{
 "generated_utc": "2026-09-15T17:26:45Z",
 "gfs_cycle_utc": "2026-09-15T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 459.5,
  "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_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260915_12Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 66915
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:29:48",
   "seed_lat": 36.5625,
   "seed_lon": -13.75,
   "seed_alt_m": 14440.0,
   "seed_age_h": 0.84,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 16:00:00",
    "lat": 47.73118,
    "lon": 65.3689,
    "alt_m": 13931.3
   },
   "member_spread_deg": {
    "lat": 10.3,
    "lon": 146.76
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 0.44
   },
   "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": 252.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 11:45:00",
    "lat": 47.11215,
    "lon": 25.01332,
    "alt_m": 12064.9
   },
   "member_spread_deg": {
    "lat": 40.33,
    "lon": 277.77
   },
   "member_spread_now_deg": {
    "lat": 34.0,
    "lon": 309.62
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:22:00",
   "seed_lat": 26.47917,
   "seed_lon": -32.20833,
   "seed_alt_m": 13450.0,
   "seed_age_h": 0.97,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 15:45:00",
    "lat": 30.70711,
    "lon": -6.78004,
    "alt_m": 13553.1
   },
   "member_spread_deg": {
    "lat": 16.26,
    "lon": 132.74
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 12:21:00",
   "seed_lat": 43.20833,
   "seed_lon": -2.25,
   "seed_alt_m": 13820.0,
   "seed_age_h": 4.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 11:45:00",
    "lat": 43.53932,
    "lon": 115.14404,
    "alt_m": 13387.1
   },
   "member_spread_deg": {
    "lat": 8.29,
    "lon": 110.49
   },
   "member_spread_now_deg": {
    "lat": 2.37,
    "lon": 3.31
   },
   "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": 243.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": -1.54505,
    "lon": -167.63695,
    "alt_m": 14594.5
   },
   "member_spread_deg": {
    "lat": 67.74,
    "lon": 317.81
   },
   "member_spread_now_deg": {
    "lat": 38.03,
    "lon": 143.46
   },
   "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": 131.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 19.40728,
    "lon": -49.77701,
    "alt_m": 12782.7
   },
   "member_spread_deg": {
    "lat": 33.9,
    "lon": 214.93
   },
   "member_spread_now_deg": {
    "lat": 25.2,
    "lon": 178.09
   },
   "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": 297.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 33.06694,
    "lon": -138.44226,
    "alt_m": 12861.6
   },
   "member_spread_deg": {
    "lat": 55.64,
    "lon": 330.43
   },
   "member_spread_now_deg": {
    "lat": 24.18,
    "lon": 291.47
   },
   "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": 83.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 62.80028,
    "lon": 66.06449,
    "alt_m": 12668.7
   },
   "member_spread_deg": {
    "lat": 39.15,
    "lon": 156.44
   },
   "member_spread_now_deg": {
    "lat": 6.92,
    "lon": 24.63
   },
   "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": 52.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 56.2234,
    "lon": -70.24709,
    "alt_m": 12261.2
   },
   "member_spread_deg": {
    "lat": 38.84,
    "lon": 119.24
   },
   "member_spread_now_deg": {
    "lat": 5.8,
    "lon": 16.31
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:55:45",
   "seed_lat": 69.54161,
   "seed_lon": -59.12498,
   "seed_alt_m": 12720.0,
   "seed_age_h": 0.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:00:00",
    "lat": 44.53587,
    "lon": -168.3098,
    "alt_m": 13070.3
   },
   "member_spread_deg": {
    "lat": 28.41,
    "lon": 305.37
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.3
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 15:16:00",
   "seed_lat": 31.60417,
   "seed_lon": -7.08333,
   "seed_alt_m": 13380.0,
   "seed_age_h": 2.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 14:45:00",
    "lat": 44.86427,
    "lon": 131.54295,
    "alt_m": 12873.7
   },
   "member_spread_deg": {
    "lat": 6.88,
    "lon": 25.57
   },
   "member_spread_now_deg": {
    "lat": 0.31,
    "lon": 0.47
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:51:00",
   "seed_lat": 48.35417,
   "seed_lon": -78.45833,
   "seed_alt_m": 15900.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 16:15:00",
    "lat": 47.83185,
    "lon": 41.61918,
    "alt_m": 15531.9
   },
   "member_spread_deg": {
    "lat": 42.41,
    "lon": 75.71
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.5
   },
   "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": 11.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 54.32504,
    "lon": -28.72154,
    "alt_m": 12814.3
   },
   "member_spread_deg": {
    "lat": 26.92,
    "lon": 124.84
   },
   "member_spread_now_deg": {
    "lat": 0.41,
    "lon": 6.48
   },
   "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": 163.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 11:30:00",
    "lat": 63.03294,
    "lon": -77.52893,
    "alt_m": 12782.6
   },
   "member_spread_deg": {
    "lat": 21.38,
    "lon": 323.8
   },
   "member_spread_now_deg": {
    "lat": 33.47,
    "lon": 102.55
   },
   "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": 7.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 11:45:00",
    "lat": -14.10988,
    "lon": -168.67518,
    "alt_m": 15711.0
   },
   "member_spread_deg": {
    "lat": 22.48,
    "lon": 350.3
   },
   "member_spread_now_deg": {
    "lat": 0.9,
    "lon": 2.81
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}