{
 "generated_utc": "2026-08-28T11:26:53Z",
 "gfs_cycle_utc": "2026-08-28T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 465.0,
  "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_20260828_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260828_06Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 71982
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-26 23:18:40",
   "seed_lat": -70.79167,
   "seed_lon": -148.58332,
   "seed_alt_m": 12300.0,
   "seed_age_h": 36.02,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": -84.56744,
    "lon": -18.16132,
    "alt_m": 11997.5
   },
   "member_spread_deg": {
    "lat": 25.12,
    "lon": 152.93
   },
   "member_spread_now_deg": {
    "lat": 2.58,
    "lon": 11.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 14:01:48",
   "seed_lat": 43.125,
   "seed_lon": 21.54167,
   "seed_alt_m": 14180.0,
   "seed_age_h": 21.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 61.11677,
    "lon": -106.65858,
    "alt_m": 13839.2
   },
   "member_spread_deg": {
    "lat": 20.71,
    "lon": 331.17
   },
   "member_spread_now_deg": {
    "lat": 4.73,
    "lon": 11.67
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 61.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 28.88088,
    "lon": -99.84074,
    "alt_m": 13075.6
   },
   "member_spread_deg": {
    "lat": 5.47,
    "lon": 36.14
   },
   "member_spread_now_deg": {
    "lat": 7.21,
    "lon": 7.41
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 22:51:00",
   "seed_lat": 69.58333,
   "seed_lon": -114.33333,
   "seed_alt_m": 12310.0,
   "seed_age_h": 12.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": 70.80299,
    "lon": -112.88811,
    "alt_m": 12197.5
   },
   "member_spread_deg": {
    "lat": 32.33,
    "lon": 176.8
   },
   "member_spread_now_deg": {
    "lat": 6.5,
    "lon": 27.03
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 21:37:00",
   "seed_lat": 44.35417,
   "seed_lon": -69.45833,
   "seed_alt_m": 13180.0,
   "seed_age_h": 13.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 50.72328,
    "lon": 120.19148,
    "alt_m": 13210.4
   },
   "member_spread_deg": {
    "lat": 17.64,
    "lon": 171.05
   },
   "member_spread_now_deg": {
    "lat": 0.87,
    "lon": 7.42
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 10:53:00",
   "seed_lat": 76.64583,
   "seed_lon": 46.08333,
   "seed_alt_m": 11980.0,
   "seed_age_h": 0.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 11:00:00",
    "lat": 57.07489,
    "lon": 110.42291,
    "alt_m": 12111.2
   },
   "member_spread_deg": {
    "lat": 32.07,
    "lon": 338.29
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.22
   },
   "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": 93.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": 51.44167,
    "lon": 148.87009,
    "alt_m": 12731.5
   },
   "member_spread_deg": {
    "lat": 30.9,
    "lon": 302.33
   },
   "member_spread_now_deg": {
    "lat": 19.3,
    "lon": 86.04
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-15 20:50:37",
   "seed_lat": 40.97911,
   "seed_lon": -75.41666,
   "seed_alt_m": 13300.0,
   "seed_age_h": 302.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": 41.90688,
    "lon": 30.85643,
    "alt_m": 12954.5
   },
   "member_spread_deg": {
    "lat": 51.25,
    "lon": 280.76
   },
   "member_spread_now_deg": {
    "lat": 45.94,
    "lon": 227.67
   },
   "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": 76.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 48.61167,
    "lon": 24.65716,
    "alt_m": 13453.7
   },
   "member_spread_deg": {
    "lat": 26.98,
    "lon": 160.4
   },
   "member_spread_now_deg": {
    "lat": 39.25,
    "lon": 45.78
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 09:24:00",
   "seed_lat": 28.5,
   "seed_lon": 31.04167,
   "seed_alt_m": 12750.0,
   "seed_age_h": 1.93,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 09:00:00",
    "lat": 35.17823,
    "lon": 160.60589,
    "alt_m": 12878.7
   },
   "member_spread_deg": {
    "lat": 43.7,
    "lon": 351.64
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 04:25:00",
   "seed_lat": 27.08333,
   "seed_lon": -164.41667,
   "seed_alt_m": 12960.0,
   "seed_age_h": 6.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 25.48667,
    "lon": -67.08064,
    "alt_m": 13131.1
   },
   "member_spread_deg": {
    "lat": 6.09,
    "lon": 46.65
   },
   "member_spread_now_deg": {
    "lat": 3.26,
    "lon": 3.29
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-23 23:01:00",
   "seed_lat": 73.33333,
   "seed_lon": -150.25,
   "seed_alt_m": 11900.0,
   "seed_age_h": 108.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 78.09953,
    "lon": 121.68157,
    "alt_m": 12311.2
   },
   "member_spread_deg": {
    "lat": 24.77,
    "lon": 195.87
   },
   "member_spread_now_deg": {
    "lat": 20.73,
    "lon": 227.67
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 04:55:45",
   "seed_lat": 73.18745,
   "seed_lon": 179.45835,
   "seed_alt_m": 12780.0,
   "seed_age_h": 6.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": 63.20176,
    "lon": -3.19207,
    "alt_m": 12928.1
   },
   "member_spread_deg": {
    "lat": 28.13,
    "lon": 203.06
   },
   "member_spread_now_deg": {
    "lat": 1.43,
    "lon": 2.03
   },
   "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": 43.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": 41.02996,
    "lon": -138.59042,
    "alt_m": 13286.4
   },
   "member_spread_deg": {
    "lat": 22.28,
    "lon": 64.24
   },
   "member_spread_now_deg": {
    "lat": 3.04,
    "lon": 17.57
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 10:31:00",
   "seed_lat": 35.22917,
   "seed_lon": 21.375,
   "seed_alt_m": 16400.0,
   "seed_age_h": 0.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 10:00:00",
    "lat": 30.73082,
    "lon": -174.44997,
    "alt_m": 16436.7
   },
   "member_spread_deg": {
    "lat": 29.11,
    "lon": 333.61
   },
   "member_spread_now_deg": {
    "lat": 0.47,
    "lon": 0.72
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 09:46:00",
   "seed_lat": 50.6875,
   "seed_lon": 80.04167,
   "seed_alt_m": 13030.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 09:15:00",
    "lat": 39.71937,
    "lon": -138.28945,
    "alt_m": 13405.3
   },
   "member_spread_deg": {
    "lat": 23.19,
    "lon": 114.18
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.54
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-37",
   "flight_id": "ZS6SRC-37_2026-07-31",
   "payload_type": "WSPR",
   "seed_time": "2026-08-17 20:59:00",
   "seed_lat": -20.58333,
   "seed_lon": -72.33333,
   "seed_alt_m": 12210.0,
   "seed_age_h": 254.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 05:30:00",
    "lat": -32.0293,
    "lon": 175.11774,
    "alt_m": 12118.8
   },
   "member_spread_deg": {
    "lat": 28.64,
    "lon": 351.26
   },
   "member_spread_now_deg": {
    "lat": 16.78,
    "lon": 131.57
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 01:21:00",
   "seed_lat": -25.875,
   "seed_lon": -135.66667,
   "seed_alt_m": 15340.0,
   "seed_age_h": 9.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:45:00",
    "lat": -8.39163,
    "lon": -52.82132,
    "alt_m": 15580.4
   },
   "member_spread_deg": {
    "lat": 44.47,
    "lon": 176.08
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 12.45
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}