Event probability products provide the probabilities of the occurrence of weather events at each grid point. The probabilities are calculated on the basis that each ensemble member is equally likely. Available parameters are listed in the Table 5.6. Temperature anomaly is defined as the deviation from the monthly climatology values linearly interpolated to the relevant day (applied at each grid point).

Table 5.6 (ECMWF Local Code Table 2, parameter table, Version Number 131)

FIELD CODE	MARS ABBREV.	FIELD NAME	UNITS	NO. OF BITS/VAL.
20	TALM2K	Temperature anomaly of at most -2 K	%	8
21	TAG2K	Temperature anomaly of at least 2 K	%	8
22	TALM8K	Temperature anomaly of at most -8 K	%	8
23	TALM4K	Temperature anomaly of at most -4 K	%	8
24	TAG4K	Temperature anomaly of at least 4 K	%	8
25	TAG8K	Temperature anomaly of at least 8 K	%	8
60	TPG1	Total precipitation of at least 1 mm	%	8
61	TPG5	Total precipitation of at least 5 mm	%	8
62	TPG10	Total precipitation of at least 10 mm	%	8
63	TPG20	Total precipitation of at least 20 mm	%	8
64	TPL01	Total precipitation less than 0.1 mm	%	8
65	TPRL1	Total precipitation rate less than 1 mm per day	%	8
66	TPRG3	Total precipitation rate of at least 3 mm per day	%	8
67	TPRG5	Total precipitation rate of at least 5 mm per day	%	8
68	10SPG10	10 Metre wind speed of at least 10 metre per second	%	8
69	10SPG15	10 Metre wind speed of at least 15 metre per second	%	8
70	10FGG15	10 Metre wind gust of at least 15 metre per second	%	8
71	10FGG20	10 Metre wind gust of at least 20 metre per second	%	8
72	10FGG25	10 Metre wind gust of at least 25 metre per second	%	8
73	2TL273	2 metre temperature less than 273.15 K	%	8

Two sets of probabilities are calculated, occurrence of instantaneous weather events and occurrence of events averaged or accumulated in time.

I) Occurrence of instantaneous weather events

TEMPERATURE ANOMALY EVENTS (at level 850 hPa)

Cold anomaly of at least -8K
Cold anomaly of at least -4K
Warm anomaly of at least 4K
Warm anomaly of at least 8K

These temperature anomaly products are available at 12 hour intervals from T+12 to T+360 inclusive.

WIND SPEED EVENTS (at level 10m)

At least 10m/s
At least 15m/s

Wind speed parameters are available 12 hourly from forecast time step T+12 to T+360 inclusive.

2 METER TEMPERATURE PROBABILITY

The probability that 2 metre temperature is less then 273.15 K.

2 meter temperature probability products are available at 12 hour intervals from T+12 to T+360 hours inclusive and for forecast step ranges 120-168, 168-240, 120-240 and 240-360 hours.

II) Occurrence of weather events accumulated over 24 hours

PRECIPITATION EVENTS

At least 1 mm in 24 hours
At least 5mm in 24 hours
At least 10mm in 24 hours
At least 20 mm in 24 hours

Precipitation event products are available for the following time steps ranges 24,12-36,24-48,36-60,48-72,60-84,72-96,84-108,96-120,108-132,120-144,132-156,144-168,156-180,168-192,180-204,192-216,204-228,216-240,228-252,240-264,252-276,264-288,276-300,288-312,300-324,312-336,324-348 and 336-360 hours.

WIND GUST AT 10 METERS PROBABILITY

Max wind gust exceeding 15 m/s
Max wind gust exceeding 20 m/s
Max wind gust exceeding 25 m/s

Wind gust products are available for the following range of time steps 24,12-36,24-48,36-60,48-72,60-84,72-96,84-108,96-120,108-132,120-144,132-156,144-168,156-180,168-192,180-204,192-216,204-228,216-240,120-168,168-240,120-240,228-252,240-264,252-276,264-288,276-300,288-312,300-324,312-336,324-348,336-360,240-360.

III) Occurrence of weather events averaged or accumulated in time

TEMPERATURE ANOMALY EVENTS (at level 850hPa)

average temperature more than 2 degrees K below climate
average temperature more than 2 degrees K above climate

These temperature anomaly products are available for time step ranges 120-168, 168-240, 120-240 and 240-360 hours.

MEAN PRECIPITATION RATE EVENTS

no rain (defined as less than 0.1mm over period)
mean precipitation rate less than 1mm/day
mean precipitation rate greater than 3mm/day
mean precipitation rate greater than 5mm/day

Mean precipitation rate event products are available for time step ranges 120-168, 168-240, 120-240 and 240-360 hours.

HORIZONTAL RESOLUTION:

- 0.25 x 0.25 degrees latitude-longitude grid, or multiples thereof (leg 1),

- 0.5 x 0.5 degrees latitude-longitude grid, or multiples thereof (leg 2),

- the Gaussian grid appropriate to the forecast model in use. The following Gaussian grid numbers are supported: 320, 200, 160, 128, 80, 48 and 32 (320 and 200 only for VarEPS leg 1 data).

