{
 "generated_utc": "2026-09-19T05:26:54Z",
 "gfs_cycle_utc": "2026-09-19T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 490.0,
  "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_20260919_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260919_00Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 64125
 },
 "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": 13.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 42.53103,
    "lon": 134.58333,
    "alt_m": 13758.4
   },
   "member_spread_deg": {
    "lat": 19.0,
    "lon": 339.44
   },
   "member_spread_now_deg": {
    "lat": 1.07,
    "lon": 4.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 18:26:00",
   "seed_lat": 59.27083,
   "seed_lon": -32.58333,
   "seed_alt_m": 11880.0,
   "seed_age_h": 10.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 54.34812,
    "lon": 22.44068,
    "alt_m": 12297.5
   },
   "member_spread_deg": {
    "lat": 22.11,
    "lon": 132.01
   },
   "member_spread_now_deg": {
    "lat": 1.69,
    "lon": 3.0
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 13:47:00",
   "seed_lat": 34.0,
   "seed_lon": 18.33333,
   "seed_alt_m": 13470.0,
   "seed_age_h": 15.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:45:00",
    "lat": 58.48829,
    "lon": -139.59651,
    "alt_m": 12646.3
   },
   "member_spread_deg": {
    "lat": 25.12,
    "lon": 31.61
   },
   "member_spread_now_deg": {
    "lat": 4.2,
    "lon": 1.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 08:01:00",
   "seed_lat": 45.77083,
   "seed_lon": 25.5,
   "seed_alt_m": 13600.0,
   "seed_age_h": 45.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 53.47859,
    "lon": -130.49272,
    "alt_m": 12967.8
   },
   "member_spread_deg": {
    "lat": 39.11,
    "lon": 39.55
   },
   "member_spread_now_deg": {
    "lat": 14.81,
    "lon": 8.56
   },
   "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": 327.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": -3.66537,
    "lon": 133.75102,
    "alt_m": 14628.2
   },
   "member_spread_deg": {
    "lat": 66.54,
    "lon": 271.15
   },
   "member_spread_now_deg": {
    "lat": 55.02,
    "lon": 309.89
   },
   "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": 215.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 23.27275,
    "lon": 16.12293,
    "alt_m": 12690.2
   },
   "member_spread_deg": {
    "lat": 45.24,
    "lon": 249.89
   },
   "member_spread_now_deg": {
    "lat": 37.81,
    "lon": 198.45
   },
   "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": 167.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 43.9512,
    "lon": 89.68384,
    "alt_m": 12548.1
   },
   "member_spread_deg": {
    "lat": 39.28,
    "lon": 219.37
   },
   "member_spread_now_deg": {
    "lat": 21.8,
    "lon": 128.7
   },
   "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": 136.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 42.73484,
    "lon": 15.15664,
    "alt_m": 12543.8
   },
   "member_spread_deg": {
    "lat": 36.96,
    "lon": 135.44
   },
   "member_spread_now_deg": {
    "lat": 11.4,
    "lon": 330.17
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 16:35:45",
   "seed_lat": 76.41661,
   "seed_lon": -30.16665,
   "seed_alt_m": 12780.0,
   "seed_age_h": 60.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 70.54072,
    "lon": -83.63324,
    "alt_m": 12897.0
   },
   "member_spread_deg": {
    "lat": 20.86,
    "lon": 86.8
   },
   "member_spread_now_deg": {
    "lat": 8.78,
    "lon": 95.07
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 11:41:00",
   "seed_lat": 31.47917,
   "seed_lon": 33.29167,
   "seed_alt_m": 13270.0,
   "seed_age_h": 17.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:45:00",
    "lat": 27.31545,
    "lon": -166.41548,
    "alt_m": 13283.0
   },
   "member_spread_deg": {
    "lat": 20.59,
    "lon": 48.15
   },
   "member_spread_now_deg": {
    "lat": 2.31,
    "lon": 5.0
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 15:03:00",
   "seed_lat": 59.375,
   "seed_lon": -0.91667,
   "seed_alt_m": 15270.0,
   "seed_age_h": 14.28,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 52.35586,
    "lon": 148.52537,
    "alt_m": 15122.0
   },
   "member_spread_deg": {
    "lat": 8.11,
    "lon": 38.35
   },
   "member_spread_now_deg": {
    "lat": 1.2,
    "lon": 7.65
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 01:41:00",
   "seed_lat": 48.39583,
   "seed_lon": -161.66667,
   "seed_alt_m": 12640.0,
   "seed_age_h": 3.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 01:15:00",
    "lat": 67.81618,
    "lon": 103.76835,
    "alt_m": 12471.7
   },
   "member_spread_deg": {
    "lat": 37.23,
    "lon": 149.36
   },
   "member_spread_now_deg": {
    "lat": 1.8,
    "lon": 2.23
   },
   "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": 247.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 23:30:00",
    "lat": 48.04004,
    "lon": -38.86333,
    "alt_m": 12939.6
   },
   "member_spread_deg": {
    "lat": 31.94,
    "lon": 276.67
   },
   "member_spread_now_deg": {
    "lat": 38.68,
    "lon": 330.51
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 04:36:00",
   "seed_lat": -25.29167,
   "seed_lon": 151.5,
   "seed_alt_m": 15770.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-26 04:30:00",
    "lat": -15.80659,
    "lon": -178.32361,
    "alt_m": 15890.5
   },
   "member_spread_deg": {
    "lat": 12.45,
    "lon": 357.42
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.15
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}