Severe thunderstorms can be life-threatening, but not all severe storms are the same. Hazardous conditions range from tornadoes, large hail storms, and widespread straight-line winds called derechoes, to cloud-to-ground lightning and flash flooding.
Starting 2-Aug-2021, the National Weather Service will better convey the severity and potential impacts from thunderstorm winds and hail by adding a “damage threat” tag to Severe Thunderstorm Warnings, similar to their Tornado and Flash Flood Warnings.
“Destructive” and “Considerable” Damage Threat Categories
NWS developed 3 categories of damage threat for Severe Thunderstorm Warnings. The categories, in order of highest to lowest damage threat, are destructive, considerable, and base. These tags and additional messaging are designed to promote immediate action, based on the threats.
The criteria for a destructivedamage threat is at least 2.75 inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. Warnings with this tag will automatically activate a Wireless Emergency Alert (WEA) on smartphones within the warned area.
The criteria for a considerabledamage threat is at least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. This will not activate a WEA.
The criteria for a baseline or “base” severe thunderstorm warning remains unchanged, 1.00 inch (quarter-sized) hail and/or 58 mph thunderstorm winds. This will not activate a WEA. When no damage threat tag is present, damage is expected to be at the base level.
On average, only 10% of all severe thunderstorms reach the destructive category each year, nationwide. Most of these storms are damaging wind events such as derechoes and some of the larger, more intense thunderstorms, called “Supercell” storms that can typically produce very large hail in their path.
The new destructive thunderstorm category conveys to the public urgent action is needed, a life-threatening event is occurring and may cause substantial damage to property. Storms categorized as destructive will trigger a WEA to your cell phone.
Find some severe weather safety tips on weather.gov and download our free 60-page preparedness ebook plus some other safety tips at fedhealth.net
The National Weather Service launches it’s annual Hurricane Preparedness Week during the last week of Mayso we felt this was a good time to share some information about hurricanes in general.
The Seasons
As mentioned in our May 2013 enews, experts are predicting an active 2013 Atlantic season with 18 named storms, 9 hurricanes, and 4 major hurricanes. A typical Atlantic hurricane season averages 12 named storms, 6.5 hurricanes, and two major hurricanes (Category 3 or higher). Some experts are even predicting a few storms may strike the northeast (like Sandy did last fall) since conditions are similar to the 1950s.
According to the National Oceanic and Atmospheric Administration (NOAA), over a typical 2-year period, the U.S. coastline is struck by an average of 3 hurricanes, 1 of which is classified as a major hurricane. And, while hurricanes pose the greatest threat to life and property, tropical storms and depressions also can be devastating.
The Pacific Hurricane Season runs from May 15th through November 30th(with peak season being July to September), and the Atlantic Hurricane Season starts June 1st ending November 30th(with peak season being mid-August to late October).
However, there have been instances where tropical storms and hurricanes have formed in May and December, plus typhoons and cyclones happen during other months in different parts of the world so our planet’s oceans stay active most of the year.
Hurricanes are tropical cyclones with torrential rains and winds of 74 – 155 miles per hour (120 – 250 km/h) or faster. These winds blow in a counter-clockwise direction (or clockwise in the Southern Hemisphere) around a center “eye”. The “eye” is usually 20 to 30 miles (32 to 48 km) wide, and the storm may be spread out as far as 400 miles (640 km)!
As the hurricane approaches the coast, a huge dome of water (called a storm surge) will crash into the coastline.
Hurricanes can also cause tornadoes, heavy rains and flooding along the impacted coastlines as well as far into the mainland states.
Did you know…
…the deadliest hurricane (cyclone) on record struck East Pakistan (now Bangladesh), flooding the low lying areas?! At least 500,000 deaths are blamed on the November 13, 1970 storm, with some estimates rising as high as 1 million.
…the deadliest U.S. hurricane was the Great Galveston category 4 hurricane on September 8, 1900 that caused at least 8,000 deaths on the Texas coast?!
…the costliest U.S. hurricane was Katrina (category 3) in 2005 that impacted Alabama, Florida, Georgia, Louisiana, Mississippi and Tennessee causing over $105 billion according to NOAA?! Hurricane / Superstorm Sandy is second costliest at about $50 billion.
…the 2005 U.S. season broke records with 27 named storms (previous record was 21 in 1933) and 15 hurricanes (previous record was 12 in 1969). The National Hurricane Center states this cycle could last 10-20 more years similar to the above-average activity from the 1940s through the 1960s.
…9 out of 10 hurricane deaths are due to storm surge (a rise in the sea level caused by strong winds). Storm surges can get up to 20 feet (6 m) high and 50 to 100 miles (80 to 160 km) wide!
…the northeast part (or right front quadrant) of a hurricane typically has the strongest winds and highest storm surge?! If it’s high tide when the storm slams ashore you could have serious problems.
Hurricane basics
The ingredients for a hurricane include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds aloft. If the right conditions persist long enough, they can combine to produce the violent winds, incredible waves, torrential rains, and floods we associate with this phenomenon.
Each year, an average of 11 tropical storms develop over the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Many of these remain over the ocean and never impact the U.S. coastline. About six of these storms become hurricanes each year.
