{
 "generated_utc": "2026-09-18T17:26:43Z",
 "gfs_cycle_utc": "2026-09-18T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 478.0,
  "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_20260918_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260918_12Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 62037
 },
 "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": 1.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 15:00:00",
    "lat": 45.31408,
    "lon": 105.29211,
    "alt_m": 13831.7
   },
   "member_spread_deg": {
    "lat": 17.78,
    "lon": 295.8
   },
   "member_spread_now_deg": {
    "lat": 0.17,
    "lon": 0.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 16:01:00",
   "seed_lat": 58.9375,
   "seed_lon": -35.25,
   "seed_alt_m": 11880.0,
   "seed_age_h": 1.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 16:00:00",
    "lat": 52.24472,
    "lon": 121.72331,
    "alt_m": 12348.9
   },
   "member_spread_deg": {
    "lat": 34.85,
    "lon": 321.83
   },
   "member_spread_now_deg": {
    "lat": 0.28,
    "lon": 0.19
   },
   "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": 3.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 13:15:00",
    "lat": 48.96844,
    "lon": -128.00099,
    "alt_m": 13125.3
   },
   "member_spread_deg": {
    "lat": 14.26,
    "lon": 42.41
   },
   "member_spread_now_deg": {
    "lat": 0.84,
    "lon": 0.78
   },
   "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": 33.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 55.63649,
    "lon": -131.57846,
    "alt_m": 13174.9
   },
   "member_spread_deg": {
    "lat": 31.72,
    "lon": 44.03
   },
   "member_spread_now_deg": {
    "lat": 17.56,
    "lon": 6.23
   },
   "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": 315.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 2.43705,
    "lon": 122.02979,
    "alt_m": 14627.9
   },
   "member_spread_deg": {
    "lat": 56.83,
    "lon": 269.56
   },
   "member_spread_now_deg": {
    "lat": 50.82,
    "lon": 349.38
   },
   "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": 203.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 21.96021,
    "lon": -48.46078,
    "alt_m": 12778.5
   },
   "member_spread_deg": {
    "lat": 26.55,
    "lon": 244.39
   },
   "member_spread_now_deg": {
    "lat": 33.08,
    "lon": 181.99
   },
   "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": 155.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 45.25762,
    "lon": 83.94352,
    "alt_m": 12531.1
   },
   "member_spread_deg": {
    "lat": 40.03,
    "lon": 255.97
   },
   "member_spread_now_deg": {
    "lat": 17.63,
    "lon": 100.31
   },
   "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": 124.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 45.07692,
    "lon": 32.52804,
    "alt_m": 12556.1
   },
   "member_spread_deg": {
    "lat": 34.28,
    "lon": 149.78
   },
   "member_spread_now_deg": {
    "lat": 8.41,
    "lon": 355.36
   },
   "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": 48.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 58.86748,
    "lon": -62.93764,
    "alt_m": 12858.5
   },
   "member_spread_deg": {
    "lat": 12.87,
    "lon": 141.04
   },
   "member_spread_now_deg": {
    "lat": 2.47,
    "lon": 88.82
   },
   "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": 5.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:45:00",
    "lat": 27.77551,
    "lon": -162.64568,
    "alt_m": 13506.7
   },
   "member_spread_deg": {
    "lat": 34.08,
    "lon": 335.99
   },
   "member_spread_now_deg": {
    "lat": 1.61,
    "lon": 1.06
   },
   "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": 2.28,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 14:30:00",
    "lat": 51.06092,
    "lon": 129.62823,
    "alt_m": 15121.3
   },
   "member_spread_deg": {
    "lat": 15.72,
    "lon": 51.76
   },
   "member_spread_now_deg": {
    "lat": 0.17,
    "lon": 1.53
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 05:31:00",
   "seed_lat": 49.22917,
   "seed_lon": 158.25,
   "seed_alt_m": 13130.0,
   "seed_age_h": 11.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 66.44613,
    "lon": 71.71551,
    "alt_m": 12568.6
   },
   "member_spread_deg": {
    "lat": 32.54,
    "lon": 113.39
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 358.79
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 235.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:30:00",
    "lat": 37.98526,
    "lon": -76.55897,
    "alt_m": 13147.9
   },
   "member_spread_deg": {
    "lat": 43.48,
    "lon": 252.19
   },
   "member_spread_now_deg": {
    "lat": 39.12,
    "lon": 252.24
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 05:11:00",
   "seed_lat": -37.10417,
   "seed_lon": 130.04167,
   "seed_alt_m": 15380.0,
   "seed_age_h": 12.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 11:45:00",
    "lat": -21.13093,
    "lon": -172.51719,
    "alt_m": 15514.2
   },
   "member_spread_deg": {
    "lat": 22.43,
    "lon": 56.01
   },
   "member_spread_now_deg": {
    "lat": 3.17,
    "lon": 5.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}