| Table of Contents | ||
|---|---|---|
|
Introduction
The ECMWF operational ensemble forecasts for the western Mediterranean region exhibited high uncertainty while Hurricane Nadine was slowly moving over the eastern N.Atlantic in Sept. 2012. Interaction with an Atlantic cut-off low produced a bifurcation in the ensemble and significant spread, which controls both the track of Hurricane Nadine and the synoptic conditions downstream.
The HyMEX (Hydrological cycle in Mediterranean eXperiment) field campaign was also underway and forecast uncertainty was a major issue for planning observations during the first special observations period of the campaign.
This interesting case study examines the forecasts in the context of the interaction between Nadine and the Atlantic cut-off low in the context of ensemble forecasting. It will explore the scientific rationale for using ensemble forecasts, why they are necessary and they can be interpreted, particularly in a "real world" situation of forecasting for a observational field campaign.
In these case study exercises
In these exercises we will look at a case study of the interaction between a Hurricane and :
- study the development of Hurricane Nadine and the interaction with the Atlantic cut-off low
...
- using the ECMWF analyses.
- study the performance of the ECMWF high resolution (HRES) deterministic forecast of the time.
- use the operational ensemble forecast to look at the forecast spread and understand the uncertainty downstream of the interaction.
- compare a reforecast using the current (May/2016) ECMWF operational ensemble with the 2012 ensemble forecasts.
- use principal component analysis (PCA)
...
- with clustering techniques (see Pantillon et al) to characterize the behaviour of the
...
- ensembles.
- see how forecast products were used during
...
- the HyMEX field campaign.
| Panel | ||
|---|---|---|
| ||
Pantillon, F., Chaboureau, J.-P. and Richard, E. (2015), 'Vortex-vortex interaction between Hurrican Nadine and an Atlantic cutoff dropping the predictability over the Mediterranean, http://onlinelibrary.wiley.com/doi/10.1002/qj.2635/abstract |
| Note | ||
|---|---|---|
| ||
In practise many cases are aggregated in order to evaluate the forecast behaviour of the ensemble. However, it is always useful to complement such assessments with case studies of individual events, like the one in this exercise, to get a more complete picture of IFS performance and identify weaker aspects that need further exploration. |
Recap
ECMWF operational forecasts consist of:
...
Obtaining the exercises
The exercises described below are available as a set of Metview macros with the accompanying data. This is available as a downloadable tarfile for use with Metview (if installed). It is also available as part of the OpenIFS/Metview virtual machine, which can be run on different operating systems.
For more details of the OpenIFS virtual machine and how to get the workshop files, please contact: openifs-support@ecmwf.int
...
.
Saving images and printing
...
If using the metview/openifs virtual machine with these exercises the recommended minimum memory is 4Gb. These exercises use a relatively large domain with high resolution data. Some of the plotting options can therefore require significant amounts of memory. If the virtual machine freezes when running metview, please try increasing the memory assigned to the VM.
Outline of the exercises
TO BE DONE (flowchart as last year?
...
Exercise 1. The ECMWF analysis
...
Recap
ECMWF operational forecasts consist of:
- HRES : T1279 (16km grid) highest resolution 10 day deterministic forecast
- ENS : T639 (34km grid) resolution ensemble forecast (50 members) is run for days 1-10 of the forecast, T319 (70km) is run for days 11-15.
| Info | ||
|---|---|---|
| ||
|
...