23-HDP

(Released February 2023)

HURRICANE DATA PROVISIONS (HDP)

2023 AND SUCCEEDING CROP YEARS 

These provisions document the procedures for determining the counties where a loss is 

triggered for Hurricane Insurance Protection-Wind Index (HIP-WI) Endorsement and the Tropical 

Storm (TS) Option. The county losstrigger is determined using data provided from the National 

Oceanic and Atmospheric Administration (NOAA) and the U.S. Census Bureau. The data may be 

modified in the Special Provisions of Insurance. 

1. Data 

HIP-WI uses three external datasets to determine a loss trigger: the location and wind field of 

the cyclone are taken from the International Best Track Archive for Climate Stewardship 

(IBTrACS) data, the geometry of the counties, and the counties which are adjacent are from the 

U.S. Census Bureau. The TS Option uses an additional precipitation dataset to determine loss 

triggers from NOAA Climate Prediction Center (CPC). The following table summarizes the 

location of the external data sources. All times for all datasets are Universal Time Coordinated

(UTC). 

Table 1: Cyclone Data Provisions External Data Sources

Data Set Data Location (or successor website)

Cyclone Tracks 

and Wind Extents 

(IBTrACS)

https://www.ncei.noaa.gov/products/international-best-track-archive

US County 

Shapefile

https://www.census.gov/cgi-bin/geo/shapefiles/index.php

US County 

Adjacency

https://www2.census.gov/geo/docs/reference/county_adjacency.txt

Gridded 

Precipitation

https://ftp.cpc.ncep.noaa.gov/precip/CPC_UNI_PRCP/GAUGE_CONUS/

Hurricane and Tropical Storm Track Data 

The data used for determining if a hurricane or tropical storm intersects a county is the IBTrACS 

dataset from the National Climatic Data Center within the National Hurricane Center operated 

by NOAA. The table below shows the variables used to develop the wind extents and 

determine the trigger counties. The 64-knot wind speeds are associated with a hurricane 

weather event, while the 34-knot wind speeds are associated with a tropical storm weather 

event. 
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IBTrACS generally records new values for these variables in three-hour intervals. RMA will use 

all available data from NOAA. If data is missing, RMA will coordinate with NOAA to fill in the 

missing data. If NOAA is unable to provide the missing data, the missing data will be 

interpolated, averaged, or projected using the best available data from NOAA as determined by 

RMA. Data is missing if none of the fields are available. For example, if a quadrant is missing 

from the wind extents, is not considered to be missing if at least one other wind extent is 

available.

County Data 

The county boundary shapefile (TIGER/Line) from the U.S. Census Bureau is used to determine 

if the cyclone corridor intersects the county boundary. Adjacent counties are determined using 

the county adjacency file from the U.S. Census Bureau. Due to the timing of the contract 

change dates, the shapefile and county adjacency file used will have a two-year lag behind the

reinsurance year. Census county boundaries and adjacent counties may be modified by Special 

Provisions of Insurance.

Rainfall Data 

The precipitation dataset used to determine the county rainfall is the CPC Unified Gauge-Based 

Analysis of Daily Precipitation over Continental United States (CONUS). This is a 0.25-degree

latitude by 0.25-degree longitude grid of precipitation. The rainfall of a county is determined by 

the weighted mean of the fractional area that each grid cell contributes to the county’s rainfall 

based on the U.S. Census Bureau shapefile.

2. Hurricane and Tropical Storm Wind Corridor Construction 

The hurricane and tropical storm wind corridors are constructed in the same manner. For 

hurricanes, the 64-knot wind extents are used, and for tropical storms, the 34-knot wind 

Variable Column Name Units

Season SEASON Year

Name NAME N/A

Time ISO_TIME UTC (YYYY-MM-DD HH:MM:SS)

Latitude USA_LAT Degrees North

Longitude USA_LON Degrees East

Maximum Sustained Winds USA_WIND Knots

Hurricane Category USA_SSHS Saffir-Simpson Wind Scale

Wind Extents Northeast USA_R64_NE / USA_R34_NE Nautical Miles

Wind Extents Southeast USA_R64_SE / USA_R34_SE Nautical Miles

Wind Extents Southwest USA_R64_SW / USA_R34_SW Nautical Miles

Wind Extents Northwest USA_R64_NW / USA_R34_NW Nautical Miles
3 

extents are used. This section will provide the methodology used to determine the cyclone 

center points, wind extent buffers, and cyclone corridors. The wind corridor is used to 

determine which counties the storm intersects. The wind corridor is constructed from convex 

hulls of the wind buffer radii which are centered around the storm center points.

