Sydney Weather Service: Purpose and Scope
Sydney Weather (sydneyweather.au) is a meteorological information service dedicated to the Greater Sydney metropolitan area in New South Wales, Australia. The service aggregates forecast data from the Australian Bureau of Meteorology (BOM) and presents daily 7-day outlooks for eight suburbs spanning Sydney's 12,368 km² metropolitan footprint. The eight forecast zones cover Sydney CBD, Penrith, Liverpool, Parramatta, Campbelltown, Richmond, Bondi, and Manly—a selection representing the full east-west coastal-to-inland gradient of 70 km and the north-south spread of the metropolitan area.
Sydney Weather Forecast Data: Sources and Variables
All meteorological data originates from the Australian Bureau of Meteorology, the Commonwealth agency established under the Meteorology Act 1955. The BOM operates 17 automatic weather stations across Greater Sydney and maintains the Terrey Hills Doppler radar (station 71032) for precipitation tracking.
Each forecast includes six variables per day:
| Forecast Variable | Unit | Source Instrument | Update Frequency |
|---|---|---|---|
| Minimum Temperature | °C | Platinum resistance thermometer (AWS) | 1-minute intervals |
| Maximum Temperature | °C | Platinum resistance thermometer (AWS) | 1-minute intervals |
| Precipitation Probability | Percentage (0-100%) | Ensemble NWP model output | Daily |
| UV Index | UV Index scale (0-14+) | ARPANSA UV monitoring network | Daily |
| Fire Danger Rating | FFDI-derived category | BOM/NSW RFS joint calculation | Daily (fire season) |
| Weather Condition | Classification (6 categories) | Synoptic analysis + NWP | Daily |
The forecast data pipeline executes daily at 6:00 AM AEST via automated retrieval from the BOM's public API endpoints. A redundancy system uses three independent fetch mechanisms: scheduled server-side retrieval, Vercel cron job, and external cron service. Backup data files preserve the previous valid forecast to ensure continuity during API outages.
Sydney's Geographic and Climatic Context
Sydney occupies a coastal basin bounded by the Tasman Sea to the east, the Blue Mountains (part of the Great Dividing Range) to the west, the Hawkesbury River system to the north, and the Royal National Park to the south. This geography produces five distinct microclimate zones within the metropolitan boundary. The East Australian Current (EAC), a warm western boundary current of the South Pacific subtropical gyre, flows southward along the coast at 2-4 knots and maintains sea surface temperatures of 18-24°C year-round, moderating coastal air temperatures by 3-8°C compared to inland locations at equivalent latitude.
Under the Köppen climate classification system, Sydney is classified as Cfa (humid subtropical). The city records a mean annual temperature of 18.4°C, mean annual rainfall of 1,213 mm distributed across 138 rain days, and 2,468 hours of annual sunshine. These values place Sydney in the same climate category as Buenos Aires, Shanghai, and Brisbane.
Sydney Weather Forecast Coverage: Metropolitan Stations
| Forecast Location | BOM Station | Latitude | Longitude | Elevation (m) | Distance from Coast (km) |
|---|---|---|---|---|---|
| Sydney CBD | Observatory Hill (066062) | -33.86 | 151.21 | 39 | 3 |
| Penrith | Penrith Lakes AWS (067113) | -33.72 | 150.68 | 25 | 55 |
| Parramatta | Parramatta North (066124) | -33.80 | 151.00 | 55 | 25 |
| Liverpool | Liverpool (066137) | -33.93 | 150.91 | 20 | 30 |
| Campbelltown | Campbelltown (068257) | -34.06 | 150.78 | 110 | 35 |
| Richmond | Richmond RAAF (067105) | -33.60 | 150.78 | 19 | 60 |
| Bondi | Bondi (nearest: Randwick) | -33.89 | 151.27 | 5 | 0 |
| Manly | Manly (nearest: North Head) | -33.80 | 151.29 | 10 | 0 |
Numerical Weather Prediction: How Sydney Forecasts Are Generated
The Bureau of Meteorology generates Sydney forecasts using the ACCESS (Australian Community Climate and Earth-System Simulator) numerical weather prediction model. ACCESS operates at three spatial resolutions: ACCESS-G (global, 25 km grid), ACCESS-R (regional, 12 km grid), and ACCESS-C (city-scale, 4 km grid for the Sydney domain). The city-scale ACCESS-C model resolves convective processes that drive afternoon thunderstorms, sea breeze dynamics, and terrain-induced rainfall patterns across the Sydney basin.
Forecast production involves four stages: observation ingestion (from AWS, radiosondes, satellite, radar, and aircraft), data assimilation (4D-Var variational analysis), model integration (solving atmospheric primitive equations forward in time), and post-processing (statistical calibration against historical station observations). The BOM's Regional Forecasting Centre in Darling Island, Sydney, adds human meteorologist interpretation to produce the final public forecast products.
Weather Forecast Accuracy: Lead Time and Confidence Intervals
| Forecast Lead Time | Temperature Accuracy (±°C) | Rain Probability Reliability | Condition Accuracy |
|---|---|---|---|
| Day 1 (Today) | ±1.5°C | ~85% | ~90% |
| Day 2 (Tomorrow) | ±2.0°C | ~80% | ~85% |
| Day 3-4 | ±2.5-3.0°C | ~70-75% | ~75% |
| Day 5-6 | ±3.5-4.0°C | ~60-65% | ~65% |
| Day 7 | ±4.0-5.0°C | ~55-60% | ~60% |
These accuracy figures reflect BOM verification statistics for the Sydney metropolitan forecast district. Accuracy is higher during stable anticyclonic (high pressure) conditions and lower during transitional weather patterns involving East Coast Lows, frontal passages, and convective (thunderstorm) environments.
Contact and Additional Resources
Submit questions, data issue reports, or feedback via the contact page. The Sydney Weather Blog provides extended articles on Sydney's climate classification, seasonal patterns, severe weather preparedness, and meteorological phenomena affecting the metropolitan area.