{
 "generated_utc": "2026-08-28T23:26:54Z",
 "gfs_cycle_utc": "2026-08-28T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 477.0,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260828_18Z.geojson.gz"
 },
 "counts": {
  "flights": 19,
  "members": 9,
  "rows": 76590
 },
 "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": 7.11,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": -62.83949,
    "lon": -28.30744,
    "alt_m": 12043.0
   },
   "member_spread_deg": {
    "lat": 21.61,
    "lon": 167.09
   },
   "member_spread_now_deg": {
    "lat": 0.78,
    "lon": 2.56
   },
   "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": 33.3,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 39.326,
    "lon": -75.26689,
    "alt_m": 14401.0
   },
   "member_spread_deg": {
    "lat": 14.95,
    "lon": 340.34
   },
   "member_spread_now_deg": {
    "lat": 8.74,
    "lon": 28.06
   },
   "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": 73.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 20.06524,
    "lon": -103.97964,
    "alt_m": 13160.5
   },
   "member_spread_deg": {
    "lat": 12.51,
    "lon": 31.0
   },
   "member_spread_now_deg": {
    "lat": 10.46,
    "lon": 9.85
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:56:00",
   "seed_lat": 77.64583,
   "seed_lon": -74.79167,
   "seed_alt_m": 12270.0,
   "seed_age_h": 6.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 82.71303,
    "lon": 7.36215,
    "alt_m": 11720.1
   },
   "member_spread_deg": {
    "lat": 20.46,
    "lon": 260.22
   },
   "member_spread_now_deg": {
    "lat": 1.47,
    "lon": 12.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 19:07:00",
   "seed_lat": 45.75,
   "seed_lon": -44.625,
   "seed_alt_m": 13360.0,
   "seed_age_h": 4.22,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 18:30:00",
    "lat": 54.01047,
    "lon": 128.59713,
    "alt_m": 13317.2
   },
   "member_spread_deg": {
    "lat": 14.76,
    "lon": 98.83
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 1.66
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 11:53:00",
   "seed_lat": 76.5,
   "seed_lon": 46.625,
   "seed_alt_m": 11980.0,
   "seed_age_h": 11.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 58.53151,
    "lon": 152.37826,
    "alt_m": 12299.0
   },
   "member_spread_deg": {
    "lat": 39.17,
    "lon": 81.43
   },
   "member_spread_now_deg": {
    "lat": 3.2,
    "lon": 1.1
   },
   "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": 105.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 46.00205,
    "lon": 139.8188,
    "alt_m": 12905.5
   },
   "member_spread_deg": {
    "lat": 32.92,
    "lon": 348.1
   },
   "member_spread_now_deg": {
    "lat": 11.03,
    "lon": 341.12
   },
   "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": 314.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 43.35855,
    "lon": 46.30455,
    "alt_m": 12993.0
   },
   "member_spread_deg": {
    "lat": 54.63,
    "lon": 242.58
   },
   "member_spread_now_deg": {
    "lat": 37.05,
    "lon": 247.1
   },
   "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": 88.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 55.06828,
    "lon": 34.72293,
    "alt_m": 13227.6
   },
   "member_spread_deg": {
    "lat": 20.23,
    "lon": 224.88
   },
   "member_spread_now_deg": {
    "lat": 42.75,
    "lon": 93.45
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 14:29:00",
   "seed_lat": 28.5625,
   "seed_lon": 33.41667,
   "seed_alt_m": 12740.0,
   "seed_age_h": 8.85,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 23.92629,
    "lon": -179.11346,
    "alt_m": 12922.9
   },
   "member_spread_deg": {
    "lat": 37.28,
    "lon": 356.35
   },
   "member_spread_now_deg": {
    "lat": 0.6,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 22:20:00",
   "seed_lat": 27.52083,
   "seed_lon": -161.54167,
   "seed_alt_m": 12940.0,
   "seed_age_h": 1.0,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 21:45:00",
    "lat": 23.81169,
    "lon": -56.23004,
    "alt_m": 13105.3
   },
   "member_spread_deg": {
    "lat": 7.47,
    "lon": 53.62
   },
   "member_spread_now_deg": {
    "lat": 0.46,
    "lon": 0.46
   },
   "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": 120.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": 50.63006,
    "lon": 158.58492,
    "alt_m": 12159.9
   },
   "member_spread_deg": {
    "lat": 37.01,
    "lon": 177.21
   },
   "member_spread_now_deg": {
    "lat": 17.62,
    "lon": 234.11
   },
   "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 22:55:45",
   "seed_lat": 73.22911,
   "seed_lon": -165.20831,
   "seed_alt_m": 12780.0,
   "seed_age_h": 0.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 23:00:00",
    "lat": 60.07637,
    "lon": 6.44331,
    "alt_m": 12848.0
   },
   "member_spread_deg": {
    "lat": 22.36,
    "lon": 42.87
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.08
   },
   "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": 55.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 53.91859,
    "lon": -144.94363,
    "alt_m": 13297.8
   },
   "member_spread_deg": {
    "lat": 17.97,
    "lon": 88.25
   },
   "member_spread_now_deg": {
    "lat": 2.42,
    "lon": 17.99
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 15:08:00",
   "seed_lat": 33.45833,
   "seed_lon": 22.66667,
   "seed_alt_m": 16470.0,
   "seed_age_h": 8.2,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 24.87707,
    "lon": 95.36645,
    "alt_m": 16691.9
   },
   "member_spread_deg": {
    "lat": 43.98,
    "lon": 295.36
   },
   "member_spread_now_deg": {
    "lat": 2.73,
    "lon": 4.83
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 11:11:00",
   "seed_lat": 50.85417,
   "seed_lon": 82.5,
   "seed_alt_m": 13030.0,
   "seed_age_h": 12.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 37.30135,
    "lon": -79.63705,
    "alt_m": 13590.9
   },
   "member_spread_deg": {
    "lat": 21.53,
    "lon": 69.62
   },
   "member_spread_now_deg": {
    "lat": 2.67,
    "lon": 3.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 11:20:23",
   "seed_lat": 45.58328,
   "seed_lon": 27.04169,
   "seed_alt_m": 13540.0,
   "seed_age_h": 11.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": 65.95819,
    "lon": -126.41345,
    "alt_m": 13318.1
   },
   "member_spread_deg": {
    "lat": 35.34,
    "lon": 335.45
   },
   "member_spread_now_deg": {
    "lat": 4.42,
    "lon": 4.68
   },
   "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": 266.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-04 17:30:00",
    "lat": -27.9015,
    "lon": 175.0281,
    "alt_m": 12134.0
   },
   "member_spread_deg": {
    "lat": 23.15,
    "lon": 330.8
   },
   "member_spread_now_deg": {
    "lat": 22.2,
    "lon": 118.35
   },
   "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": 21.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 17:45:00",
    "lat": -9.72863,
    "lon": -66.94758,
    "alt_m": 15590.1
   },
   "member_spread_deg": {
    "lat": 43.76,
    "lon": 204.36
   },
   "member_spread_now_deg": {
    "lat": 6.01,
    "lon": 24.12
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}