·6 min read
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.
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Optimisation
CategoryDeep-dives into tuning WRF and RASP for soaring - physics, resolution, and validation.
·7 min read
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.
·7 min read
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.
·6 min read
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.
·7 min read
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.
·7 min read
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.
·7 min read
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.
·7 min read
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.
·6 min read
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.
·6 min read
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.