HIP-WI TS Option

Wind Threshold USA_WIND >= 64 USA_WIND >=34

Wind Extents(Cyclone Buffer) USA_R64_NE, USA_R64_SE, 

USA_R64_SW, USA_R64_NW

USA_R34_NE, USA_R34_SE, 

USA_R34_SW, USA_R34_NW

Storm Center Points 

IBTrACS uses World Geodetic System 1984 longitude and latitude coordinates which locate the 

center of the cyclone. When wind speeds reach or exceed 64 knots (USA_WIND >= 64), the 

storm center point is a hurricane center point. In addition, RMA will calculate a hurricane 

center point between the last tropical storm center point and the first hurricane center point 

(i.e., when a tropical storm strengthens to a hurricane) and another hurricane center point 

between the last hurricane center point and the first tropical storm center point (i.e., when a 

hurricane weakens to a tropical storm). A tropical storm center point by itself does not

constitute a hurricane center point for determining a county loss trigger. 

Tropical storm center points will be determined in a similar manner. When wind speeds reach 

or exceed 34 knots, the storm center point is a tropical storm center point. RMA will calculate 

an interpolated tropical storm center point between transitions to a tropical depression and 

from a tropical depression. A tropical depression center point by itself does not constitute a 

tropical storm center point for determining a county loss trigger.

Wind Buffer Creation 

The maximum of the 34-knot or 64-knot wind radii extents are used to determine a buffer 

around the cyclone. The wind radii extents describe the maximum distance at which the given 

wind speed existed in the four quadrants (northeast, northwest, southwest, southeast). The 

maximum over the quadrants is used for the buffer.

Hurricane Buffer = MMaaaa(UUUUUU_RR64_NNNN,UUUUUU_RR64_ ,UUUUUU_RR64_ SS,UUUUUU_RR64_NN )

Tropical Storm Buffer = MM (UUUUUU_RR34_NNNN,UUUUUU_RR34_ ,UUUUUU_RR34_ SS,UUUUUU_RR34_NN )

Example: 

Suppose the maximum distance of the hurricane wind extents from the storm center point 

is 35 nautical miles (nm) for the northeast quadrant, 25 nm for the southeast quadrant, 10 

nm for the southwest quadrant, and 30 nm for the northwest quadrant. In this case, the 

maximum distance of the hurricane wind extents from the storm center is 35 nm 
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(northwest quadrant). The hurricane buffer is then a 35 nm radius circle around the storm 

center point.

Estimated Hurricane and Tropical Storm Center Point and Buffer 

A hurricane ceases to exist at some point between where the last hurricane center point is 

measured and when the first tropical storm center point is measured. The maximum sustained 

winds (USA_WIND) value is used to calculate where the estimated hurricane center point and 

wind extents are measured. For purposes for this document, a similar calculation is made for a 

tropical storm to and from a depression or to and from a hurricane. The term transitional 

cyclone centerpoint is used when transitioning between hurricanes, tropical storms and tropical 

depressions.

The estimated cyclone center point and buffer are calculated based on the last cyclone center 

point (USA_LAT and USA_LON) and maximum sustained wind speeds (USA_WINDhurr) and the 

transitional cyclone center point (USA_LAT and USA_LON) and maximum sustain wind speeds 

(USA_WINDts). The following examples are when a hurricane transitions to a tropical storm, but 

similar calculations are used between a tropical storm and a tropical depression.

A bearing is calculated between the two cyclone center points and the bearing and distance 

(Distancefull) is used to calculate the estimated center point. The distance is calculated using 

the following formula: 

Distance = DDDDDDDD DDDDDDffffffff ∗ UUUUUU_WWWWWWWWhuuuuuu−64

UUUUUU_WWWWWWWWhuuuuuu− UUUUUU_WWWWWWWWttss

The estimated buffer is calculated using the last hurricane buffer (HurricaneBufferlast) and the 

following formula:

Buffer = MM (

HH HHHHHHHHHHHHHHHH HHHHllll

2 , HHHHHHHH HHHHHHHH HH llll ∗ (1 − UUUUUU_WWWWWWWWhuuuuuu−64

UUUUUU_WWWWWWWWhuuuuuu− UUUUUU_WWWWWWWWtt

))

A similar calculation is used during the formation of a hurricane, using the last tropical storm 

center point and the first hurricane center point, or the formation of a tropical storm using the 

last tropical depression center point and the first tropical storm center point. 