- any sub-area

NOTE: The required precision for the threshold value is achieved by scaling the units, in which the meteorological parameter itself is reported, by an appropriate power of 10 (which may be positive, negative or 0).

For example: Total precipitation, is reported in units of metres. With

D = 4 and Lower threshold = 1, the value of the lower threshold is

1 * (1 metre / 10**4) or 0.1 mm;

Data values are percentage probabilities of the indicated meteorological parameter being above the lower threshold or being below the upper threshold or lying between the upper and lower thresholds.

Event Probability requirements

The following command language parameters are specific for the control and perturbed forecast requirements. Other DIS parameters are listed under the general Monthly Forecast requirements above.

TYPE

EVENT PROBABILITY

[EP]

DOMAIN

GLOBAL

[G]

NUMBER

OFF

PARAM

2 METRE TEMPERATURE LESS THAN 273.15 K

10 METRE WIND GUST OF AT LEAST 15 METRE PER SECOND

10 METRE WIND GUST OF AT LEAST 20 METRE PER SECOND

10 METRE WIND GUST OF AT LEAST 25 METRE PER SECOND

10 METRE WIND SPEED OF AT LEAST 10 METRE PER SECOND

10 METRE WIND SPEED OF AT LEAST 15 METRE PER SECOND

TEMPERATURE ANOMALY OF AT MOST -2 K

TEMPERATURE ANOMALY OF AT LEAST 2 K

TEMPERATURE ANOMALY OF AT MOST -8 K

TEMPERATURE ANOMALY OF AT MOST -4 K

[2TL273]

[10FGG15]

[10FGG20]

[10FGG25]

[10SPG10]

[10SPG15]

[TALM2K]

[TAG2K]

[TALM8K]

[TALM4K]

TEMPERATURE ANOMALY OF AT LEAST 4 K

TEMPERATURE ANOMALY OF AT LEAST 8 K

TOTAL PRECIPITATION OF AT LEAST 1 MM

TOTAL PRECIPITATION OF AT LEAST 5 MM

TOTAL PRECIPITATION OF AT LEAST 10 MM

TOTAL PRECIPITATION OF AT LEAST 20 MM

TOTAL PRECIPITATION LESS THAN 0.1 MM

TOTAL PRECIPITATION RATE LESS THAN 1 MM PER DAY

TOTAL PRECIPITATION RATE OF AT LEAST 3 MM PER DAY

TOTAL PRECIPITATION RATE OF AT LEAST 5 MM PER DAY

[TAG4K]

[TAG8K]

[TPG1]

[TPG5]

[TPG10]

[TPG20]

[TPL01]

[TPRL1]

[TPRG3]

[TPRG5]

LEVTYPE

SURFACE

PRESSURE LEVEL

[SFC]

[PL]

PL for PARAM=TALM2K/TAG2K/

TALM8K/TALM4K/TAG4K/

TAG8K only)

LEVELIST

OFF

850

(PARAM=TALM2K/TAG2K/

TALM8K/TALM4K/TAG4K/

TAG8K only)

GRID

*/*

AUTOMATIC [AUTO]

If the form a/b is used, a latitude-longitude grid is defined, where:

a= grid resolution (deg.) along a latitude line (i.e. East/West)

b= grid resolution (deg.) along a longitude line (i.e. North/South)

0.5/0.5 or multiples thereof;

If a single positive integer is coded, it is interpreted as Gaussian grid number for grids defined as GAUSSIAN=REDUCED or REGULAR. The following Gaussian grid numbers are supported: 200, 160, 128, 80, 48 and 32 (200 and 160 only for VarEPS leg 1 data);

AUTOMATIC - values for the parameter GRID will be defined automatically based on STREAM/DOMAIN as well as RESOL/ GAUSSIAN parameter values;

STEP

* (hours)

As described for each individual product above.

NB ALL is not permitted.

GRIB section 1 definition for Probability products

By convention, ECMWF always uses octet 41 to define which set of local definitions follow. The set of local definitions for EPS Probability fields:

Table 5.7 GRIB section 1 definition for Probability products

Octet

Ksec1

element

Contents

ECMWF local GRIB use definition identifier.

5 = Event probability data.

44-45

46-49

Class:

1 = Operations

Type:

30 = Event probability

Stream:

1035 = Ensemble forecasts

Version number or experiment identifier.

(4 ASCII characters, right justified)

Set to 0 (Event probability number);

Set to 0 (Total number of probabilities);

54-55

56-57

Threshold units decimal scale factor. + or - power of

10 (or zero). Most significant bit = 1 for negative

values.

Threshold indicator:

1 = Only lower threshold is present.

2 = Only upper threshold is present.

3 = Both upper and lower thresholds are present

Lower threshold value.

Upper threshold value.

18-01-2011