# 3. METexpress Apps

This section includes a description of the unique features of each app.

## 3.1. Upper Air App

The Upper Air app is designed for plotting scalar and contingency table statistics at different pressure levels in the atmosphere.

The user interface for Upper Air follows the general description from above. Choices specific to this app are shown below.

Choices for Statistic (depending on available line types):

RMSE

Bias-corrected RMSE

MSE

Bias-corrected MSE

ME (Additive bias)

Multiplicative bias

Forecast mean

Observed mean

Forecast stdev

Observed stdev

Error stdev

Pearson Correlation

Forecast length of mean wind vector

Observed length of mean wind vector

Forecast length - observed length of mean wind vector

abs(Forecast length - observed length of mean wind vector)

Length of forecast - observed mean wind vector

abs(Length of forecast - observed mean wind vector)

Forecast direction of mean wind vector

Observed direction of mean wind vector

RMSE of forecast wind vector length

RMSE of observed wind vector length

Vector wind speed MSVE

Vector wind speed RMSVE

Forecast mean of wind vector length

Observed mean of wind vector length

Forecast mean - observed mean of wind vector length

abs(Forecast mean - observed mean of wind vector length)

Forecast stdev of wind vector length

Observed stdev of wind vector length

The Upper Air app includes functionality for these types of plots:

Time Series

Profile

Dieoff

ValidTime

Histogram

Contour

The Upper Air app includes the following plot types.

**Time Series**: The default plot type is Time Series, which has date on
the x-axis and the mean value of the selected parameter for that date on
the y-axis.

**Profile**: The Profile plot type displays pressure level on the y–axis
and the mean value of the selected parameter on the x-axis.

**Die-off**: Die-off plots show how skill (or the inverse, error)
changes with increasing lead time. Figure 3.1 shows the user
interface page after selecting the plot type of DieOff. Note that
another selector is included for DIEOFF TYPE, which has the following
possible values:

Dieoff

Dieoff for a specific UTC cycle start time

Single cycle forecast

Figure 3.2 shows a sample of a DieOff plot in METexpress. This looks more like a familiar die-off curve when plotting skill, such as anomaly correlation as plotted in Figure 3.3 using the Anomaly Correlation app, rather than error as is plotted with the Upper Air app.

The option “dieoff” for Dieoff Type uses all data at each given forecast hour within the specified date range. The option for “Dieoff for a specific UTC cycle start time” filters data to only use those at a specified cycle initialization time, such as 0 or 12. The option “Single cycle forecast” uses only the forecasts from the first cycle in the specified date range.

**ValidTime**: The ValidTime plot type (also sometimes known as diurnal
cycle plots) displays valid UTC hour on the x–axis and the mean value of
the selected parameter on the y-axis.

**Histograms**: Histograms allow users to visualize the distribution of
a given statistic over a specified time period. For example, if a user
requested a histogram of RMSE for 144-h GFS forecasts over the global
domain for a month, they would see the frequencies of specific RMSE values
produced by individual GFS runs over that month. Histograms have statistical
value bins on the x-axis, and number or frequency counts on the y-axis.

Histograms have a number of additional selectors that control their appearance:

Y-axis mode: Can be set to either “Relative frequency” or “Number”, depending on whether a user wants the frequency of a given statistic displayed as a fraction of 100, or as a raw count.

Customize bins: With this selector, the user can choose one of the following options to customize their x-axis bins:

Default bins

Set number of bins

Has sub-selector “Number of bins”

Make zero a bin bound

Choose a bin bound

Has sub-selector “Bin pivot value”

Set number of bins and make zero a bin bound

Has sub-selector “Number of bins”

Set number of bins and choose a bin bound

Has sub-selectors “Number of bins” and “Bin pivot value”

Manual bins

Has sub-selector “Bin bounds”

Manual start, number, and stride

Has sub-selectors “Number of bins”, “Bin start”, and “Bin stride”

Figure 3.4 shows the user interface for histogram plots and Figure 3.5 shows a sample plot.

**Contour**: Contour plots can be used in many ways. One can illustrate
data with respect to height, as in plots seen at
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/,
which have height on the y-axis and forecast hour (as in lead time) on
the x-axis. These VSDB stat plots can be easily replicated in METexpress
by using the contour plot type, except that the plot in METexpress will have
only one pane, not two. In addition, METexpress users are not bound to have
only pressure level / height on the y-axis or forecast lead time on the x-axis.
They can reverse the two, place valid or init UTC hour on one of the axes,
create Hovmoller diagrams, and many other combinations.

Contour plots have two additional selectors, x-axis-parameter and y-axis-parameter. With these, a user can decide which field to place on the x-axis (e.g. forecast lead time), and which to place on the y-axis (e.g. pressure level or valid UTC hour).

Figure 3.6 shows an example of an Upper Air profile plotted as a contour plot.

