UK coverage is live at 4 km
The Convek API now serves high-resolution soaring forecasts across England, Wales, and southern Scotland. WRF at 4 km, four runs a day, every field available as JSON.
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Every Convek post - technical deep-dives, coverage launches, field explainers, and the occasional essay.
Why run your own WRF at all?
Global weather models stop being useful for soaring long before you reach the thermal layer. Here's why Convek runs WRF at 4 km instead of serving GFS like everyone else.
Validating against soundings and XContest traces
A forecast is not useful unless it is right. We verify Convek against radiosonde soundings and XContest flight activity. Here is the validation setup and what it says about where we are weak.
Day rating is a label, not a magic number
`day_rating` is a composite label: poor, marginal, fair, good, or excellent. Under the hood it comes from an internal score, but the API returns a readable label. Here is how to interpret it without being misled.
MPI decompositions, hyperthreads, and a lost week of compute
Getting WRF to run fast on a 12-vCPU box is a solved problem if you know the answer. We did not know the answer. Here is the week of wrong turns that eventually got UK 4 km to ~33 minutes per cycle.
Spin-up: how many hours before WRF output is real
The first few hours of any WRF run are contaminated by the model adjusting to its initial conditions. Here is how much we discard and why the four-daily cadence is designed around it.
Reading a forecast sounding without overreading it
The sounding endpoint gives you the full vertical profile at any point in the domain. Here is how to read the things a sounding is good for and ignore the things it is not.
Land surface and the soil-moisture trap
Noah-MP is the right land surface scheme for soaring. But if you feed it stale soil moisture from GFS after a dry spell, it will quietly ruin your spring forecasts. Here is how we got caught and how we fixed it.
Boundary layer height vs soaring height: they are not the same
`boundary_layer_m` and `hglider_agl_m` are two different numbers in the API. They come from the same meteorology but mean different things, and mixing them up gives you the wrong briefing.
Getting cloudbase right: the LCL formulations that didn't work
We tried four different ways of computing cloudbase from raw WRF output before settling on one that matched pilot reports. Here is what failed, and why.
`hglider_agl_m`: the glider-capped thermalling ceiling
`hglider_agl_m` is the height a glider can actually work up to, capped by cloudbase and the top of the useable thermal layer. It is not the raw boundary layer height.
YSU vs MYNN-2.5: the PBL scheme bake-off
The planetary boundary layer scheme is the single biggest lever on soaring forecast quality. We tested YSU against MYNN-2.5 across a UK convective season. Here is what won and why.
Trigger temperature: the most useful number before breakfast
`thermal_trigger_temp_c` is the surface temperature that has to be reached before the first thermal of the day breaks the morning inversion. Here is how it is computed and why pilots should care.
Thompson microphysics, and the WSM6 detour we wasted a month on
We spent October on the wrong microphysics scheme. WSM6 looked cheaper, and it was, but the cloudbase output was unusable. Here is what went wrong and how Thompson fixed it.
What `wstar_ms` actually tells you
Pilots see `wstar_ms` and read it as thermal strength in metres per second. That is not what it is. Here is what the number actually represents.
Vertical levels: why the bottom 3 km gets most of the detail
WRF gives you a vertical stack of eta levels to spend however you like. For soaring, almost all of them should live in the lowest few kilometres.
Designing the UK domain: where the edges go
The first decision in any WRF setup is where the model sees air. Here is how the Convek UK domain is laid out and why the boundaries sit where they do.