": {
    "lat": 42.95,
    "lon": 219.6
   },
   "member_spread_now_deg": {
    "lat": 9.03,
    "lon": 24.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 08:04:00",
   "seed_lat": 37.27083,
   "seed_lon": 133.375,
   "seed_alt_m": 12750.0,
   "seed_age_h": 201.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 23.26058,
    "lon": 171.14026,
    "alt_m": 12852.6
   },
   "member_spread_deg": {
    "lat": 21.15,
    "lon": 339.48
   },
   "member_spread_now_deg": {
    "lat": 19.36,
    "lon": 321.52
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 09:35:00",
   "seed_lat": 40.4375,
   "seed_lon": 108.79167,
   "seed_alt_m": 12700.0,
   "seed_age_h": 7.75,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 43.88882,
    "lon": -106.08241,
    "alt_m": 12809.7
   },
   "member_spread_deg": {
    "lat": 8.5,
    "lon": 130.26
   },
   "member_spread_now_deg": {
    "lat": 0.74,
    "lon": 3.67
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 12:36:00",
   "seed_lat": 55.875,
   "seed_lon": -6.45833,
   "seed_alt_m": 12800.0,
   "seed_age_h": 4.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 12:00:00",
    "lat": 51.92715,
    "lon": -178.94748,
    "alt_m": 12647.9
   },
   "member_spread_deg": {
    "lat": 10.02,
    "lon": 323.14
   },
   "member_spread_now_deg": {
    "lat": 3.66,
    "lon": 0.85
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 06:50:45",
   "seed_lat": 52.43745,
   "seed_lon": 153.50002,
   "seed_alt_m": 13180.0,
   "seed_age_h": 10.49,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:45:00",
    "lat": 83.71916,
    "lon": 43.34833,
    "alt_m": 12848.3
   },
   "member_spread_deg": {
    "lat": 19.07,
    "lon": 129.27
   },
   "member_spread_now_deg": {
    "lat": 0.31,
    "lon": 7.54
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 02:18:00",
   "seed_lat": 22.95833,
   "seed_lon": -151.54167,
   "seed_alt_m": 16440.0,
   "seed_age_h": 15.03,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:45:00",
    "lat": 50.25979,
    "lon": -4.79524,
    "alt_m": 15715.7
   },
   "member_spread_deg": {
    "lat": 28.46,
    "lon": 344.8
   },
   "member_spread_now_deg": {
    "lat": 7.12,
    "lon": 15.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 15:46:00",
   "seed_lat": 38.6875,
   "seed_lon": 9.54167,
   "seed_alt_m": 13310.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 15:15:00",
    "lat": 50.11852,
    "lon": -176.93246,
    "alt_m": 13063.0
   },
   "member_spread_deg": {
    "lat": 16.02,
    "lon": 32.66
   },
   "member_spread_now_deg": {
    "lat": 0.29,
    "lon": 0.44
   },
   "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": 67.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:30:00",
    "lat": 46.96971,
    "lon": 147.19001,
    "alt_m": 13266.8
   },
   "member_spread_deg": {
    "lat": 28.04,
    "lon": 345.16
   },
   "member_spread_now_deg": {
    "lat": 8.14,
    "lon": 79.42
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 10:51:00",
   "seed_lat": -21.66667,
   "seed_lon": 67.0,
   "seed_alt_m": 15600.0,
   "seed_age_h": 6.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 11:45:00",
    "lat": -26.18271,
    "lon": -175.38833,
    "alt_m": 15522.4
   },
   "member_spread_deg": {
    "lat": 20.98,
    "lon": 342.51
   },
   "member_spread_now_deg": {
    "lat": 2.04,
    "lon": 6.99
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}