{
 "generated_utc": "2026-09-18T23:26:39Z",
 "gfs_cycle_utc": "2026-09-18T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 484.0,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260918_18Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 63072
 },
 "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": 7.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 44.29248,
    "lon": 120.00822,
    "alt_m": 13779.6
   },
   "member_spread_deg": {
    "lat": 35.89,
    "lon": 323.32
   },
   "member_spread_now_deg": {
    "lat": 0.39,
    "lon": 2.64
   },
   "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": 4.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 18:00:00",
    "lat": 48.26833,
    "lon": 25.96042,
    "alt_m": 12291.0
   },
   "member_spread_deg": {
    "lat": 31.3,
    "lon": 276.43
   },
   "member_spread_now_deg": {
    "lat": 0.86,
    "lon": 0.74
   },
   "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": 9.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:45:00",
    "lat": 65.83261,
    "lon": -156.07752,
    "alt_m": 12674.7
   },
   "member_spread_deg": {
    "lat": 19.26,
    "lon": 41.8
   },
   "member_spread_now_deg": {
    "lat": 2.76,
    "lon": 1.0
   },
   "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": 39.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 46.64969,
    "lon": -126.95164,
    "alt_m": 13353.4
   },
   "member_spread_deg": {
    "lat": 44.33,
    "lon": 57.28
   },
   "member_spread_now_deg": {
    "lat": 16.49,
    "lon": 7.29
   },
   "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": 321.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 2.0351,
    "lon": 128.06806,
    "alt_m": 14604.1
   },
   "member_spread_deg": {
    "lat": 54.85,
    "lon": 262.44
   },
   "member_spread_now_deg": {
    "lat": 52.01,
    "lon": 325.11
   },
   "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": 209.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 27.08871,
    "lon": 20.22628,
    "alt_m": 12742.6
   },
   "member_spread_deg": {
    "lat": 52.27,
    "lon": 256.87
   },
   "member_spread_now_deg": {
    "lat": 35.58,
    "lon": 189.47
   },
   "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": 161.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 47.12557,
    "lon": 103.4085,
    "alt_m": 12507.6
   },
   "member_spread_deg": {
    "lat": 28.98,
    "lon": 236.17
   },
   "member_spread_now_deg": {
    "lat": 19.85,
    "lon": 114.22
   },
   "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": 130.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 53.95863,
    "lon": 36.53787,
    "alt_m": 12505.9
   },
   "member_spread_deg": {
    "lat": 30.48,
    "lon": 151.43
   },
   "member_spread_now_deg": {
    "lat": 9.27,
    "lon": 338.85
   },
   "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": 54.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 53.8045,
    "lon": -62.02817,
    "alt_m": 13147.6
   },
   "member_spread_deg": {
    "lat": 20.37,
    "lon": 89.94
   },
   "member_spread_now_deg": {
    "lat": 5.37,
    "lon": 97.56
   },
   "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": 11.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:45:00",
    "lat": 22.40627,
    "lon": -173.60159,
    "alt_m": 13385.4
   },
   "member_spread_deg": {
    "lat": 28.17,
    "lon": 343.48
   },
   "member_spread_now_deg": {
    "lat": 2.38,
    "lon": 2.4
   },
   "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": 8.28,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 50.09269,
    "lon": 129.18265,
    "alt_m": 15188.3
   },
   "member_spread_deg": {
    "lat": 10.5,
    "lon": 26.08
   },
   "member_spread_now_deg": {
    "lat": 0.61,
    "lon": 4.85
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 22:46:00",
   "seed_lat": 47.08333,
   "seed_lon": -167.875,
   "seed_alt_m": 12790.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 22:45:00",
    "lat": 67.26953,
    "lon": 113.65739,
    "alt_m": 12404.5
   },
   "member_spread_deg": {
    "lat": 32.86,
    "lon": 119.01
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.61
   },
   "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": 241.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:30:00",
    "lat": 47.48519,
    "lon": -77.65325,
    "alt_m": 13250.3
   },
   "member_spread_deg": {
    "lat": 41.53,
    "lon": 324.38
   },
   "member_spread_now_deg": {
    "lat": 38.84,
    "lon": 260.75
   },
   "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": 18.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 17:45:00",
    "lat": -24.62571,
    "lon": -161.57588,
    "alt_m": 15437.7
   },
   "member_spread_deg": {
    "lat": 22.72,
    "lon": 31.15
   },
   "member_spread_now_deg": {
    "lat": 5.56,
    "lon": 6.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}