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Nerd mode: every forecast, readouts, filters and range & bearing for weather enthusiasts

Storm · Forecast to formNorth America

A new low could form northeast of San Diego on Tuesday night

Los Angeles — Could pass near Los Angeles Thu afternoon; 3 in 10 forecasts bring it within 100 mi.

Updated Mon., Sept. 28, 5:47 p.m. PDT · 91 forecast tracks from NOAA, ECMWF and Environment Canada: medium

This storm is no longer in our active list. This is its last forecast, from the Mon 28 Sep 12Z–18Z runs.

Los Angeles — Could pass near Los Angeles Thu afternoon; 3 in 10 forecasts bring it within 100 mi.

Quick answers

As of the Mon 28 Sep 12Z–18Z model runs · updated Mon., Sept. 28, 5:47 p.m. PDT

Where will the low over California form?
Forecasts that develop it have the centre forming about 100 miles northeast of San Diego, over California on Tuesday night. The most likely path takes it about 140 miles north of Los Angeles by Friday night.
When will the low over California be closest to Los Angeles?
Most likely Thursday, Oct. 1, around 2 p.m. PDT. Across the forecasts the comes between Tue 10 p.m. and Tue 5 a.m. PDT. Most forecasts pass the centre 20–150 miles east of Los Angeles.
What is the chance it passes within 100 miles of Los Angeles?
27%: 3 in 10 forecasts bring the storm’s centre within 100 miles of Los Angeles. Elsewhere: San Diego 24%, Sacramento 20%, San Francisco 19%. Rain, wind and coastal flooding can reach well beyond 100 miles from the centre.
How much rain could Los Angeles get while the low over California passes?
From Mon 5 p.m. (when the forecast’s rain totals start) to Mon 11 a.m. PDT, the end of the forecast, the middle of NOAA’s 31 GEFS forecasts brings almost no rain or melted snow to Los Angeles; fewer than 1 in 10 bring 0.5 in. By Tue 5 p.m., when that window opens, the middle forecast has almost none yet. That is all the rain in that time, not only the low over California’s, from one model (GEFS) on a coarse grid; local official forecasts can differ. Los Angeles: rain and wind this week →
How sure is the forecast?
Path certainty: medium. 91 of 185 show the storm, and they on where it goes.
Do the AI and physics models agree?
Not yet: they differ. Chance within 100 miles of Los Angeles: AI ensembles (AIFS ENS, AIGEFS) 23%, physics ensembles (ECMWF ENS) 65%. By model: ECMWF ENS 65%, AIFS ENS 25%, AIGEFS 19%. By Thursday night the AI ensembles’ middle track is about 160 miles west of the physics ensembles’. Both take it to about 1,002 at its deepest.
Will the low over California become a bomb cyclone?
Unlikely. None of the 185 deepen it fast enough to count as a (a pressure fall of roughly 24 in 24 hours, adjusted for latitude).

New to these maps? Read how to read a spaghetti map, or see the week’s rain and wind around the world on the globe.

What we know

Where it forms. The forecasts that show it have the centre taking shape about 100 miles northeast of San Diego, over California on Tuesday night, at about 1,004 .

How sure. 91 of 185 show the storm, and they on where it goes.1

How strong. Forecasts keep its central pressure near 1,007 through Thursday. None of them turn it into a rapidly deepening .

What’s uncertain

Whether it forms. 91 of 185 develop it; the rest do not. Storms that exist only in the forecast can change a lot from run to run.

How close it comes. For Los Angeles, most forecasts put the between 20 and 150 miles away, most likely Thursday 2 p.m.

Later on. The forecasts fan out after Wednesday. By Monday morning, Oct. 5, the is about 450 miles across.2

When it arrives

When the centre passes closest to each place, earliest to latest across the forecasts. Places are ordered by the most likely time.

Window of Most likely timeNight
is the share of forecasts that bring the centre within 100 miles. Shaded columns are night; times are in your time zone.

Rain and wind this week in San Diego, Los Angeles, San Francisco and Sacramento.

DetailsStrength, sources and the fine print

How strong it gets

Central pressure over time. The line is the middle forecast; the band holds 8 in 10 of them.

(lower is stronger)

Times are shown in

Where the forecasts come from

ModelTracks
NOAA
0 of 3118Z
arrived 2 h 45 min ago
ECMWF
44 of 5112Z
arrived 5 h 20 min ago
ECMWF
32 of 5118Z
arrived 1 h 35 min ago
NOAA
15 of 3112Z
arrived 7 h ago
Environment Canada
0 of 2112Z
arrived 8 h 50 min ago

Also tracking

  1. Southern Ocean low south of New ZealandVery deep low near 921 mb now, in the Southern Hemisphere; all 185 forecasts show it
  2. Southern Ocean lowVery deep low in the Southern Hemisphere, near 936 mb now and filling; all 185 forecasts show it
  3. Southern Ocean lowVery deep low bottoming out near 953 mb Thu morning, in the Southern Hemisphere; all 185 forecasts show it
  4. Amundsen Sea lowVery deep low bottoming out near 957 mb Tue night, in the Southern Hemisphere; all 185 forecasts show it
  5. Hurricane PoloCould pass near San Diego Wed morning; 1 in 10 forecasts bring it within 100 mi
  6. See all 30 storms →

Notes

  1. Forecast tracks from the 18Z model run: GEFS (31), ECMWF ENS (51), AIFS ENS (51), AIGEFS (31), GEPS (21). A single run is one high-resolution forecast; ensemble forecasts are the same model run many times with small changes.
  2. The cone encloses where the centre is expected to be about two times in three at each hour, from the spread of the forecasts, widened by 20 percent; not yet calibrated against past storms. It shows uncertainty in the track, not the size of the storm.
  3. Shading shows the share of forecasts that bring the centre within 100 miles of a spot at any time in the next 10 days. Rain, wind and surge can reach much farther.
  4. Times are in your time zone. Arrival windows run from the earliest to the latest closest approach across forecasts that bring the centre within about 300 miles (500 km).
  5. NOAA/NCEP.
  6. Data Source: Environment and Climate Change Canada.
  7. This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF). Source: www.ecmwf.int. Licence: CC BY 4.0.
  8. Cyclone tracks computed by Stormlines from the model fields.
  9. Reading these maps: , or the illustrated guide to spaghetti models. The week’s rain, wind and temperature everywhere: the Stormlines globe.
  10. How often these forecasts turn out right: the season’s forecast check, AI vs physics.
  11. Stormlines storm ID: L-2026-0267.

Stormlines draws every storm the world’s ensemble forecasts can see: tracks from NOAA (GEFS and the AI ensemble AIGEFS), ECMWF (ENS and the AI ensemble AIFS) and Environment Canada (GEPS), updated as each model run lands. Coastlines and place names from Natural Earth; sea areas from IHO Sea Areas, version 3 (Flanders Marine Institute, marineregions.org, CC BY 4.0; modified: simplified, some islands removed, names edited).

Not an official forecast. For warnings and decisions, follow your national weather service.

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Stormlines Tracks: NOAA, ECMWF, Environment Canada

Full forecast
Through Mon 5 a.m. PDT