AROME 1.3 km vs 2.5 km – The Resolution Jump That Changes Everything Near Shore
In the world of wind forecasts, resolution is king. The difference between 2.5 km and 1.3 km sounds small. In reality, it is the difference between seeing a blurry photo and a high-definition image.
The French model AROME operates at a stunning 1.3 km resolution. This jump in precision reveals local wingfoil wind effects that 2.5 km models simply smooth over.
The "Seeing" Distance
A weather model cannot "see" anything smaller than its grid size.
- 2.5 km Grid: A small island or a narrow valley (1 km wide) does not exist. The model treats it as flat terrain.
- 1.3 km Grid: The model sees the valley. It calculates the channeling of the wind.
For the wingfoiler, this is critical. We ride in the "near-shore" zone—the first 1000 meters from the beach. This is exactly where the topography disrupts the wind.
Deep Convection and Gusts
The 1.3 km resolution allows AROME to explicitly resolve "deep convection" (thunderstorms and strong thermals) without using approximations.
Lower resolution models (like GFS or even standard ECMWF) use "parameterization." They guess what a storm might look like based on averages. AROME 1.3 km actually simulates the physics of the storm cell.
This means AROME is often the only model that correctly predicts the short, violent wind gusts of a passing squall.
The Coastal Boundary
The boundary between land and sea is sharp. The temperature can change by 10°C in just 500 meters.
AROME 1.3 km captures this sharp gradient. It accurately predicts the thermal wind front—the exact line where the sea breeze starts. A 2.5 km model often blurs this line, predicting the wind starting 2 km offshore when it is actually blowing on the beach.
Comparison on the Water
- Scenario: A steep cliff creates a wind shadow.
- 2.5 km Model: Predicts 15 knots close to the cliff (misses the shadow).
- 1.3 km Model: Predicts 5 knots in the shadow and 20 knots further out.
For a winger, this is the difference between slogging in a lull and riding powered.
Summary
If you ride in complex terrain—bays, islands, or near mountains—you need the highest resolution possible. AROME 1.3 km offers a level of detail that turns a guessing game into a precision strike. It changes everything near shore because it finally draws the map correctly.