Analog analysis · all of Canada · 1979 to today
Atmospheric fingerprint
How to use this page · tap any ? for a full explanation
- The big map is today's atmosphere, shown as departures from normal for the date (blue = lower or colder or drier than normal, red = higher, warmer or moister). Pick the field under Map shading.
- Pick a region (Canada overview, five western and five eastern regions). Each region has its own fingerprint: the shape of today's pattern around it, plus eight numbers that describe its air mass and winds.
- Closest analogs are the past 00Z/12Z maps since 1979 that looked most like today, at the same time of year. Click one to see it on the big map and compare.
- Pick an airport to see what actually happened there in those analogs: snow, freezing precipitation, IFR, fog, strong gusts, temperatures; and how often each happened compared with any day at this time of year.
- Model error in analogs shows whether the RAP model tended to run too warm or too cold, too windy or too calm, in these kinds of situations (recent years only).
- How unusual ranks today's pattern against 47 years of maps for the same part of the year.
New here? Start with what an atmospheric fingerprint is, then why analogs are guidance and not a forecast. Words are explained in the glossary at the bottom.
Region
Map shading
Airport
How unusual is today?
Regional fingerprint
Marker = percentile for this time of year (±30 days, 1979–2025).
Unusualness by region
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All of Canada today
One card per region: how unusual today's pattern is there, the closest analog, and what happened at the region's main airport in the 20 closest analogs (vs any day at this time of year). Click a card to open the region.
Closest analogs: 500 hPa height anomaly
Click an analog to show it on the big map. Contours: 500 hPa height every 6 dam.
What happened in the analogs
Bar = share of analogs with the event in the 24 h after the analog time. Black tick = how often it happens on any day in this window of the year.
Model error in analog situations
RAP forecasts (3–12 h leads) from our reforecast archive against the airport's reports, 3–24 h after each analog time. The archive starts in 2021, so only recent analogs count; a handful of cases is a hint, not a statistic.
Analog list
Outcome chips: Heavy snowSnowFreezing precipIFRFogGust 35 kt+Precipquiet
| # | Date (UTC) | Match | What happened (next 24 h) | Max / min | Peak gust | RAP T bias |
|---|
How the fingerprint works
Each 00Z and 12Z since 1979 is described by standardized anomalies (departure from the 1991–2020 normal for that day and hour, divided by the usual spread) of 500 hPa height, sea-level pressure, 850 hPa temperature, precipitable water, 700 hPa humidity and 250 hPa wind over a box around the region, reduced to its 15 leading patterns (EOFs). Eight regional numbers are added: 850 hPa temperature, 1000–500 hPa thickness, precipitable water, vertical totals (stability), low-level and upper jet speed, 700 hPa humidity and sea-level pressure. Analogs are the closest past times in that space, at the same hour, within ±30 days of today's date, at least 5 days apart. "Match" is the pattern correlation of the two anomaly maps. "How unusual" ranks today's distance from normal among all times in the same part of the year.
Today's pattern is the latest ECMWF analysis (F000), averaged onto the reanalysis 2.5° grid. Airport outcomes come from the hourly reports in our climate archive (METAR, and NOAA ISD before ~1998); hours are scaled to 24 when a day has gaps, and days with fewer than 12 reports are left out.
Glossary: words used on this page
See the site glossary.