Oscar Martínez-Alvarado

NAWDEX-UK Forecast Products

The data to produce these plots is supplied by the European Centre for Medium-Range Forecasts (ECMWF). The ECMWF Data Server is used to download and process the data.

Notice that there is delay of 10 hours between the forecasts' nominal base timesand these plots becoming available.

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List of parameters

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Parameter	Description
PV on the 320-K isentropic surface
320-K PV	Shading: Control member 320-K PV, in PVU; Black line: Control member 320-K 2-PVU; Grey lines: Ensemble members 320-K 2-PVU
320-K Troposphere probability	Shading: Ensemble-derived probability of being on tropospheric air at 320 K, i.e. Ntropos / N, where Ntropos = number of ensemble members satisfying the condition PV<2 PVU and N = total number of ensemble members (for ECMWF, N = 50); Black line: Control member 320-K 2-PVU; Purple line: 320-K 2-PVU in ensemble member with maximum RMS error with respect to the control member (Notice that purple contours are not part of a single model-generated orbit)
Atmospheric blocking
The assessment of atmospheric blocking is done using the method by Scherrer et al. (2006, doi:10.1002/joc.1250) without the five-day persistence condition, i.e. if the following two conditions are met, the grid point at ϕ0 is said to be blocked GHGS = [Z(ϕ0) - Z(ϕS)]/[ϕ0 - ϕS] > 0 and GHGN = [Z(ϕ0) - Z(ϕN)]/[ϕ0 - ϕN] < -10 m deg-1, where Z is 500-hPa geopotential height, ϕS = ϕ0 - 15o and ϕN = ϕ0 + 15o. The test is performed on every grid point within the band -180o < λ ≤ +180o in longitude and 35o < ϕ0 < 75 in latitude. See also Schiemann et al. (2016, in preparation).
Blocking probability	Shading: Atmospheric blocking ensemble-derived probability, i.e. Nblocked / N, where Nblocked = number of ensemble members satisfying blocking conditions and N = total number of ensemble members (for ECMWF, N = 50)
GHGS+320-K 2-PVU	Shading: Southern geopotential height gradient (GHGS) over instantaneously blocked regions in control member; Black line: Control member 320-K 2-PVU
GHGS+330-K 2-PVU	Shading: GHGS over instantaneously blocked regions in control member; Black line: Control member 330-K 2-PVU
GHGS+350-K 2-PVU	Shading: GHGS over instantaneously blocked regions in control member; Black line: Control member 350-K 2-PVU
Pressure on isentropic surfaces
315-K p	Shading: 315-K pressure, in hPa; Black line: Control member 315-K 2-PVU
330-K p	Shading: 330-K pressure, in hPa; Black line: Control member 330-K 2-PVU
350-K p	Shading: 350-K pressure, in hPa; Black line: Control member 350-K 2-PVU
Divergence on isobaric surfaces
500-hPa divergence	Shading: 500-hPa divergence, in 10-4 s-1; Thin line: Control member 500-hPa geopotential height, in dm Bold line: Control member 500-hPa 2-PVU
300-hPa divergence	Shading: 300-hPa divergence, in 10-4 s-1; Thin line: Control member 300-hPa geopotential height, in dm Bold line: Control member 300-hPa 2-PVU
200-hPa divergence	Shading: 200-hPa divergence, in 10-4 s-1; Thin line: Control member 200-hPa geopotential height, in dm Bold line: Control member 200-hPa 2-PVU
Relative vorticity on isobaric surfaces
500-hPa vorticity	Shading: 500-hPa relative vorticity, in 10-4 s-1; Thin line: Control member 500-hPa geopotential height, in dm Bold line: Control member 500-hPa 2-PVU
300-hPa vorticity	Shading: 300-hPa relative vorticity, in 10-4 s-1; Thin line: Control member 300-hPa geopotential height, in dm Bold line: Control member 300-hPa 2-PVU
200-hPa vorticity	Shading: 200-hPa relative vorticity, in 10-4 s-1; Thin line: Control member 200-hPa geopotential height, in dm Bold line: Control member 200-hPa 2-PVU

Plots

Parameters Description	320-K PV 320-K Troposphere probability Blocking probability GHGS+320-K 2-PVU GHGS+330-K 2-PVU GHGS+350-K 2-PVU 315-K p 330-K p 350-K p 500-hPa divergence 300-hPa divergence 200-hPa divergence 500-hPa vorticity 300-hPa vorticity 200-hPa vorticity
ECMWF	320-K PV
Validation time
-3 h +3 h -1 d +1 d	Forecast base time control: -24 h +24 h
	T+0
	T+24
	T+48
	T+72