The Spread Maps Request an invite

Absolute PWAT

All maps

GFS · Run 06Z 15 Oct · +0 h · Valid Thu 06Z 15 Oct

Region Southwest

United States

Lower 48 Northwest Southwest Northern Plains Southern Plains Midwest Northeast Mid-Atlantic Southeast

Europe

Europe

The readings under the map are for the whole map, not only the part shown.

GFS · Run 06Z 15 Oct · +0 h · Valid Thu 06Z 15 Oct

Deepest column 62 mm at 20.0N 108.75W

One GFS run, issued 06Z 15 Oct — played forward 6 hours at a time, from the analysis to 384 hours out.

Methodology

PWAT — precipitable water — is how much water vapour the air overhead holds, as the depth of water it would make if it all fell at once.

Six-hourly to 384 hours. GFS forecasts out to 384 hours.

The colours are a depth scale, the same everywhere: the cream band is a depth, not a normal. The same column is deep for Salt Lake City and shallow for Miami, so this map cannot say whether the air is unusual — the Relative to normal chart ranks each place against its own record, and that is the one to read for that.

GFS files this field as PWAT and ECMWF as total column water vapour, the same quantity. Uncorrected model output.

This map is drawn from model output we store ourselves, not from anyone's picture of it, and is based on data and products of NOAA. The per-city read of the same day — which cities the models are fighting about, and what the discussion makes of it — is on the national page. Every model's full forecast for any of these cities, or anywhere else, is in the beta: request an invite; it's free during the beta.

Sources and licences

What we change: each field is cropped to the frame these maps share when we download it, and each map then smooths, contours, differences or ranks those numbers as its Methodology says. These are our maps of the providers' numbers, not their products, and none of them has reviewed or endorsed this site.

Coastlines, borders, lakes and place names: Natural Earth, public domain.