The TCTR (Tropical Cyclone Threat Rating) is similar to Force Thirteen's CDPS (Cyclone Destruction Potential Rating). It is a way of measuring a storm's potential impact on land. It takes into account Rainfall and Storm surge potential among with the wind threat. Based on that, a rating of 0-20 is assigned based on the danger the storm poses. The TCTR has 4 categories: Wind Threat: The storms wind potential on land Rainfall Potential: The amount of rain expected Storm Surge Threat: The potential storm surge Other Factors/Overall Threat: Other factors like storm size, population, poverty in the area To calculate a storm's TCTR, you will need: -The data for a storm -A piece of paper -A Calculator (unless you want to do the math in your head or on the paper) STEP 1: Find the threat amounts Find the value for each of the categories and write it down on your paper Wind: The expected wind in mph. If the expected wind is less than 35 mph, just put 35. If the expected wind is higher than 200 mph, just put 200. Rain: The highest expected rain in inches. If the expected rainfall tops 65 inches, just put 65 Storm surge: The highest storm surge induction expected, in feet. If the forecast tops 30 feet, just put 30. Other factors/Overall Threat: This is the most abstract one and if you get a different value than me, it is likely because you interpreted this differently. This is a number between 1 and 25 that considers how the area will fare. The more people affected, the higher. Also, numbers may be adjusted if: -The area is not/very well prepared -The area is poor -The area has been impacted by other disasters recently Now that you have these numbers, its time for step 2 STEP 2: Calculate the raw sector rating Now, you'll need your calculator. Take the 4 values and put them in the equation as v. Write down the result of the equation. With the exception for rainfall, where the number may go up to 27.27, the number should not be higher than 25. -Wind: (v-35)/6.6 -Rain: v/2.2 -Storm Surge: v/1.2 -Other Factors: Keep the value the same The number you got is the raw sector rating. Based on this, you can find the category for each threat (This is optional). 0-3: Minor (1) 4-8: Considerable (2) 9-14: Significant (3) 15-18: Major (4) 19-25: Extreme (5) STEP 3: Calculate the final TCTR Now, use your calculator to find the average of these 4 values. You can doing this by adding them together and dividing it by 4. This is the average sector score. Now round this score to the nearest whole number. This is the TCTR value (The TCTR does not go over 20. If the value is between 21-26, the rating is 20). Here is what the damage is expected to be based on the rating: 0: None 1-3: Minor 4-5: Limited 6-7: Considerable 8-11: Significant 12-14: Major 15-20: Catastrophic 18-20: Extreme 20: Total Why a TCTR of 20 is so rare: A TCTR of 20 means that total damage is expected. Since 2010, only 2 storms have achieved a stage 20, those being Haiyan (2013) and Dorian (2019). In order for a storm to achieve a TCTR of 20, it needs to have all four categories reach a Raw Sector Rating of 20, or have one substitute for another. Here are the lowest values for a TCTR of 20 (Note: One value may be lower if another makes it up) Wind: 167 mph Rain: 44 in Storm Surge: 24 feet Other Factors: 20
