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Exercise 2: Operational ECMWF HRES forecast

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HRES performance

Exercise 1 looked at the synoptic development up to the 20-Sept-2012. This exercise looks at the ECMWF HRES forecast from this date and how the IFS model developed the interaction between Hurricane Nadine and the cut-off low.

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Before looking at the ensemble forecasts, first understand the performance behaviour of the operational HRES forecast of the time.

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Data is provided for a single 5 10 day forecast starting from 20th Sept 2012, as used in the paper by Pantillon et al. referred to at the start of this tutorial.

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Data is provided at the same resolution as the operational model, in order to give the best representation of the Hurricane and cut-off low iterations. This may mean that some plotting will be slow.

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The parameters available in the analyses are also available in the forecast data.

Available plot types

Task 1: Synoptic development (day 0-5)

From 20th to 25th September, Nadine had lost hurricane intensity and was slowly moving over the North Atlantic. A short-wave trough separated into a cutoff and approached from the north. Nadine interacted with a cold front associated with the cutoff on 21st September.

MSLP and geopotential height

Study the forecast scenario to day+5, focus on:

1. the evolution of Nadine,
2. the fate of the cutoff low,
3. the precipitation over France.

You can use the hres_1x1.mv and hres_2x2.mv icons in the same way as Exercise 1 when looking at the analyses.

Although the macros will animate the data for the whole forecast, for this task concentrate on the forecast for the first 5 days.

For example, to plot geopotential at 500hPa and MSLP using the hres_1x1.mv macro, right click, select Edit and putFirst plot the geopotential at 500hPa and MSLP using the hres_1x1.mv macro script to see the large scale circulation and track the development of the systems:

plot1=["z500.s","mslp"]

Drag To add the forecast track of Hurricane Nadine drag and drop the mv_track.mv icon onto the map to add the forecast track of Hurricane Nadineany map.

Temperature and mid-troposphere patterns

Next use the hres_2x2.mv macro to plot additional fields looking at different aspects of the forecasts. Right click and select 'Edit' and change the plot list to:

plot1=["t2","mslp"]
plot2=["mslp","wind10"]
plot3=["t500","z500"]
plot4=["t850","z850"]

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Precipitation over France

Choose a hres macro and plot the total precipitation (parameter: tp), near surface wind field (parameter: wind10), relative humidity (parameter: r).

Other suggested isobaric maps

Using either the hres_1x1.mv or hres_2x2.mv macro plot some of these other maps to study the synoptic development.

Task 2: Vertical structure and forecast evolution to day 10

This task examines vertical PV cross-sections of Nadine and the cutoff at different forecast times to characterize the diabatic warm core PV tower of Nadine compared to the upper level PV cold core of the cutoff.

Right-click on the icon 'hres

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Using either the hres_1x1.mv or hres_2x2.mv macro plot some of these other maps to study the synoptic development. Note for example that there should not be a strong horizontal temperature gradient around Nadine (why?) and the winds should be stronger for Nadine than the cutoff.

Vertical structure

This part of the task is to look at cross-sections through Hurricane Nadine and the cut-off low.

Right-click on the icon 'hres_xs.mv' icon, select 'Edit' and push the play button.

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This means the 'steps' value in the macros is only valid for the times:  [2012-09-20 00:00], [2012-09-21 00:00], [2012-09-22 00:00], [2012-09-23 00:00], [2012-09-24 00:00], [2012-09-25 00:00]

etc.

To change To change the date/time of the plot, edit the macro and change the line:

steps=[2012-09-22 00:00]

Changing

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cross-section location

#Cross section line [ South, West, North, East ]
line = [30,-29,45,-15]

The cross-section location (red line) can be changed in this macro by defining the end points of the line as shown above.

If the forecast time is changed, the storm centres will move and the cross-section line will need to be repositioned to follow specific features. This is not computed automatically, but must be changed by altering the coordinates above.

Suggestions for other vertical cross-sections

A reduced number of fields is available for cross-sections compared to the isobaric maps: temperature (t), potential temperature (pt), relative humidity (r), potential vorticity (pv), vertical velocity (w), wind-speed (speed; sqrt(u*u+v*v)) and wind vectors (wind3).

Choose from the following (note the cross-section macro hres_xs.mv uses slightly different names for the parameters).

A reduced number of fields is available for cross-sections compared to the isobaric maps: temperature (t), potential temperature (pt), relative humidity (r), potential vorticity (pv), vertical velocity (w), wind-speed (speed; sqrt(u*u+v*v)) and wind vectors (wind3).

Choose from the following (note the cross-section macro hres_xs.mv uses slightly different names for the parameters).

Changing cross-section location

#Cross section line [ South, West, North, East ]
line = [30,-29,45,-15]

The cross-section location (red line) can be changed in this macro by defining the end points of the line as shown above.

Remember that if the forecast time is changed, the storm centres will move and the cross-section line will need to be repositioned to follow specific features. This is not computed automatically, but must be changed by altering the coordinates above.

For help on how to save images, see the beginning of this tutorial.

Task 2: Precipitation over France

Choose a hres macro to use, plot the total precipitation (parameter: tp), near surface wind field (parameter: wind10), relative humidity (parameter: r) (and any other parameters of interest).

The macros hres_1x1.mv, hres_2x2.mv and hres_xs.mv can be used to plot and animate fields or overlays of fields from the HRES forecast.

Exercise 3 : Operational ensemble forecasts

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Make sure clustersId="off" for this task. Clustering will be used later.

Precipitation over France

Use stamp.mv and plot total precipitation ('tp') over France (mapType=2) for 00Z 24-09-2012.

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