Example:

Given the table below:
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The last hurricane center point occurs on September 30th at 0:00 hours and the first tropical 

storm center point occurs on September 30th at 3:00 hours. The maximum sustained wind 

speeds are 70 knots and 60 knots, respectively. Figure 1 below shows the estimated 

hurricane center point and buffer.

A depiction of an estimated center point and cyclone buffer for a fictional cyclone is provided 

below in Figure 1. 

Figure 1: Example Estimated Center Point and Buffer for Fictional Cyclone

SEASON NAME ISO_TIME USA_LAT USA_LON USA_SSHS USA_WIND USA_R64_

NE

USA_R64_

SE

USA_R64_

SW

USA_R64_

NW

2020 HURRICANE 9/29/20 0:00 21.3000 -74.0000 0 60 

2020 HURRICANE 9/29/20 3:00 21.6999 -74.5877 1 65 15 

2020 HURRICANE 9/29/20 6:00 22.1000 -75.1000 1 70 25 15 20

2020 HURRICANE 9/29/20 9:00 22.5072 -75.5228 1 75 30 15 15 20

2020 HURRICANE 9/29/20 12:00 22.9000 -75.9000 1 80 35 25 10 30

2020 HURRICANE 9/29/20 15:00 23.2574 -76.3003 1 90 35 20 11 30

2020 HURRICANE 9/29/20 18:00 23.6000 -76.7000 1 80 30 20 11 25

2020 HURRICANE 9/29/20 21:00 23.9649 -77.1001 1 75 20 15 20

2020 HURRICANE 9/30/20 0:00 24.3000 -77.5000 1 70 10

2020 HURRICANE 9/30/20 3:00 24.5650 -77.9152 0 60
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Cyclone Corridor Construction 

When the cyclone center points and corresponding cyclone buffers are plotted, the result is a 

series of (often overlapping) circles. A convex hull is calculated for each pair of adjacent buffers

which results in a series of ovals. Figure 2 below shows the convex hulls for the adjacent 

buffers. A corridor is then made of all the convex hulls of a cyclone and is used to determine 

the county intersections. The county intersections and triggers for the HIP-WI Endorsement 

(excluding the TS Option) are described in Section 3.

Figure 2: Example of Convex Hulls for Fictional Cyclone

3. Determining County Loss Triggers for HIP-WI (Excluding TS Option)

Once the convex hulls are calculated, county loss triggers are determined. The convex hulls and 

the county shapefile are mapped in the same coordinate reference system. Any county shape 

that intersects the convex hulls meets the county loss trigger. Any county that is adjacent 

(according to the U.S. Census Bureau County Adjacency File) to a county that is intersected by 

the convex hulls will also meet the county loss trigger.

The county loss trigger and date will be published in the actuarial documents. The date will be 

the date that the cyclone corridor intersects the county for direct triggers, or the first date that 

the county was indirectly triggered. 
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Payments will be issued in accordance with the HIP-WI Endorsement. NOAA publishes IBTrACS 

datasets approximately two weeks following the occurrence of a hurricane landfall. Once 

published, RMA will obtain the IBTrACS dataset and determine whether a county is triggered. If 

NOAA publishes an updated final IBTrACS dataset following the hurricane season, RMA will 

process the updated data to determine if any additional counties are triggered. Counties 

previously identified as being triggered, will remain triggered.

RMA will use the R programming language to implement these provisions. Sample computer 

code to determine triggered counties can be found at: 

https://www.rma.usda.gov/Topics/Hurricane-Insurance-Protection-Wind-Index. 

4. NOAA CPC Gridded Rainfall 

The precipitation data set used is the NOAA Climate Prediction Center (CPC) Unified GaugeBased Analysis of Daily Precipitation over the continental United States (excluding Alaska and 

Hawaii). The grid is 0.25-degree latitude by 0.25-degree longitude, a square approximately 16 

miles in length. Additional information of the grid is available at: 

https://ftp.cpc.ncep.noaa.gov/precip/CPC_UNI_PRCP/GAUGE_CONUS/DOCU/PRCP_CU_GAUGE

_V1.0CONUS_0.25deg.README (or successor website).

The gridded dataset is converted into a county average precipitation by determining the area 

that each grid intersects the county shapefile, and then calculating a weighted average of the 

area and grid rainfall for a 4-day period. The period used for the TS Option is the day the 

cyclone corridor intersects the county, plus a 1-day lag (prior day) and a 2-day lead (subsequent 

days), with a threshold of 6 inches.

