The Spread Maps Request an invite

Run total + precip rate + MSLP

All maps

Choose a map

Model

ECMWF · Run 18Z 30 Sep · +0 h · Valid Wed 18Z 30 Sep

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

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

9949969981000100210041004100610061006100810081008100810081010101010101010101010101010101010101012101210121012101210121014101410141014101410141014101610161016101610161018101810181018101810201020102010201022L1001H1015H1024L1007H1022H1024

ECMWF · Run 18Z 30 Sep · +0 h · Valid Wed 18Z 30 Sep

Nothing on the map has reached 0.01 in yet · heaviest rate 0.693 in/h at Wed 18Z

One ECMWF run, issued 18Z 30 Sep — played forward 6 hours at a time, from its analysis to 120 hours out.

Methodology

Two of this site's films laid one over the other. Underneath is the Run total: everything this run puts down from its start to each frame, on Tropical Tidbits' scale. On top is the pressure Time lapse: the precipitation falling at that frame's time, on the radar scale, and the sea-level pressure at that time in 2 hPa isobars. So the rate moves on as the film plays and leaves its total behind it. The first frame is the analysis, where the run has put nothing down yet.

The total is a window and the rate and the pressure are instants, all read at the frame's valid time: the total runs from the start of the run to that time. Liquid-equivalent: snow counts as the water it melts to. GFS and ECMWF only, the two models here that publish an instantaneous rate.

Six-hourly to 120 hours. ECMWF's 18Z run forecasts out to 144 hours; this film stops at 120. The frames past the one shown load on demand. 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 the European Centre for Medium-Range Weather Forecasts (ECMWF). 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.

Sources and licences
  • ECMWF: IFS, from ECMWF's open data. This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF). Source: www.ecmwf.int. This ECMWF data is published under a Creative Commons Attribution 4.0 International (CC BY 4.0). ECMWF does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use.

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.