Barometric Pressure Forecast

Surface pressure charts, high and low pressure system tracking, and isobar patterns for maritime route planning. ECMWF and GFS models — 10-day forecast.

Forecast Model

ECMWF + GFS

Forecast Range

10 days

Update Frequency

6-hourly

Normal MSL Pressure

1013.25 hPa

Pressure Range Guide

> 1030 hPa

High pressure / Anticyclone

Fine, settled, light winds — Sea state: Calm to slight

1020–1030 hPa

Moderate high pressure

Generally fair, variable winds — Sea state: Slight to moderate

1010–1020 hPa

Near normal pressure

Variable — monitor trend — Sea state: Moderate

1000–1010 hPa

Frontal system / Low pressure

Unsettled, increasing winds, rain — Sea state: Moderate to rough

990–1000 hPa

Deep low / Developing storm

Strong winds, squally, heavy rain — Sea state: Rough to very rough

< 990 hPa

Severe storm / Tropical cyclone

Gale to storm force winds — Sea state: Very rough to phenomenal

Pressure Tendency Interpretation

Rising quickly (> 3 hPa/3hr)

High pressure building, weather improving — squalls possible as frontal system clears

Rising slowly (1–3 hPa/3hr)

Gradual improvement, settling weather — typical recovery after frontal passage

Steady (< 1 hPa/3hr)

Stable pressure — weather likely to persist; no imminent frontal activity

Falling slowly (1–3 hPa/3hr)

Deteriorating conditions ahead — approaching frontal system, increase in wind likely

Falling quickly (> 3 hPa/3hr)

Rapid deepening low — severe weather imminent; gale warning conditions likely

Falling very rapidly (> 6 hPa/3hr)

Explosive cyclogenesis / bomb low — storm conditions, take avoiding action

Permanent High Pressure Systems

Azores High

Year-round

N Atlantic (30–40°N, 20–30°W)

Blocks Atlantic depressions — affects routing of Atlantic westbound vessels; trade wind generation

Bermuda-Azores High

Summer peak

W Atlantic (25–35°N)

Hurricane steering mechanism — clockwise circulation drives tropical cyclone tracks

South Atlantic High

Year-round

S Atlantic (25–35°S)

Drives SE trade winds; important for Cape Horn and South Atlantic routing

Pacific High

Year-round

E Pacific (25–35°N)

Drives NE trade winds across Pacific; clockwise circulation affects trans-Pacific routes

Mascarene High

Year-round

S Indian Ocean (25–35°S)

Drives SE trades in Indian Ocean — controls monsoon onset timing