{
 "generated_utc": "2026-09-15T11:26:29Z",
 "gfs_cycle_utc": "2026-09-15T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 453.5,
  "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_20260915_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260915_06Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 66528
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 10:41:18",
   "seed_lat": 36.83333,
   "seed_lon": -16.33333,
   "seed_alt_m": 14460.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 10:45:00",
    "lat": 47.83951,
    "lon": 59.37524,
    "alt_m": 13971.0
   },
   "member_spread_deg": {
    "lat": 15.16,
    "lon": 136.94
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.25
   },
   "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": 246.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 05:45:00",
    "lat": 54.76046,
    "lon": 32.01317,
    "alt_m": 12057.1
   },
   "member_spread_deg": {
    "lat": 39.81,
    "lon": 228.38
   },
   "member_spread_now_deg": {
    "lat": 31.5,
    "lon": 292.36
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-14 18:27:00",
   "seed_lat": 30.9375,
   "seed_lon": -31.70833,
   "seed_alt_m": 13420.0,
   "seed_age_h": 16.88,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 38.9262,
    "lon": -12.3686,
    "alt_m": 13553.2
   },
   "member_spread_deg": {
    "lat": 29.94,
    "lon": 117.42
   },
   "member_spread_now_deg": {
    "lat": 5.28,
    "lon": 3.71
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 08:41:00",
   "seed_lat": 42.3125,
   "seed_lon": -3.29167,
   "seed_alt_m": 13890.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 08:15:00",
    "lat": 46.71413,
    "lon": 134.0642,
    "alt_m": 13190.7
   },
   "member_spread_deg": {
    "lat": 22.55,
    "lon": 127.33
   },
   "member_spread_now_deg": {
    "lat": 1.2,
    "lon": 0.97
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 237.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": -29.90697,
    "lon": -70.1275,
    "alt_m": 14184.6
   },
   "member_spread_deg": {
    "lat": 89.11,
    "lon": 329.32
   },
   "member_spread_now_deg": {
    "lat": 38.15,
    "lon": 144.37
   },
   "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": 125.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 17.26804,
    "lon": -54.58304,
    "alt_m": 12795.9
   },
   "member_spread_deg": {
    "lat": 37.68,
    "lon": 251.15
   },
   "member_spread_now_deg": {
    "lat": 23.1,
    "lon": 180.73
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 291.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 31.92875,
    "lon": -135.22781,
    "alt_m": 12818.6
   },
   "member_spread_deg": {
    "lat": 43.94,
    "lon": 292.63
   },
   "member_spread_now_deg": {
    "lat": 26.85,
    "lon": 294.68
   },
   "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": 77.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 63.49934,
    "lon": 56.65575,
    "alt_m": 12626.3
   },
   "member_spread_deg": {
    "lat": 25.45,
    "lon": 182.44
   },
   "member_spread_now_deg": {
    "lat": 4.32,
    "lon": 24.27
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "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": 46.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 59.04025,
    "lon": -83.95236,
    "alt_m": 12638.5
   },
   "member_spread_deg": {
    "lat": 24.4,
    "lon": 85.03
   },
   "member_spread_now_deg": {
    "lat": 6.36,
    "lon": 16.21
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-14 20:45:45",
   "seed_lat": 65.83328,
   "seed_lon": -74.24998,
   "seed_alt_m": 12720.0,
   "seed_age_h": 14.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:45:00",
    "lat": 50.02637,
    "lon": -167.51408,
    "alt_m": 12989.3
   },
   "member_spread_deg": {
    "lat": 20.93,
    "lon": 290.49
   },
   "member_spread_now_deg": {
    "lat": 1.19,
    "lon": 7.21
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 10:31:00",
   "seed_lat": 32.9375,
   "seed_lon": -7.95833,
   "seed_alt_m": 13380.0,
   "seed_age_h": 0.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 10:00:00",
    "lat": 43.98161,
    "lon": 109.8538,
    "alt_m": 12947.4
   },
   "member_spread_deg": {
    "lat": 13.39,
    "lon": 51.58
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-14 22:03:00",
   "seed_lat": 46.5,
   "seed_lon": -94.625,
   "seed_alt_m": 15880.0,
   "seed_age_h": 13.28,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 62.57474,
    "lon": 44.54473,
    "alt_m": 15382.6
   },
   "member_spread_deg": {
    "lat": 64.78,
    "lon": 140.51
   },
   "member_spread_now_deg": {
    "lat": 6.45,
    "lon": 10.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 05:26:00",
   "seed_lat": 49.72917,
   "seed_lon": 93.75,
   "seed_alt_m": 13210.0,
   "seed_age_h": 5.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 46.13898,
    "lon": -34.19679,
    "alt_m": 13098.3
   },
   "member_spread_deg": {
    "lat": 17.39,
    "lon": 96.83
   },
   "member_spread_now_deg": {
    "lat": 0.89,
    "lon": 3.76
   },
   "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": 157.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 05:30:00",
    "lat": 45.94679,
    "lon": -64.41746,
    "alt_m": 13033.8
   },
   "member_spread_deg": {
    "lat": 32.29,
    "lon": 344.62
   },
   "member_spread_now_deg": {
    "lat": 33.11,
    "lon": 97.34
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 09:51:00",
   "seed_lat": -14.79167,
   "seed_lon": 93.66667,
   "seed_alt_m": 15780.0,
   "seed_age_h": 1.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 09:15:00",
    "lat": -8.2811,
    "lon": 174.07967,
    "alt_m": 15855.6
   },
   "member_spread_deg": {
    "lat": 37.37,
    "lon": 348.29
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 0.56
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}