A fictious example for Pi County, is shown below. Four grids intersect the county and their 

cumulative precipitation over a period of 4 days is shown below. The weighted average for the 

county is shown in the table below.
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Grid Area

Rainfall 

Lag Day

(in.)

Rainfall

Wind Intersect Day

(in.)

Rainfall 

Lead Day 1

(in.)

Rainfall 

Lead Day 2

(in.)

Total

4-day Period

(in.)

A 25 0.2 1.0 2.5 2.0 5.7

B 25 1.0 1.0 3.0 1.5 6.5

C 25 0.0 1.0 2.0 2.0 5.0

D 25 0.3 1.0 3.0 3.0 7.3

Weighted 

Average

0.375 1.0 2.625 2.125 6.125

The weighted average for Day 1 is determined as the area of grid A times the rainfall amount of 

grid A plus the area of grid B times the rainfall amount of grid B and so on, divided by the total 

area. For Day 1 it is (25 × 0.2 + 25 × 1 + 25 × 0.0 + 25 × 0.3) / (25 + 25 + 25 + 25) = 0.375. The 4-

day cumulative rainfall is 0.375 + 1.0 + 2.625 + 2.125 = 6.125 in.

5. Determining County Loss Triggers for the TS Option 

A tropical storm triggers occur when:

1. The 34-knot corridor intersects the county;
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2. Precipitation in the county equals or exceeds 6 inches during a four-day interval (the 

day the 34-knot corridor intersects the county, the preceding 1 day (lagging) and the 

following 2 days (leading); and

3. No hurricane trigger occurs.

A county can be triggered directly or through county adjacency (according to the U.S. Census 

Bureau County Adjacency File). A direct trigger occurs when the triggering requirements are 

satisfied; an indirect trigger occurs when the county is adjacent to a county that is directly 

triggered.

The county loss trigger and date will be published in the actuarial documents. The date will be 

the date that the cyclone corridor intersects the county for direct triggers, or the first date that 

the county was indirectly triggered. Payments will be issued in accordance with the TS Option. 

NOAA publishes CPC data daily and IBTrACS datasets approximately two weeks following the 

occurrence of a cyclone landfall. Once published, RMA will obtain the datasets and determine 

whether a county is triggered. 

If NOAA publishes an updated final IBTrACS dataset following the hurricane season, or if CPC 

data is modified in accordance with Section 8 of the HIP-WI Endorsement, RMA will process the 

updated data to determine if any additional counties are triggered. Counties previously 

identified as being triggered will remain triggered.

6. Hurricane and Tropical Storm Option Trigger (Fictitious Example) 

The figure below is used to demonstrate different scenarios where counties and adjacent 

counties will be triggered under the HIP-WI Endorsement and TS Option. Wind speeds (either 

hurricane or tropical storm) are noted by either an HU (hurricane) or TS (tropical storm) within 

the hexagonal county shape. 
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Hurricane Triggers 

Counties and adjacent counties triggered by a hurricane under the HIP-WI Endorsement are 

shown in shades of green. The dark green counties are triggered by sustained hurricane force 

winds of 64 knots or greater as determined by NOAA and in accordance with these HDP. The 

light green counties are triggered because they are adjacent to the directly triggered counties in 

accordance with the U.S. Census Bureau adjacency file.

Tropical Storm Option Triggers 

Blue raindrops signify counties which equaled or exceeded the 6 inches of cumulative 

precipitation. Counties filled in with blue or light blue are Tropical Storm Option triggers. 

Several distinct trigger scenarios are described below.

1. County 18 is triggered as an adjacent HIP-WI hurricane trigger, so it is due a full 

indemnity. It also experienced sustained tropical storm force winds and received at 
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least 6 inches of cumulative rain. Therefore, it triggers its adjacent counties (12, 9, and 

25) under the TS Option.

2. County 9 received sustained tropical storm force winds and at least 6 inches of 

cumulative rain, which triggers itself and its adjacent counties (2, 3, 8, and 15).

3. County 8 was triggered due to its adjacency to County 9. It also received 6 inches of 

cumulative rainfall. However, since it did not receive sustained tropical storm force 

winds, it does not trigger any additional adjacent counties.

4. County 20 received 6 inches of cumulative rainfall but did not receive tropical storm 

force winds. Therefore, it does not trigger itself, nor its adjacent counties. 

5. Counties 5, 21, 27, and 31 all received sustained tropical storm force winds, but did not 

receive at least 6 inches of rainfall and therefore do not trigger themselves or adjacent 

counties.