A Gridded TCM Drill (also a WES case)

The Procedures for Populating WFO-Generated Wind Forecast Grids for
Tropical Cyclone Events appear in NWS Directive 10-601. For quick
reference, the procedures for populating GFE grids within the 34-kt wind
radii appear in the Appendix of this drill, and in the Forecasting
Handbook in the Operations area.

As you are probably aware, these procedures are short-term solutions to
be followed by all impacted WFOs for populating WFO wind grids for
tropical cyclones. Updates to NWS Directive 10-601 will take place as
better methods for populating WFO-generated wind forecasts are
integrated into the Interactive Forecast Preparation System.

Tropical cyclone wind radii (34-, 50-, and 64 kts) are constructed by
NHC forecasters to reflect the strongest wind expected in each quadrant
\[NE, SE, SW, NW (centered on the storm center and relative to north)\].
The TCM grids are then constructed according to these radii and the
projected path of the storm at 6-hr increments. The TCM grids appear in
D2D and also appear as D2D grids in GFE, and should arrive within
minutes of the text products.

**Objectives of this drill:**\
1) Understand uncertainties in TCM forecasts and limitations of
four-quadrant wind radii.\
2) Understand 2003 methodology for populating IFPS/GFE wind grids
containing a tropical cyclone.\
3) Learn from examples using gridded TCM as guidance.\
4) Understand effects of temporal interpolation of gridded TCM in GFE.

This drill is to be performed under the direction and supervision of the
tropical team coordinator, IFPS focal point, or SOO. It should take no
more than one to two hours to complete. Please coordinate a time block
with one of these individuals. It will take a few minutes to setup and
make the gridded TCM files available to GFE.

On a Linux terminal, preferably using the nasr1 training workstation and
the offline GFE software, start GFE. However, the drill can be
accomplished on the operational LX1 GFE software, but care must be taken
**not** to *save* any files.

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**The Drill!**

> Name\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
>
> Date\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

We have hurricane Duval, a Category 3 storm, and possibly a Category 4
when it reaches open water again, predicted to cross the Florida
peninsula with little change in intensity, and break out into the Gulf
of Mexico and move ashore near Apalachicola.

1\. Using the Weather Element Browser, populate d2d wind grids using
TPCtcm at 26/0600. Demonstrate to trainer\_\_\_\_\_\_\_\_(initials).

a\. Can you edit d2d
grids?\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

b\. What are the units of the d2d wind
grids?\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

c\. Copy and paste three 6-hour TCM d2d wind grids (beginning with grid
time where center is near Cedar Key) into the corresponding (time) IFP
wind weather element grids.
Demonstrate\_\_\_\_\_\_\_\_\_\_\_\_\_(intials).

2\. Review rules for populating wind grids for tropical cyclone events
are found in the Appendix and in NWS Directive 10-601.

In the 0 to 24-hour time frame, the procedures state that the GFE wind
grids will show a full continuum of values (at exposed marine locations)
up to the maximum sustained wind value provided by the tropical cyclone
centers.

a\. We will edit the first wind grid where the hurricane center has left
the central Florida coast. For our purposes, it is the 30-hr forecast.
According to the NWS 10-601 procedures, and using your understanding of
mesoscale features over land and water, adjust and edit the wind grids.
Demonstrate\_\_\_\_\_\_\_\_\_\_\_\_\_(initials).

b\. Have you entered winds in the region beyond the TCM wind envelope?
Using any information available to you, populate the region of zero wind
speeds. What and how did you populate that region?

c\. Populate next 6-hr time grid. This is the 36-hr forecast. Edit and
adjust as in 2a.

Demonstrate \_\_\_\_\_\_\_\_\_\_\_\_\_\_(initials).

d\. Interpolate for the times in between the 30- and 36-hr forecasts.
Describe the results of the interpolation.

3\. Populate the next wind grid time, 6 hours later. This is now the
42-hr grid. Edit the wind grid according to the NWS 10-601 procedures,
and using your understanding of mesoscale features over land and water.
Interpolate between 36 hrs and current time.

Demonstrate\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_(initials).

4\. Between 73 and 120 hours, the winds must be capped at
**\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**.

a\. Why do you think there is a cap at this wind speed?

b\. The TPC issues the TCM grids for what time periods?

5\. Between 121 and 168 hours, the winds must be capped at
**\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**.

6\. Please add any comments or concerns about the gridded TCM product as
well as the procedures developed for populating the GFE wind grids.

This concludes the Drill. Thank you for your patience.

# APPENDIX

Procedures for Populating WFO-Generated Wind Forecast Grids for Tropical
Cyclone Events.

Wind Speed Values Within the 34 kt Wind Radii

**0-24 hours (up to the maximum sustained wind)**

Use wind forecast from the TCM (gridded if available) as guidance for
locating the 34-, 50- and 64-kt wind radii to maintain synoptic
consistency. Apply local knowledge and mesoscale expertise to produce
explicit/deterministic wind speed forecasts for all CWA/MAR grids using
a full continuum of values up to the maximum sustained wind value
provided by tropical cyclone centers.

**25-36 hours (up to capped value of 64 kts)**

Use wind forecast from the TCM (gridded if available) as guidance for
locating the 34-, 50- and 64-kt wind radii to maintain synoptic
consistency. Apply local knowledge and mesoscale expertise to produce
explicit/deterministic wind speed forecasts for all CWA/MAR grids using
a full continuum of wind speeds up to 64 kts. For 64 kts and above use
the capped value of 64 kts for grid points inside the 64 kt wind radii.

**37-72 hours (up to capped value of 50 kts)**

Use wind forecast from the TCM (gridded if available) as guidance for
locating the 34 kt and 50 kt wind radii to maintain synoptic
consistency. Apply local knowledge to produce explicit/deterministic
wind speed forecasts for all CWA/MAR grids using a full continuum of
wind speeds up to 50 kts. For 50 kts and above use the capped value of
50 kts for grid points inside the 50 kt wind radii.

**73-120 hours (up to a capped value of 34 kts)**

Use forecast from the TCM as guidance for locating the center positions
to maintain synoptic consistency. During Hurricane Hotline Conference
Call coordinate the best means of determining the 34 kt radii
(extrapolation of 34 kt radii from 72 hour, model guidance, coordination
consensus, etc.). Apply local knowledge to produce
explicit/deterministic wind speed forecasts for all CWA/MAR grids using
a full continuum of wind speeds up to 34 kts. For 34 kts and above use
the capped value of 34 kts for grid points inside the 34 kt wind radii.

**121-168 hours (up to a capped value of 30 kts)**

Use traditional guidance and WFO discretion to produce
explicit/deterministic wind speed forecasts for all CWA/MAR grids using
a full continuum of wind speeds up to 30 kts. The choice for 30 kts
avoids potential confusion which can result from the automated rounding
of 33 kts to 35 kts when generating graphical wind barbs, and with
associated textual formatters which convert kts to miles per hour (then
round to the nearest 5 mph).