In an average 3-year period, roughly five hurricanes strike the US coastline, killing approximately 50 to 100 people anywhere from Texas to Maine. Of these, two are typically “major” or “intense” hurricanes (a category 3 or higher storm on the Saffir-Simpson Hurricane Scale).
Saffir-Simpson Hurricane Scale
Hurricanes are classed into five categories based on wind speeds, central pressure, and damage potential. The chart below is the Saffir-Simpson Hurricane Wind Scale with sustained wind speeds and examples of damage (in italics) provided by NOAA:
Category 1 (74-95 mph / 119-153 km/h) Dangerous winds will produce some damage (Untied mobile homes, vegetation & signs)
Category 2 (96-110 mph / 154-177 km/h ) Extremely dangerous winds / extensive damage (All mobile homes, roofs, small crafts, floods)
Category 4 (130-156 mph / 209-251 km/h) Catastrophic damage will occur (Roofs and mobile homes destroyed, trees down, beach homes flooded)
Category 5 (> 156 mph / >251 km/h) Catastrophic damage will occur (Most buildings and vegetation destroyed, major roads cut off, homes flooded)
Naming a hurricane
Since 1953, Atlantic tropical storms have been named from lists originated by the National Hurricane Center and now maintained and updated by an International committee of the World Meteorological Organization. The lists featured only women’s names until 1979, when men’s and women’s names were alternated. Six lists are used in rotation. Thus, the 2001 list will be used again in 2007. The only time there is a change in the list is if a storm is so deadly or costly that the future use of its name on a different storm would be inappropriate and the name is retired by the WMO. Retiring a name means it cannot be reused for at least 10 years. Source: WRAL.com
NatGeo vid “Hurricanes 101”
This short video further explains hurricanes, and scroll down to find more resources.
National Hurricane Preparedness Week 2013
As mentioned above, National Hurricane Preparedness Week 2013 runs from May 26 to June 1. The National Hurricane Center has posted 7 Public Service Announcements (both Youtube videos and audio files in English and Spanish) with a specific topic designated for each day of the week.
PSA topics include: Hurricane Basics, Storm Surge, Winds, Inland Flooding, Forecast Process, Get A Plan! and After the Storm. Learn more and find other resources and tools from NHC at www.hurricanes.gov to help educate your family and community.
Download a free 60-page ebook portion of our IT’S A DISASTER! book with tips on hurricanes, evacuations and more at fedhealth.net
By now you’ve probably heard Tropical Storm Isaac is churning in the Caribbean and may strengthen into a hurricane that could impact Florida and other Gulf coast states in the coming days.
Although 2012 has been a fairly quiet hurricane season so far, the Atlantic basin has seen 9 named storms, including 3 hurricanes, and the Pacific basin has seen 5 storms, 4 of which became hurricanes.
Keep in mind the storm season officially starts June 1 and runs through November 30, but August and September historically have been the peak activity months. For example, in 2010 and 2011, 12 named storms occurred in August and September both years. And it doesn’t take a hurricane to create havoc since tropical storms and depressions can bring torrential rains, tornadoes and flooding to coastlines and hundreds of miles inland.
Did you know…
…according to IBHS, more than half of the nation’s population now lives within 50 miles of the coast and the majority of properties there are exposed to the threat of hurricanes?!
…the 2005 U.S. season broke records with 27 named storms (previous record was 21 in 1933) and 15 hurricanes (previous record was 12 in 1969)?! The National Hurricane Center states this cycle could last 10-20 more years similar to the above-average activity from the 1940s through the 1960s.
…Hurricane Irene was the lone hurricane to hit the United States in 2011, and the first one to do so since Ike struck southeast Texas in 2008?!
…9 out of 10 hurricane deaths are due to storm surge (a rise in the sea level caused by strong winds). Storm surges can get up to 20 feet high and 50 to 100 miles wide!
Some things to think about and do to prepare for the storms…
Have a plan, map out several evacuation routes, and make disaster supplies kits for your home and vehicles. (And consider making kits for your office too.) And get some Weather radios with battery backup and tone-alert feature.
Make arrangements for pets since shelters may not allow them. If you have horses or livestock, make a plan for an alternate site in case they must be evacuated.
Videotape or take pictures of home and personal belongings and store chips/cards/drives with important papers in a secure, safe place offsite.
Consider getting flood insurance (and keep in mind it may take 30+ days to take effect). Learn more at www.floodsmart.gov
Strengthen weak spots on home — Roof: Install truss bracing or gable end bracing; anchors, clips and straps, etc. Windows & Doors: Get storm shutters or keep plywood on hand; install reinforced bolt kitsor doors, etc. Garage doors: Some retrofit kits install horizontal bracing onto each panel.
Secure / anchor mobile homes with tie-down systems.
Secure or tie down loose stuff like patio furniture, barbeque grills, water heaters, garbage cans, bookcases and shelving, etc. Loose items can become like missiles during high winds or tornadoes.
Keep materials on hand like sandbags, plywood, plastic sheeting, plastic garbage bags, lumber, shovels, work boots and gloves. Call your local emergency management agency to learn how to construct proper protective measures around your home.
Know where and how to shut off electricity, gas and water at main switches and valves — ask local utilities for instructions.
Listen to local authorities for warnings, evacuation tips and instructions, etc.
Download a FREE ebook portion of our IT’S A DISASTER! book with tips about Evacuations, Flooding, Hurricanes and more … and please share the information with others.
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