To contact ESTOFEX you can send an e-mail to .

What does ESTOFEX forecast?

The European Storm Forecast Experiment is an initiative of a team of European meteorologists, meteorology students and trained enthusiasts, who intend to learn how to forecast severe convective storms in Europe.

Our goals are:

to issue daily forecasts of severe convective weather in Europe, using an ingedients-based forecasting methodology

to enhance the understanding of severe convective storms in Europe, both among ourselves and others

to help establish and promote the European Severe Weather Database (ESWD) as a basis for severe weather research

to establish a method to verify the forecasts, based on ESWD and lightning data

What does ESTOFEX forecast?

ESTOFEX issues "Storm Forecasts" on a daily basis. These bulletins, that are accompanied by a map, address the threats posed by severe convective storms in Europe. The focus of the forecasts are the threats of hail, severe wind gusts and tornadoes that these storms pose. The forecasts additionally indicate where lightning or severe gusts (that need not be associated with convective storms) are expected to occur.

How to interpret the forecasts?

To communicate the magnitude of the threat of hail, severe wind gusts and tornadoes, ESTOFEX uses four threat levels. These are issued based on the expected coverage of severe weather produced by severe and extremely severe convective storms.

A severe convective storm is defined as a convective storm that is accompanied by either

hail with a diameter of at least 2.0 cm, or

wind gusts with a speed of at least 25 m/s (92 km/h or about 48.6 knots), or

a tornado.

A extremely severe convective storm is defined as a convective storm that is accompanied by either

hail with a diameter of at least 5.0 cm, or

wind gusts with a speed of at least 33 m/s (about 119 km/h or 65 knots), or

a tornado of class F2 or stronger

The threat levels are defined as follows:

(severe convective storms unlikely)

This is an area in which severe storms will probably not occur. This threat level is valid for all areas that are not included in a threat level 1, 2, or 3.

threat level

1

Threat level 1 is issued when a small number of severe convective events are forecast. Typically, level 1 will be issued when one can expect two to four large hail, severe wind or F0 - F1 tornadoes to occur per area of 500 km x 500 km. A typical situation would be that of a few isolated severe storms or a large convective system that produces only a few events meeting the 'severe' criteria.

threat level

2

Threat level 2 is issued when a large number of severe convective events are forecast and/or a small number of extremely severe convective events. Often one will have a mixture of both. A level 2 can, for example, be issued when rather widespread convective winds are expected, that however are not expected to exceed 33 m/s in many places. Another possibility would be a day on which a number of storms are forecast to bring large hail and severe winds to quite a number of places, but with hail larger than 5.0 cm and winds > 33 m/s not very likely. An area where some supercells could bring a few tornadoes of which some likely exceed the F1 category, is another typical example.

threat level

3

Threat level 3 is issued when a large number of extremely severe convective events are forecast. Level 3 is rarely issued and implies a major severe weather outbreak is expected. An example is a long-lived convective windstorm (also called derecho), that brings winds in excess of 33 m/s to quite a number of places. Examples include the derecho that struck a large part of Germany on July 10th 2002. Major tornado outbreaks also require a level 3. An example is the outbreak that occurred on June 25th 1967 across France, Belgium and the Netherlands.

The following table summarizes the above.

Apart from the threat areas, the maps show - marked by a yellow line - the areas where thunderstorms are forecast. Additionally, a light blue line marks the area where non-convective wind gusts of 25 m/s are forecast to occur.

For more information about severe storms see the research and education page.

Looking at numerical model output and observational data, such as soundings, we use an "ingredients-based" methodology:

Several physical parameters need to come together in order to produce a storm and severe weather. Low-level moisture and steep lapse rates combine into latent instability. Instability needs a trigger in order to be released and generate a storm, that by deep lifting. This can be generated by various mechanisms at different scales that also have an influence on the coverage of storms.

Once a storm forms, its development is strongly influenced by the interaction with the flow in its environment. Depending on the direction and magnitude of the winds at various altitudes - among other factors - the storm may grow into several types like multicell clusters, squall lines and supercell storms. In the forecast, we use several parameters that have been proven to have a predictive value of storm types.

When we have a good impression of the factors that influence the organisation of the storms on a particular day, we determine the likelihood of severe weather based on the characteristics of a particular storm environment, the expected storm type and coverage and translate that conceptual picture into risk categories.

Due to the lack of severe weather reports reaching us, we currently have insufficient means of verifying our forecasts. However, we do plan to verify our TSTMS line against SFLOC data (lightning) once we have the means (e.g. digitization of the forecast maps) and necessary statistical knowledge to develop a verification system. In the mean time, we judge each forecast by means of observed lightning data, storm types as seen on satellite and radar images, and your reports.