## 3.2. Anomaly Correlation App

The Anomaly Correlation app is designed for plotting anomaly correlations at different pressure levels in the atmosphere, and at different heights above the ground.

An example of the Anomaly Correlation app user interface is shown in Figure 3.7 This interface is similar to the one for Upper Air but has fewer selectable parameters.

In this application, the selectable values are derived from the data for these parameters:

Group

Database

Data-Source

Region

Statistic

Variable

Interp-Method

Scale

Forecast lead time

Level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

ACC

Vector ACC

Plot types available include

Time Series

Profile

DieOff

ValidTime

Histogram

Contour

All plot types function the same here as they do in MET Upper Air described above. A sample anomaly correlation plot is shown in Figure 3.8.

## 3.3. Surface App

The Surface app is designed for plotting scalar and contingency table statistics at different heights above the ground.

The user interface for the Surface app is shown in Figure 3.9.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Region

Statistic

Variable

Interp-Method

Scale

Forecast lead time

Ground level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

RMSE

Bias-corrected RMSE

MSE

Bias-corrected MSE

ME (Additive bias)

Multiplicative bias

Forecast mean

Observed mean

Forecast stdev

Observed stdev

Error stdev

Pearson Correlation

Forecast length of mean wind vector

Observed length of mean wind vector

Forecast length - observed length of mean wind vector

abs(Forecast length - observed length of mean wind vector)

Length of forecast - observed mean wind vector

abs(Length of forecast - observed mean wind vector)

Forecast direction of mean wind vector

Observed direction of mean wind vector

RMSE of forecast wind vector length

RMSE of observed wind vector length

Vector wind speed MSVE

Vector wind speed RMSVE

Forecast mean of wind vector length

Observed mean of wind vector length

Forecast mean - observed mean of wind vector length

abs(Forecast mean - observed mean of wind vector length)

Forecast stdev of wind vector length

Observed stdev of wind vector length

Plot types available include:

Time Series

DieOff

ValidTime

Histogram

Contour

Plots in the Surface app for Time Series, DieOff, ValidTime, Histogram, and Contour are the same as in Upper Air. An example of a Valid Time plot is shown in Figure 3.10.

## 3.4. Air Quality App

Similarly to the Surface app, the Air Quality app is designed for plotting scalar and contingency table statistics at different heights above the ground, but with a focus on variables related to air quality.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Region

Statistic

Variable

Threshold

Interp-Method

Scale

Forecast lead time

Ground level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

CSI

FAR

FBIAS

GSS

HSS

PODy

PODn

POFD

RMSE

Bias-corrected RMSE

MSE

Bias-corrected MSE

ME (Additive bias)

Multiplicative bias

Forecast mean

Observed mean

Forecast stdev

Observed stdev

Error stdev

Pearson Correlation

Plot types available include

Time Series

DieOff

Threshold

ValidTime

Histogram

Contour

Plots in the Air Quality app for Time Series, DieOff, ValidTime, Histogram, and Contour are the same as in Upper Air.

An additional plot type, Threshold, is available in this app. Threshold plots display threshold on the x-axis, and the mean value of the selected parameter on the y-axis.

Figure 3.11 shows an example of an Air Quality Threshold plot.

## 3.5. Ensemble App

The Ensemble app is designed for plotting scalar and contingency table statistics, as well as ensemble metrics, for multi-member ensemble model runs.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Region

Statistic

Variable

Forecast lead time

Level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

RMSE

RMSE with obs error

Spread

Spread with obs error

ME (Additive bias)

ME with obs error

CRPS

CRPSS

MAE

ACC

BS

BSS

BS reliability

BS resolution

BS uncertainty

BS lower confidence limit

BS upper confidence limit

ROC AUC

EV

FSS

Plot types available include

Time Series

DieOff

ValidTime

Histogram

Ensemble Histogram

Reliability

ROC

Performance Diagram

Plots in the Ensemble app for Time Series, DieOff, ValidTime, and Histogram are the same as in Upper Air.

Four plot types are specific to this app: Ensemble Histogram, Reliability, ROC, and Performance Diagram.

Ensemble Histograms are controlled by the Histogram type selector that appears at the bottom of the main app page when the plot type of Ensemble Histogram is selected. This can be set to Rank Histogram, Probability Integral Transform Histogram, or Relative Position Histogram. Selecting one of these will produce the corresponding plot, with bins pre-calculated in the MET verification process. As with regular histogram plots, the user has the option of setting the Y-axis mode to either “Relative frequency” or “Number”.

Reliability plots produce a single curve for the chosen parameters (probabilistic variables only), with Forecast Probability on the x-axis, and Observed Relative Frequency on the y-axis. Four additional lines will be displayed on the graph, denoting perfect skill, no skill, x climatology, and y climatology.

