Tropical Storm Gabrielle - 14 September 2001
moving across central Florida

WSR-88D Tropical Cyclone Operations Plan

Suggested by the Tropical Prediction Center (TPC/NHC) and WFO Melbourne, FL
Current for Open RPG system;  11/03/02

• This plan was designed to be used as an operational reference only. Local modifications to the plan will likely be required. Be sure to consult with your local Unit Radar Committee (URC) in advance concerning any changes which result in system wide modifications. Pre-hurricane URC agreements will allow changes to be made operationally as needs arise.

 
• It is important to note that the 8-level 0.54 nm Velocity product and the 0.54 nm Composite Reflectivity product are not available to Class 2 Users (NAPUPs) according to the baseline product set defined in the current Guidance on Adaptable Parameters (WSR-88D Handbook Volume 1, RPG). These products can be made available by modifications to the RPG Product Generation Table Editor and RPG Product Distribution Control table (step 4, below). While temporary additions of these products can by made on-site, each time the RPG is rebooted or the VCP/weather mode is changed, the list will be replaced with the baseline. Therefore, it is suggested that the site request the ROC Hotline to make the product additions to the baseline for the duration of the tropical event.

• The most important part of this plan for both Class 1 Users (APUPs) and Class 2 Users (NAPUPs) is the availability of and changes associated with the 8-data level Velocity product (steps 3, 4, and 11). The advantage of using the 8-level Velocity product is that the maximum wind field can be displayed, while leaving the standard 16-level Velocity product (-64 kt to +64 kt) alone for routine use.

 
• Note your local "default" adaptable parameters before implementing any changes. After the tropical cyclone threat has passed, return all parameters back to their proper "default" values. Refer to the current Guidance on Adaptable Parameters (WSR-88D Handbook Volume 1, RPG) for system wide defaults.

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• "Levels of change authority" require steps 4 and 11 to be performed for the WFO by the ROC Hotline. Ensure a telephone line is available to your MSCF's modem, and allow up to a half hour for the ROC Hotline to make the changes (i.e. contact the ROC Hotline well prior to rainband impact). All other changes are performed by the WFO using the URC level of change authority. Once the tropical cyclone event has passed, contact the ROC Hotline to return ROC password controlled adaptable parameters to their default values.

 
• For questions or comments, please contact: Scott Spratt; NWS Melbourne, FL or Colin McAdie; Tropical Prediction Center (TPC/NHC).

At the WSR-88D RPG Human Computer Interface (HCI):

All commands for steps 1-12 begin from the HCI RPG Control/Status window and may require URC level password. Steps 4 and 11 require URC level passwords and the ROC hotline must be contacted.

1. Well prior to the onset of tropical cyclone rainbands, ensure that the RDA emergency power generator fuel level is maximized.  It may be several days before commercial power is restored in the aftermath of a significant tropical cyclone and fuel delivery will likely be delayed.

From the Applications menu, select RDA Performance Data, then select Tower Utilities
(check % of Gen Fuel Level)

2. Operational mode - Use VCP 11 for better vertical resolution and faster data refresh. A switch to VCP 21 can be made if load shedding becomes a concern.

Select VCP Control Panel/Window, then select CHANGE to RDA VCP: 11(note: wait until 0.5 degree scan completes before executing the command).
Confirm and Close

This command invokes a "local" VCP as defined in the RDA adaptation data. Local VCP 11 (and 21) are defined with a .97 kt Velocity Measurement Increment (VMI) which limits velocity measurements to ±123 kt and a 5 PRF selection which restricts the unambiguous range to 79 nm. To modify the unambiguous range to 94 nm, or to change the VMI to measure winds in excess of ±123 kt, refer to steps 10 and 11, respectively.

3. Velocity data (display) levels for the 8-data level products should be set to display hurricane force winds. Note the default settings for the 16-data level Velocity products display a maximum of 64 kt, which will be exceeded by even a minimal Category 1 hurricane. Begin with the suggested values, then adjust accordingly to best display the maximum wind field.

From the RPG Products menu, choose Selectable Parameters, then select Category: Velocity Data Levels
Select Velocity Table Precip 8 / 0.97 and change Code 7 to 100 and Code 6 to 80
Select Velocity Table Precip 8 / 1.94 and change Code 7 to 135 and Code 6 to 115
Save, select Update, confirm changes, and Close

This modifies the 8-level Velocity products ONLY. The routine 16-level Velocity products are not affected. By entering the values above, corresponding negative values are automatically supplied.

Table "Precip 8 / 0.97" ("Precip 8 / 1.94") will be used if the Velocity Measurement Increment (VMI) is .97 kt (1.94 kt). Refer to step 11, below.

4. Allow Non Associated PUPs (National Centers such as TPC) access to:

 a.) 8-data level 0.54 nm Velocity (V) product (product #24)

 b.) 0.54 nm Composite Reflectivity (CR) product (product #37)

These products should be added to the Precip Mode (Adaptation List A) RPG Product Generation Table.
 

