3-D atmosphere

About this view

• Model and grid. HRDPS (2.5 km model) sampled every 0.1° × 0.16° (about 11 × 10 km), wind every second cell (about 20 km). Heights every 500 ft to 5,000 ft, every 1,000 ft to 12,000 ft, then every 3,000 ft to FL450. Hourly to 24 h, then every 3 h to 48 h. Features smaller than about 25 km or thinner than one level are not resolved.
• Cloud is the model's cloud fraction from humidity (25 % steps), split into low (below 6,500 ft), mid (6,500-20,000 ft) and high (above 20,000 ft) decks by height above sea level. RH is over water.
• Icing is potential only (0-1); severity is not forecast. Turbulence is a rarity score against the HRDPS climatology for that height band (33 = top 5 %, 50 = top 1 %, 75 = top 0.1 %), not EDR.
• Temperature is the model temperature (0.5 °C steps) and dew-point spread the model T − Td (0.5 °C steps up to 5 °C). Runs built before 15 Nov 2026 have no temperature field: there it is worked out from potential temperature with a standard-atmosphere pressure (about ± 2 °C). Stability and shear are worked out in your browser over at least 2,000 ft (winds are stored to 5 kt and 10°, so thinner layers would be rounding).
• Vertical motion exists only between 850 and 700 hPa (roughly 5,000-10,000 ft): HRDPS publishes omega on those two levels only; between them it is interpolated. Surface weather: gust is the hourly maximum; precipitation and its type are the model's 1-hour totals (type = the largest of rain, snow, freezing rain, ice pellets); the ceiling is a screen from humidity-diagnosed cloud (lowest level with 60 % or more), not the model's ceiling diagnostic; fog is where the HRDPS fog visibility (liquid or ice fog) is under 1 km.
• Weather overlay. Falling precipitation comes from the HRDPS 1-hour precipitation (0.1 mm or more) and its type: rain as thin blue-grey streaks, snow as slow white flakes, freezing rain pink, ice pellets orange. It falls from the model cloud base in that column (lowest level with 50 % cloud or 95 % RH; at least 1,000 ft above the ground) to the model ground, drifting with the model wind about 1,500 ft above the ground. The number of particles is proportional to the model rate (each 1-h class taken at about its middle, e.g. 2-4 mm as 3 mm/h), with the standard classes: rain, freezing rain and ice pellets light under 2.5, moderate 2.5-7.5, heavy over 7.5 mm/h; snow (water equivalent) light under 1, moderate 1-2.5, heavy over 2.5 mm/h (about 1 and 2.5 cm/h of snow). Fall speeds are to scale: rain from the Marshall-Palmer drop sizes, 4-9 m/s (faster and longer streaks when heavier), snow 0.6-1.4 m/s, ice pellets 6-9 m/s; on screen 1 m/s is 0.4 % of the region width per second (time-lapse). Where a view holds more than the particle limit, every area is thinned by the same factor, so relative intensity stays right. Not radar. Fog is the HRDPS fog diagnosis (visibility under 1 km), drawn as a soft layer about 600 ft deep (the depth is not forecast). Runs built before 12Z 15 Nov 2026 have neither.
• Terrain is the HRDPS model ground (25 m steps), smoother than the real ridges. Borders, coast, rivers and lakes: Natural Earth (public domain).
• Trees mark where forest really is: tree cover from the 2020 Land Cover of Canada (Natural Resources Canada, 30 m; contains information licensed under the Open Government Licence - Canada) and, in the United States, the North American Land Cover 2020 30m (Commission for Environmental Cooperation / NALCMS, CC BY 4.0), averaged to about 1 km. Needleleaf, broadleaf and mixed forest are told apart (open taiga woodland counts at 60 %). One tree is drawn per grid slot, kept with the chance given by the forest fraction, so density follows the real cover; the trees are symbols, far larger than real trees, and thin out when far away. Broadleaf trees are bare outside an approximate leaf season (by latitude and the valid date). They bend downwind in the model wind near the ground (the lowest cube level, taken at 80 % as a rough 10 m wind): still when calm, a slight sway near 20 kt, strong bending with gust pulses at 40 kt and more (the hourly gust; runs before 15 Nov 2026 assume gusts 1.4 x the wind).
• Buildings are real footprints from the Open Database of Buildings (Statistics Canada; contains information licensed under the Open Government Licence - Canada) for about 30 major cities, simplified (small buildings as rectangles). They are drawn at true scale (no height exaggeration), standing on the model ground, and fade in when the camera is within about 40 km (20 km on phones) at any region size. Heights are the real ones where the database has them (height or number of floors); elsewhere they are estimated from the footprint size (5 m for a house up to 15 m for a large building), which is most of them.
• Roads come from the National Road Network (Statistics Canada / Natural Resources Canada; Open Government Licence - Canada): freeways, highways and numbered routes at every zoom (simplified in the largest regions), and the city streets of the same cities from about 100 km away. Draped on the model ground, which is smoother than the real terrain.
• Precipitation from far away is drawn as soft curtains (one per raining model cell, from the cloud base to the ground, more opaque for heavier classes) that fade into the individual drops and flakes as you zoom in.
• Frames between model hours are interpolated (motion-estimated), not model output. Cloud, humidity, icing, turbulence and vertical motion are moved along the pattern motion measured between the two hours (or the model wind where a run has no motion data); temperature and wind are blended directly. When paused on a model hour, everything shown and read out is the model hour itself.
• Automated guidance from the HRDPS model, not an official forecast. Times are UTC.