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Storm · Forecasts split · Forecast to formNorth Pacific

A new low might form southeast of Petropavlovsk-Kamchatsky on Friday evening

North Pacific — Forecast to form Fri evening, about 90 km SE of Petropavlovsk-Kamchatsky; 3 in 10 forecasts show it.

Updated Tues., Sept. 29, 12:47 a.m. UTC · 62 forecast tracks from NOAA, ECMWF and Environment Canada: medium

North Pacific — Forecast to form Fri evening, about 90 km SE of Petropavlovsk-Kamchatsky; 3 in 10 forecasts show it.

Quick answers

As of the Mon 28 Sep 12Z–18Z model runs · updated Tues., Sept. 29, 12:47 a.m. UTC

Where will the Sea of Japan low form?
Forecasts that develop it have the centre forming about 90 kilometres southeast of Petropavlovsk-Kamchatsky on Friday evening. The forecasts split: 7 in 10 move more slowly, while 3 in 10 move faster.
How sure is the forecast?
Path certainty: medium. 62 of 185 show the storm, and they closely on its path. Little has changed since the previous run.
Do the AI and physics models agree?
Broadly, with some differences. 6 in 10 AI- (AIFS ENS, AIGEFS) move more slowly, against 7 in 10 physics-ensemble forecasts (GEFS, ECMWF ENS, GEPS). By Sunday evening, Oct. 4 the AI ensembles’ middle track is about 210 kilometres east of the physics ensembles’. At its deepest, the AI ensembles take it to about 979 and the physics ensembles to about 976 mb.
Will the Sea of Japan low become a bomb cyclone?
11% of forecasts (1 in 10) 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 90 kilometres southeast of Petropavlovsk-Kamchatsky on Friday evening, at about 982 .

How sure. 62 of 185 show the storm, and they closely on its path. Little has changed since the previous run.1

How strong. It is still strengthening: forecasts deepen it to about 976 by Saturday afternoon. One in 10 forecasts make it a , deepening about 24 millibars or more in a day.

What’s uncertain

Whether it forms. 62 of 185 develop it; the rest do not. Storms that exist only in the forecast can change a lot from run to run.

Which way it turns. Seven in 10 forecasts move more slowly; the other three in 10 move faster. By Monday evening, Oct. 5 the two paths are about 650 kilometres apart.

Later on. The forecasts fan out after Saturday. By Tuesday afternoon, Oct. 6, the is about 1,400 kilometres 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 160 kilometres. Shaded columns are night; times are in your time zone.

Rain and wind this week in Petropavlovsk-Kamchatsky and Unalaska.

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

ModelTracksStatus
NOAA
19 of 3118Z
arrived 1 h 47 min ago
Latest run
ECMWF
14 of 5112Z
arrived 4 h 23 min ago
Latest run
ECMWF
7 of 5118Z
arrived 37 min ago
Latest run
NOAA
12 of 3112Z
arrived 6 h 5 min ago
Latest run
Environment Canada
10 of 2112Z
arrived 7 h 53 min ago
Latest run

Also tracking

  1. Hurricane PoloCould pass near San Diego Wed morning; 2 in 10 forecasts bring it within 160 km
  2. Southern Ocean lowVery deep low in the Southern Hemisphere, near 936 mb now and filling; all 185 forecasts show it
  3. Amundsen Sea lowVery deep low bottoming out near 956 mb Tue night, in the Southern Hemisphere; all 185 forecasts show it
  4. Southern Ocean lowVery deep low bottoming out near 953 mb Thu morning, in the Southern Hemisphere; nearly all forecasts show it
  5. Southern Ocean low south of New ZealandVery deep low near 922 mb now, in the Southern Hemisphere; 9 in 10 forecasts show it
  6. See all 27 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 160 kilometres 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-2026-0216.

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 Thu 6 a.m. UTC