*** NOTE: This change requires ROC level of change authority - contact the ROC Hotline. While these changes can be made to the Current RPG Product Generation list using URC level of change authority, any RPG reboot or weather mode change will restore a "default" Adaptation list, removing the product #24 and #37 additions. ***

From the RPG Products menu, select Generation List to obtain the RPG Product Generation Table Editor list.
Select Precip Mode (A)
Change the Code #24 (Base Velocity: 8 level/0.54 nm) row as follows: Gen to 1, Arc to 0, Sto to 1, (mins) to 60, and cut(s) to -4
Change the Code #37 (Composite Refectivity: 16 level/0.54 nm) row as follows: Gen to 1, Arc to 0, Sto to 1, and (mins) to 60
Save and Close
Select Replace Current Table with: Precip Mode (A)

5. The Threshold Pattern Vector (TPV) within the Mesocyclone algorithm should be reduced to 6 to improve detection of small diameter features; however, a greater number of false alarms will also be generated. NOTE: the Mesocyclone and Tornado Detection algorithms began to process data separately starting with WSR-88D build 10. Steps 5 and 6 will independently increase the detection efficiency of small, shallow circulations.

From the RPG Products menu, choose Algorithms, then select Adaptation Item: Mesocyclone
Change Min # Pattrn Vec value from 8 to 6
Save, Update, confirm changes, and Close

6. Several "default" parameters within the Tornado Detection Algorithm (TDA) should be reduced to increase the probability of detecting weak or distant tornadoes; however, a greater number of false alarms will also be generated. The values indicated below were derived from the ROC suggested "tropical cyclone" parameter set.

From the RPG Products menu, choose Algorithms, then select Adaptation Item: Tornado Detection
Change Minimum 3d Feature Depth from 1.5 to 2.0
Change Min 3d Feat Low-Lvl Delta Vel from 25 to 14
Change Minimum TVS Delta Velocity from 36 to 44
Save, Update, confirm changes, and Close

7a. Change the "default" (convective) Z/R relationship (300R^1.4) to the "tropical" Z/R relationship (250R^1.2) to provide better precipitation estimates. NOTE 1: closely monitor rainfall accumulations relative to ground truth observations. If the Z/R relationship is changed too far in advance of the tropical cyclone rainbands, the radar will overestimate totals associated with pre-landfall convection. NOTE 2: An AWIPS program can be run in real time to create parallel versions of radar precipitation products using different Z-R relationships; i.e.  you can create OHP, THP and STP products locally on AWIPS with the tropical Z/R and compare them in real time with the (default Z/R) products from the RPG.

From the RPG Products menu, choose Algorithms, then select Adaptation Item: Hydromet Rate
Set Z-R Multiplier Coef. [CZM] to 250
Set Z-R Exponent Coef. [CZP] to 1.2

7b. If your site has been authorized by the ROC to change the MXPRA (Maximum Precipitation Rate Threshold), the parameter should be increased to allow for greater rain rates. A MXPRA of 200 mm/hr (7.9 in/hr) should be sufficient during most tropical cyclone situations [the ROC recommends that the MXPRA never be set higher than 200 mm/hr (7.9 in/hr)]. If the MXPRA is not adjusted, the default value will only allow for a maximum rate of 103.8 mm/hr (4.1 in/hr).

Set Max Precipitation Rate to 200 mm/hr (7.9 in/hr)
Save, Update, confirm changes, and Close

8. Ensure that minimal clutter suppression is in effect. This will improve rainfall estimates and overall algorithm performance. If significant clutter or anomalous propagation (AP) becomes apparent, return to a greater Clutter Suppression Region file.

From the Applications menu, select Clutter Regions
Select File, then double-click on 11 (assuming clutter suppression region 11 is a pre-built minimal suppression file)
Close, then select Download

If you need to "build" (then download) a minimal CSR, the following commands will produce one with the bypass map in control and with medium suppression applied to known ground targets.

From the Applications menu, select Clutter Regions
Select File, then double-click on Default
Edit both the Segment: Low and Segment: High tables to agree with the one below.
Save, Close, then Download
 

Example of a minimal Clutter Suppression Region (file 11) - Bypass map in control

Region:	Azi1 (Deg)	Azi2 (Deg)	Ran1 (NM)	Ran2 (NM)	Select Code	Dopl Chan	Surv Chan
1	0	360	1	275	Bypass Map	Medium	Medium

9. Adjust precipitation data display levels if the potential for extremely heavy rainfall exists [maximum displayable values: 12.7 inches for One Hour Precipitation (OHP) and Three Hour Precipitation (THP), and 25.4 inches for Storm Total Precipitation (STP) and User Selectable Precipitation (USP)].

