Proposed Predictability, Dynamics & Ensemble Forecasting Expert Team

Richard Swinbank, with Heini Wernli, Masayuki Kyouda and Istvan

Szunyogh,and thanks to other WG members

Joint THORPEX-ICSC & WWRP-JSC meetings, Geneva, July 2013

Contents

Current scope of GIFS-TIGGE and PDP working groups

Proposed new expert team / working group

Scientific linkages between dynamical processes, predictability and ensemble forecasting.

The group’s role within new WWRP structure

TIGGE – Research focus

The TIGGE project (& GIFS-TIGGE working group) was originally focused on the technical work enabling the establishment of the TIGGE archive dataset. The main scientific aspects of THORPEX were covered by Predictability & Dynamical Processes WG, and also Data Assimilation & Observing Systems WG(s).Following the successful establishment of the TIGGE dataset, the focus of the GIFS-TIGGE working group has shifted towards research on ensemble forecasting. Particular topics of interest include:

a posteriori calibration of ensemble forecasts; combination of ensembles produced by multiple models; research on and development of probabilistic forecast products.

More recently, we have broadened our range of interest to cover improvement of EPSs, including:

representing uncertainties in initial conditions stochastic physics & other techniques to account for model error

PDP group - scope

Since its inception, the PDP working group has covered many aspects of predictability and dynamical processes,

… including the theoretical basis of ensemble forecasting.

The group brings together experts from both academia and operational NWP centres, to accelerate the transfer of cutting-edge science to operational weather forecasting.

It encourages the research community to carry out studies to improve the understanding of the relationship between particular dynamical processes and weather forecast accuracy.

Looking forward -A proposed new working group

The logical evolution of the THORPEX working groups would be the creation of a Predictability Dynamics & Ensemble Forecasting working group, combining elements of the current GIFS-TIGGE and PDP groups.

This new group would provide a centre of scientific expertise on dynamics, predictability and ensemble forecasting that is currently lacking in the core WWRP programme.

Triangular relationship

There are strong links between the three elements of the proposed group

Typhoon Malakas case study

The connections between predictability, dynamics and ensemble forecasting is illustrated by “Predictability of the Tropical Cyclone–Extratropical Flow Interaction Associated with Typhoon Malakas (2010) and Resulting High-Impact Weather Downstream” by Archambault et al (DACA-13)

Typhoon outflow

ET transition at0 UTC 25th Sept

GFS ensemble forecast of Rossby wave train

Ensemble membersEnsemble meanAnalysis

0000 UTC 20 Sep initialization

340-K isentrope on the dynamic tropopause (2-PVU surface)

Verifying 0000 UTC 25 Sep

120-h forecast T+0 h

With thanks to Heather Archambault

GFS ensemble forecast of Rossby wave train

Ensemble membersEnsemble meanAnalysis

0000 UTC 20 Sep initialization

340-K isentrope on the dynamic tropopause (2-PVU surface)

Verifying 0000 UTC 27 Sep

168-h forecast T+48 h

With thanks to Heather Archambault

GFS ensemble forecast of TC–extratropical flow interaction (T+0 h)

Ensemble membersEnsemble meanAnalysis

MSLP of 945 hPa

0000 UTC 20 Sep initialization Verifying 0000 UTC 25 Sep340-K isentrope on the dynamic tropopause (2-PVU surface)

With thanks to Heather Archambault

GFS ensemble forecast of TC–extratropical flow interaction (T+0 h)

Ensemble membersEnsemble meanAnalysis

1000-hPa MSLP contoursTC is too weak and too far

east in forecasts

0000 UTC 20 Sep initialization Verifying 0000 UTC 25 Sep340-K isentrope on the dynamic tropopause (2-PVU surface)

MSLP of 945 hPa

With thanks to Heather Archambault

Ensemble membersEnsemble meanAnalysis

0000 UTC 20 Sep initialization

340-K isentrope on the dynamic tropopause (2-PVU surface)

Verifying 0000 UTC 25 Sep

ECMWF ensemble forecast of Rossby wave train

120-h forecast T+0 h

With thanks to Heather Archambault

Ensemble membersEnsemble meanAnalysis

0000 UTC 20 Sep initialization

340-K isentrope on the dynamic tropopause (2-PVU surface)

Verifying 0000 UTC 27 Sep

ECMWF ensemble forecast of Rossby wave train

168-h forecast T+48 h

With thanks to Heather Archambault

15

WWRP structure and links to WCRP

15

Scope of new Projectsfocused on key “hot spots”

Time scale

S2S

HIW

PPP

WWRP domain

…while expert teams shouldcover the entire domain

Role

Foster scientific research on dynamics, predictability and ensemble forecasting

Support for WWRP projects PPP, S2S, HIW, FDPs, RDPs

Bridge between academic & operational communities Steering development of ensemble prediction

databases (TIGGE and TIGGE-LAM) to support scientific research

Promote use of EPS datasets by the research community

Scientific Scope

Centre of expertise on dynamical processes, predictability and ensemble forecasting.

Understanding & improving probabilistic predictive skill, and its links with dynamical phenomena

Scientific issues include Growth & evolution of errors Stochastic representation of unresolved processes

Covering short- to medium-range forecast timescales (potentially longer)

Relationship with other teams / groups

There are clear linkages with WGNE and other WWRP expert teams. Numerical modelling, Ensembles, Data assimilation, Stochastic parameterization and Evaluation

…are all closely linked on both weather and climate timescales.

Too big for a single expert team or working group – we need a set of more specialised teams…

providing expert support to WWRP projects (S2S, PPP, HIW, RDPs & FDPs)

Other issues

Current GIFS-TIGGE rolesDevelopment of severe weather products

Would fit well into scope of proposed HIW project.Technical management of data archives:

On-going maintenance should be continued through liaison between archive centres & data providers via email;

Management should be overseen by PDEF team. Representative of archive centre on ET.

Current PDP rolesTreatment of systematic model errors

Would be subsumed in WGNE.

Next Steps

Provided that this meeting agrees that the proposed expert team (/working group) is the best way forward…

Approval will be required by CAS (Nov 2013) & WMO-EC (Spring 2014).

Transition arrangements Arrange joint PDP/GIFS-TIGGE meeting in early 2014, to

agree detailed scope & responsibilities of the expert team. Work towards merger of GIFS-TIGGE and PDP groups at end

of 2014 New members of both groups chosen for role in new team.