ROC plots can display multiple curves (probabilistic variables only), with False Alarm Rate on the x-axis, and Probability of Detection on the y-axis. An additional diagonal line will be displayed on the graph, denoting no skill.

Performance Diagrams can also display multiple curves (probabilistic variables only), with Success Ratio (1-FAR) on the x-axis, and Probability of Detection on the y-axis. Additional solid black curves are displayed on the graph to denote lines of constant bias, and additional dashed black curves are displayed on the graph to denote lines of constant CSI.

Figure 3.12 shows the user interface for defining an Ensemble Histogram and Figure 3.13 through Figure 3.15 show examples of the 3 types of Ensemble Histograms.

Figure 3.16 shows an example Reliability plot, Figure 3.17 shows an example ROC plot, and Figure 3.18 shows an example Performance Diagram, all for the same data set.

## 3.6. Precipitation App

The Precipitation app is designed for plotting scalar and contingency table statistics for variables relating to precipitation.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Region

Statistic

Variable

Threshold

Interp-Method

Scale

Obs type

Forecast lead time

Level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

CSI

FAR

FBIAS

GSS

HSS

PODy

PODn

POFD

FSS

RMSE

Bias-corrected RMSE

MSE

Bias-corrected MSE

ME (Additive bias)

Multiplicative bias

Forecast mean

Observed mean

Forecast stdev

Observed stdev

Error stdev

Pearson Correlation

Plot types available include

Time Series

DieOff

Threshold

ValidTime

GridScale

Histogram

Contour

Plots in the Precipitation app for Time Series, DieOff, ValidTime, Histogram, and Contour are the same as in Upper Air.

A different plot type, Threshold, is present in this app. Threshold plots display threshold on the x-axis, and the mean value of the selected parameter on the y-axis.

Another unique plot type, GridScale, is included in this app. GridScale plots display grid scale on the x-axis, and the mean value of the selected parameter on the y-axis.

Figure 3.19 shows an example of the user interface for the Precipitation app, Figure 3.20 shows an example Threshold plot, and Figure 3.21 shows an example GridScale plot.

## 3.7. Cyclone App

The Cyclone app is designed for plotting track and intensity verification statistics for both tropical and extratropical cyclones.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Basin

Statistic

Year

Storm

Truth

Forecast lead time

Storm classification

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

Track error

X error

Y error

Along track error

Cross track error

Model distance to land

Truth distance to land

Model-truth distance to land

Model MSLP

Truth MSLP

Model-truth MSLP

Model maximum wind speed

Truth maximum wind speed

Model-truth maximum wind speed

Model radius of maximum winds

Truth radius of maximum winds

Model-truth radius of maximum winds

Model eye diameter

Truth eye diameter

Model-truth eye diameter

Model storm speed

Truth storm speed

Model-truth storm speed

Model storm direction

Truth storm direction

Model-truth storm direction

RI start hour

RI end hour

RI time duration

RI end model max wind speed

RI start truth max wind speed

RI end truth max wind speed

RI truth start to end change in max wind speed

RI truth maximum change in max wind speed

Plot types available include

Time Series

DieOff

ValidTime

YearToYear

Histogram

Plots in the Cyclone app for Time Series, DieOff, ValidTime, and Histogram are the same as in Upper Air.

A different plot type, YearToYear, is present in this app. YearToYear plots display individual years on the x-axis, and the mean value of the selected statistic for each year on the y-axis. This is useful for seeing how forecast quality has changed from year to year for each ocean basin.

Figure 3.22 shows an example of the user interface for the Cyclone app, and Figure 3.23 shows an example YearToYear plot.

## 3.8. Objects App

The Objects app is designed for plotting skill scores and model-obs pair verification statistics for convective objects.

For this app, the following parameters have choices derived from the data.

Group

Database

Data-source

Statistic

Variable

Threshold

Radius

Scale

Forecast lead time

Level

Description

Dates

Curve-dates

The selector for the Statistic has these possible choices (depending on available MET line types):

OTS (Object Threat Score)

MMI (Median of Maximum Interest)

CSI (Critical Success Index)

FAR (False Alarm Ratio)

PODy (Probability of positive detection)

Object frequency bias

Model-obs centroid distance

Model-obs centroid distance (unique pairs)

Model-obs angle difference

Model-obs aspect difference

Model/obs area ratio

Model/obs intersection area

Model/obs union area

Model/obs symmetric difference area

Model/obs consumption ratio

Model/obs curvature ratio

Model/obs complexity ratio

Model/obs percentile intensity ratio

Model/obs interest

Plot types available include

Time Series

DieOff

Threshold

ValidTime

Histogram

Plots in the Objects app for Time Series, DieOff, ValidTime, and Histogram are the same as in Precipitation.

Figure 3.24 shows an example of the user interface for the Objects app.