{
 "generated_utc": "2026-09-01T05:25:03Z",
 "gfs_cycle_utc": "2026-09-01T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 345.5,
  "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_20260901_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260901_00Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 65772
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:13:40",
   "seed_lat": -64.54167,
   "seed_lon": -17.12499,
   "seed_alt_m": 11900.0,
   "seed_age_h": 85.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": -54.06068,
    "lon": 75.42925,
    "alt_m": 12012.2
   },
   "member_spread_deg": {
    "lat": 18.17,
    "lon": 76.22
   },
   "member_spread_now_deg": {
    "lat": 9.25,
    "lon": 112.64
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 23:04:18",
   "seed_lat": 53.97917,
   "seed_lon": 172.375,
   "seed_alt_m": 13860.0,
   "seed_age_h": 6.26,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 32.87636,
    "lon": -64.91569,
    "alt_m": 14450.8
   },
   "member_spread_deg": {
    "lat": 11.93,
    "lon": 68.45
   },
   "member_spread_now_deg": {
    "lat": 1.72,
    "lon": 358.71
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 21:29:00",
   "seed_lat": 33.10417,
   "seed_lon": -84.75,
   "seed_alt_m": 13050.0,
   "seed_age_h": 151.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 19.16045,
    "lon": -90.18713,
    "alt_m": 13174.1
   },
   "member_spread_deg": {
    "lat": 14.83,
    "lon": 76.99
   },
   "member_spread_now_deg": {
    "lat": 15.71,
    "lon": 29.84
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 16:11:00",
   "seed_lat": 61.0,
   "seed_lon": -15.16667,
   "seed_alt_m": 12030.0,
   "seed_age_h": 13.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": 81.62497,
    "lon": 22.85594,
    "alt_m": 11739.0
   },
   "member_spread_deg": {
    "lat": 32.2,
    "lon": 194.54
   },
   "member_spread_now_deg": {
    "lat": 4.32,
    "lon": 11.14
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 15:47:00",
   "seed_lat": 50.16667,
   "seed_lon": 16.875,
   "seed_alt_m": 13220.0,
   "seed_age_h": 37.55,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": 63.14621,
    "lon": -114.0885,
    "alt_m": 13127.9
   },
   "member_spread_deg": {
    "lat": 21.61,
    "lon": 59.45
   },
   "member_spread_now_deg": {
    "lat": 4.04,
    "lon": 5.92
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 19.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 59.5165,
    "lon": 134.13426,
    "alt_m": 11942.3
   },
   "member_spread_deg": {
    "lat": 39.81,
    "lon": 265.24
   },
   "member_spread_now_deg": {
    "lat": 5.06,
    "lon": 11.84
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-24 14:13:00",
   "seed_lat": 65.52083,
   "seed_lon": 37.33333,
   "seed_alt_m": 12490.0,
   "seed_age_h": 183.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": 54.32684,
    "lon": -130.62967,
    "alt_m": 13172.8
   },
   "member_spread_deg": {
    "lat": 28.88,
    "lon": 205.13
   },
   "member_spread_now_deg": {
    "lat": 13.9,
    "lon": 306.34
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 06:33:48",
   "seed_lat": 61.6875,
   "seed_lon": -165.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 166.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 47.13522,
    "lon": 126.41671,
    "alt_m": 13356.5
   },
   "member_spread_deg": {
    "lat": 38.46,
    "lon": 251.84
   },
   "member_spread_now_deg": {
    "lat": 36.11,
    "lon": 222.67
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 04:39:00",
   "seed_lat": 32.08333,
   "seed_lon": 109.54167,
   "seed_alt_m": 12660.0,
   "seed_age_h": 0.68,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 04:45:00",