We appreciate your help! We are in great need of reports of severe weather to verify our forecasts. We cannot improve our forecasts if we don't know what severe weather has happened. So, submitting your severe weather report to the ESWD database will certainly help! Besides reports, we could use more observational data, such as real-time radar and analysis tools.

ESTOFEX is looking for persons who:

are willing to contribute regularly in discussions

have experience in forecasting and/or research of thunderstorms and severe weather

had a preferably academic education in meteorology or physics

have qualities in e.g. programming, numerical modelling or statistics to advance our goals

If you feel suited to join us, please introduce yourself by sending an email to the above address. We especially welcome applications from people from Southern Europe, Scandinavia and Eastern Europe, and from women.

Although we hope that we can eventually be funded, we will probably have to keep operating on a voluntary basis for some time to come.

This is a misunderstanding. ESTOFEX does not issue warnings. At least not in the sense that the general public is advised to take immediate action. In most countries, national meteorological institutes issue such warnings, while commercial companies may offer similar products.

The Storm Forecasts by ESTOFEX are forecasts that are valid for an entire day or a large part of a day and cover large areas. Although certain non-meteorological users may find the information useful, our primary targets are meteorologically educated people. Therefore, the forecast texts are often quite technical. Similar to the Storm Prediction Center in the U.S.A. we can provide guidance to other meteorologists. Our forecasts may be one of the data sources for a meteorologist on duty to consult. It must be noted, however, that we are an 'experiment' and therefore cannot take any responsibility with respect to the quality or availability of the products.

ACCAS	Altocumulus castellanus
ATTM	at the moment
AVA	anticyclonic vorticity advection
BENELUX	BElgium, NEtherlands and LUXembourg
BL	boundary layer
BOLAM	Bologna Limited Area Model
C	degrees Celsius
CAA	cold air advection
CAPE	convective available potential energy
CB	cumulonimbus
CCL	convective condensation level
CIN/CINH	convective inhibition
CU	cumulus
CVA	cylonic vorticity advection
DCVA	differential cyclonic vorticity advection
DD	dewpoint depression, difference between temperature and dewpoint temperature
DLS or DL shear	Deep-layer shear: 0-6 km difference vector length
E	east
EC	enhanced cumulus clouds
ECM	Global numerical model from European Centre for Medium-Range Weather Forecasts (ECMWF)
EL	equilibrium level
EML	elevated mixed layer
ERN	eastern
FCST	forecast
GEN TSTMS	general thunderstorms
GME	Global model of the Deutscher Wetterdienst (DWD)
HPA	hectopascal(s)
KNMI-HIRLAM	HIgh Resolution Local Area Model run at Dutch Royal Met. Inst. (KNMI)
KTS	knots
LCL	lifted condensation level
LEWP	line-echo wave pattern
LFC	level of free convection
LI	Lifted Index
LILAM	LIguria Local Area Model
LL	Low-level (e.g. 0-1 km layer)
LLS or LL shear	Low-level shear: 0-1 km difference vector length
LM	local model of the Deutscher Wetterdienst (DWD)
MCS	mesoscale convective system
MDT RISK	moderate risk
MLCAPE	mixed-layer CAPE
MLCAPE30	CAPE calculated using a parcel mixed over the lowest 30 hPa of the troposphere
MLCAPE50	CAPE calculated using a parcel mixed over the lowest 50 hPa of the troposphere
MLCAPE100	CAPE calculated using a parcel mixed over the lowest 100 hPa of the troposphere
MM5	Mesoscale and Microscale Modeling System Version 5, NCAR
MUCAPE	most unstable CAPE
MULI	most unstable lifted index
N	north
N/A	not available
NRN	northern
NE	northeast
NERN	northeastern
NW	northwest
NWRN	northwestern
OBS	observed/observation
PBL	planetary boundary layer
PRECIP	precipitation
PRIND	present indications are
QG	quasi-geostrophic
QPF	quantitative precipitation forecast
S	south
SAT	satellite
SBCAPE	surface-based CAPE
SE	southeast
SERN	southeastern
SFC	surface
SLGT RISK	slight risk
SRH	storm-relative helicity
SRN	southern
SW	southwest
SWRN	southwestern
SVR TSTMS	severe thunderstorms
TCU	towering cumulus (cumulus congestus)
THETA-E	equivalent potential temperature
UKMO	Global numerical model from U.K. Met. Office
UVM	upward vertical motion
W	west
WAA	warm air advection
WBZ	wet-bulb zero temperature
WRN	western
VORT MAX	vorticity maximum
Z	UTC (universal time coordinated)