# Real GRIB inspection — evidence (2026-09-24)

File: `data/Tx_05-01-2022.grib` (from user `test.py`, ECDS `s2s-reforecasts`,
`cdsapi.Client(url="https://ecds.ecmwf.int/api")`). 294 KB, **184 messages**.

## Working request (authoritative; from test.py)
`origin=ecmwf`, model version `year=2023,month=01,day=05,time=00:00`, hindcast
`hyear=2022,hmonth=01,hday=05`, `level_type=single_level`,
`variable=maximum_2_m_temperature_in_the_last_6_hours`,
`forecast_type=control_forecast`, `leadtime_hour=[6,12,…,1104]` (6-hourly),
`data_format=grib`, `area=[30,80,0,130]` (N,W,S,E). NO `grid` key → native 1.5°.

## grib_ls (representative)
```
edition centre date     dataType gridType   typeOfLevel       level stepRange shortName
2       ecmf   20230105 cf       regular_ll heightAboveGround 2     0-6       mx2t6
2       ecmf   20230105 cf       regular_ll heightAboveGround 2     6-12      mx2t6
```

## grib_get (message 1)
```
shortName=mx2t6  name="Maximum temperature at 2 metres in the last 6 hours"
paramId=121  units=K  gridType=regular_ll
Ni=33  Nj=21  latFirst=30  latLast=0  lonFirst=81  lonLast=129
iDir=1.5  jDir=1.5  scanningMode=0  jScansPositively=0
dataDate=20220105 (=mars.hdate, init)  dataTime=0  mars.date=20230105 (model version)
stepUnits=hours  stepRange=0-6  startStep=0  endStep=6  stepType=max
typeOfLevel=heightAboveGround  level=2
marsClass=s2  marsStream=enfo  marsType=cf
```

## Valid-time / step progression (verified)
```
count=1   step 0-6      validity 2022-01-05 06:00
count=2   step 6-12     validity 2022-01-05 12:00
count=4   step 18-24    validity 2022-01-06 00:00
count=184 step 1098-1104 validity 2022-02-20 00:00
```
=> valid_time = init(dataDate) + endStep; 184 six-hour windows = 46 days × 4/day.

## cdo -f nc copy output (D6 path, confirmed)
dims: time=184 (`hours since 2022-1-5 00:00:00`), lon=33, lat=21, height=1;
var `mx2t6(time,height,lat,lon)` units K, standard_name air_temperature; CF-1.6.