    "lat": 13.37252,
    "lon": 153.794,
    "alt_m": 12824.6
   },
   "member_spread_deg": {
    "lat": 38.92,
    "lon": 328.41
   },
   "member_spread_now_deg": {
    "lat": 0.08,
    "lon": 0.05
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 22:00:00",
   "seed_lat": 38.02083,
   "seed_lon": -70.91667,
   "seed_alt_m": 13060.0,
   "seed_age_h": 7.33,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 31.09624,
    "lon": -23.67348,
    "alt_m": 13012.8
   },
   "member_spread_deg": {
    "lat": 7.26,
    "lon": 35.03
   },
   "member_spread_now_deg": {
    "lat": 0.66,
    "lon": 1.76
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 11:11:00",
   "seed_lat": 53.6875,
   "seed_lon": 74.70833,
   "seed_alt_m": 12000.0,
   "seed_age_h": 42.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": 67.64896,
    "lon": -170.85631,
    "alt_m": 12213.2
   },
   "member_spread_deg": {
    "lat": 22.36,
    "lon": 150.1
   },
   "member_spread_now_deg": {
    "lat": 4.89,
    "lon": 26.46
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 19:35:45",
   "seed_lat": 76.52078,
   "seed_lon": -54.12498,
   "seed_alt_m": 12900.0,
   "seed_age_h": 9.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": 55.69247,
    "lon": 45.90287,
    "alt_m": 13020.4
   },
   "member_spread_deg": {
    "lat": 16.38,
    "lon": 62.71
   },
   "member_spread_now_deg": {
    "lat": 6.08,
    "lon": 1.73
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KJ4AWK-1",
   "flight_id": "KJ4AWK-1_2026-08-22",
   "payload_type": "APRS",
   "seed_time": "2026-08-26 15:51:36",
   "seed_lat": 41.62025,
   "seed_lon": 25.112,
   "seed_alt_m": 13223.0,
   "seed_age_h": 133.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 23:45:00",
    "lat": 54.01352,
    "lon": -15.22085,
    "alt_m": 13161.9
   },
   "member_spread_deg": {
    "lat": 18.83,
    "lon": 118.24
   },
   "member_spread_now_deg": {
    "lat": 19.57,
    "lon": 339.36
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 04:11:00",
   "seed_lat": 42.16667,
   "seed_lon": 110.75,
   "seed_alt_m": 16040.0,
   "seed_age_h": 1.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 03:45:00",
    "lat": 66.28803,
    "lon": -102.69874,
    "alt_m": 15355.6
   },
   "member_spread_deg": {
    "lat": 42.43,
    "lon": 317.64
   },
   "member_spread_now_deg": {
    "lat": 0.3,
    "lon": 0.74
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 02:21:00",
   "seed_lat": 41.58333,
   "seed_lon": -150.16667,
   "seed_alt_m": 13610.0,
   "seed_age_h": 2.98,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 01:45:00",
    "lat": 53.25381,
    "lon": -22.55149,
    "alt_m": 13010.4
   },
   "member_spread_deg": {
    "lat": 33.26,
    "lon": 112.74
   },
   "member_spread_now_deg": {
    "lat": 0.71,
    "lon": 0.54
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 01:35:23",
   "seed_lat": 49.70828,
   "seed_lon": 105.12502,
   "seed_alt_m": 13420.0,
   "seed_age_h": 3.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 01:00:00",
    "lat": 36.93696,
    "lon": -78.0225,
    "alt_m": 13852.8
   },
   "member_spread_deg": {
    "lat": 46.09,
    "lon": 263.15
   },
   "member_spread_now_deg": {
    "lat": 0.38,
    "lon": 1.47
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 20:01:00",
   "seed_lat": -20.58333,
   "seed_lon": -53.125,
   "seed_alt_m": 15810.0,
   "seed_age_h": 9.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 23:30:00",
    "lat": -28.41733,
    "lon": 19.56037,
    "alt_m": 15564.9
   },
   "member_spread_deg": {
    "lat": 42.01,
    "lon": 74.42
   },
   "member_spread_now_deg": {
    "lat": 3.28,
    "lon": 2.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}