From the RPG Products menu, choose Selectable Parameters, then select Category: OHP/THP Data Levels
Change Codes 3 through 16 as desired for the current event
Save, select Update, and confirm changes
Select Category: STP Data Levels
Change Codes 3 through 16 as desired for the current event
Save, select Update, confirm changes, and Close

10. Remember that RPG HCI operators have the ability to move the maximum unambiguous range (R_max) out to a maximum distance of 94 nm or in to a minimum distance of 63 nm by adjusting the PRF. This may become necessary to improve velocity products as the tropical cyclone approaches. The "Download" command invokes a "Remote" VCP, with VCP 11 (and 21) defined with a PRF of 4 (R_max = 94 nm). NOTE: the TPC prefers the maximum R_max as often as possible. However, local needs may dictate otherwise, and will take precedence.

Select RDA Control
Select VCP in the Control/Status window
Toggle Auto PRF Off
Under Download VCP from RPG, select 11
Confirm and Close

Note: wait until the 0.5 degree scan completes before executing the download command. As long as the Auto PRF is off, the unambiguous range will remain at 94 nm.

11. If velocities are expected to exceed 124 kt, increase the Velocity Measurement Increment (VMI) from .97 kt to 1.94 kt.
 

*** NOTE: This change requires ROC level of change authority - contact the ROC Hotline. While these changes can be made to the Current VCP, whenever other changes are made to the VCP, the original VMI will be restored. ***

With the Auto PRF remaining Off...
Select RDA Control
Select VCP in the Control/Status window
For Modify VCP: select Adaptation
Toggle Velocity Increment to 1.94 kts
Save, Download, confirm changes, and Close
Verify PRF #4 (R_max = 94 NM) remains set for all sectors

Note 1: If the VMI is .97 kt (1.94 kt), Table "Precip 8 / 0.97" ("Precip 8 / 1.94") from step 3 above applies for the 8 data level Velocity products. Note 2: All coastal sites have been authorized to make this change to adaptation VCP 11 (and 21).

12. Reset the precipitation products to begin accumulating rainfall at the onset of the Tropical event. To accomplish this, the Nominal Clutter Areas (NCA) should be adjusted temporarily to 80000 km².

Select Precip Cat and note the values of 'Detect' for each of the three categories.
Select Modify Parameters, click within the 'NCA' box for the first 'Tilt Domain', select Modify, change the value to 80000, and select Apply.
Next, click within the 'NCA' box for the second 'Tilt Domain', select Modify, change the value to 80000, and select Apply.
Finally, click within the 'NCA' box for the last 'Tilt Domain', select Modify, change the value to 80000, and select Apply.
Save, confirm, and Close.

Note: One hour must now elapse before the precipitation products will be reset (monitor the "Time Until Clear Air" line within the 'Precipitation Status' window). Once the clock reaches "0" minutes and the preciptation products reset, remember to re-adjust the NCA's back to minimal values.

Alternate method (since one or two volume scans of data will be lost due to an RPG reboot, ensure this step is performed prior to any weather concerns):

From the RPG Control Panel, click Off under Shutdown, then click Options under Restart.
Select Hydromet, then Activate.
Close Options Window, then select All Tasks under Restart.

13. Make certain that the ARCHIVE II and III devices remain active. For non-collocated RDA/WFO sites, plan ahead to ensure the ARCHIVE II jukebox is loaded with new tapes. It is best to load a new ARCHIVE III disk.

From AWIPS:

14. It is strongly encouraged that local data archival is performed.

15. Initiate "radar multiple requests" to adjacent radar sites. Continuously monitor adjacent sites since significant tropical cyclone phenomena are based in the lower levels, and the closest radar will sample the environment best.

16. A set of suggested "minimum RPS lists" were originally developed when RPS lists were confined to only 20 products. However, the fundamental philosophy remains the same as operators interrogate tropical cyclones based on range from the radar and intensity. Ensure that your WSR-88D RPS list on AWIPS includes the products on the suggested list (above).

Also, Storm Relative Velocity products (SRR, SRM) should be generated often via One-Time Requests with individual or field motions manually input by the radar operator. The algorithms may not be able to produce a useful motion on their own due to the rotational aspects of tropical cyclones.

NOTE: These suggested guidelines will be updated when necessitated by WSR-88D software changes. For most recent version, see http://www.srh.noaa.gov/mlb/ntltcops.html

Acknowledgments: RPG HCI procedural input provided by Scott Spratt and Dave Sharp, WFO Melbourne, FL. Suggested Minimum RPS lists provided by Stacy Stewart; Tropical Prediction Center (TPC). TPV and TVS adaptable parameter thresholds suggested by Robert R. Lee; NEXRAD - Radar Operations Center (ROC) Applications Branch. The alternate Z/R AWIPS Program was written by Paul Jendrowski; WFO Blacksburg, VA. Helpful suggestions offered by Joe Chrisman; (ROC) and the Field Support Team have been added.