For 25 years, I have been fascinated by the power and unpredictability of weather. This feeling has been no more powerful than when it comes to tropical meteorology. Hurricanes are the most destructive storms our planet produces, with some systems being hundreds of miles across and causing tens of billions of dollars in damage. Despite extraordinary scientific progress in recent decades, it is fair to say that predicting both the track and intensity of tropical systems is still one of the hardest things to do in meteorology.
Last week was Hurricane Preparedness Week. This post seeks to provide an overview of how tropical systems develop, some of the tools we have to track and forecast them, and what hurricane season means for Connecticut. I will also share some of the key points to help you prepare for the season. Grab a drink, sit back, and enjoy the post.
What is a Hurricane?
First, let's start of the basics. Everything posted is focused exclusively on our part of the world. Tropical systems are different from our usual fall or winter coastal storms in that they exclusively receive their energy from the warm waters of the tropical and subtropical regions of the Atlantic Ocean. These are organized systems of thunderstorms (convection) that have a closed low level center of circulation. There are multiple levels of tropical systems.
- Invest: An invest (95L as an example) is an area of interest. It is not an official tropical system that would bring frequent official updates from the National Hurricane Center (NHC). An invest is often a tropical wave that has the potential to develop. Having an invest designation means that more tracking and forecasting resources are used to determine the future of the area of interest.
- Tropical Depression: A tropical depression is an official tropical system or cyclone. For a tropical depression to be classified, there must be consistent convection and a defined low level center.
- Tropical Storm: A tropical storm is a system with maximum sustained winds of 39 to 73 mph (34 to 63 knots).
- Hurricane: A hurricane is a system with maximum sustained winds of 74mph and above (64 knots). A major hurricane is a category three or higher system (111mph and above).
It is important to note that maximum winds do not need to be found in all areas of a tropical storm or hurricane to warrant the classification. In fact, often times you find the highest winds in the northeast quadrant of a tropical system.
Hurricane season lasts from June 1st to November 30th, but the overwhelming majority of the season takes place between late August and early October, with the climatological (or historical) peak of the season being in early/mid September.
Tools in the Toolbox
There are a plethora of tools that forecasters use to predict tropical cyclone genesis and future track and intensity.
- Satellite: Satellites such as GOES-16 are incredibly helpful tools in helping forecasters identify areas of interest, upper level features that determine the future track of systems, and the growth of hurricanes.
- Radar: Just as it is helpful for severe weather and rain, radar is a vital tool in helping us understand the inner core of tropical systems. It is also critical in identifying tornadoes that are quickly spun up by landfalling tropical systems.
- Computer Models: The guidance, both ensembles (think GFS ensembles and Euro ensembles) and deterministic (think GFS, Euro) are critical tools as they analyze virtually every aspect that impacts track and intensity of tropical systems. One important tool now is the HWRF model, which is the best intensity model we have currently. An important note here however is that the HWRF is at its best when there is an actual organized center of circulation.
- Hurricane Hunters: While the computer models are critical, they are only as good as the data they have. This is where the king of our forecasting tools comes into play. The Hurricane Hunters fly into tropical systems and gather vital data on the strength and intensity trends of systems, and other planes fly around the system to help us get a better handle on the upper level pattern that eventually steer the system. A tropical system is not a bull in a china shop. It is a leaf floating in a river. Tropical systems are driven by the environment around them.
In this decade, New England has seen two tropical related events that have devastated large swaths of the region, but neither were hurricanes when they impacted the region. The last landfalling hurricane was Hurricane Bob, which hit New England in 1991.
Overall, according to data that goes back to 1851, the averages show that while hurricane strikes are infrequent, they do happen. Again, this does not even include tropical storm landfalls or indirect strikes such as Irene and Sandy, which did extraordinary damage to parts of New England and Connecticut.
Hurricane Landfalls: Once every 10 years
Major Hurricane Landfalls: Once every 56 years
As mentioned above, our last hurricane landfall was in 1991 with Hurricane Bob. It did not make a landfall in Connecticut, but there were significant impacts in the state.
The last major hurricane landfall was in 1954, perhaps our most active year in the historical record with Major Hurricane Carol and Hurricane Edna (which was originally a major hurricane before reanalysis moving it to category two) making landfall, along with the strong winds that came with the remnants of Hurricane Hazel.
In 1955, the remnants of major hurricanes Connie and Dianne (which was a tropical storm on closest approach) created one of the great floods in Connecticut's history. These two storms hit nearly a week apart, and 87 people were killed along with thousands of structures destroyed.
Below, part one of a 1956 special on the Great Flood.
Although New England has far fewer threats from landfalling hurricanes, Connecticut with its central location, is nonetheless prone to landfalling tropical systems. For our region, tropical landfalls are usually made by rapidly moving systems that are moving north or northeast along the periphery of an Atlantic area of high pressure and/or along a trough that pushes in from the west and pulls a system northward rather than kicking it out to sea as it does the overwhelming majority of the time. Even with today's technology, the final track of many tropical systems that threaten the US are not known until a few days in advance.
As you can see above, even without a direct landfall from a tropical system, Connecticut can experience significant impacts from tropical remnants and systems that pass to our west or east. When dealing with tropical systems, it is always important to remember that the center is not the only place where damaging weather can occur.
Most people think of wind when it comes to tropical systems. Even "weak" category one hurricanes or tropical systems can cause significant wind damage to trees and power lines. Just think of the damage Sandy did while the center made landfall hundreds of miles to our southwest. Sandy had the largest wind field on record in this region.
The key hazard in a tropical system is often flooding. In fact, most deaths in tropical systems are due to flooding that is caused by either excessive rainfall or storm surge. The Connecticut coastline remains vulnerable to storm surge, and all of Connecticut is at risk of flooding due to heavy rainfall from a tropical system that makes a close enough approach.
Tropical systems can be prolific producers of tornadoes, particularly on the right side of the storm. These can happen anywhere and although they are generally on the lower end of the Enhanced Fujita scale, they can still do significant damage to property and communities.
Rip currents are also another important hazard that isn't frequently mentioned. Rip currents can occur hundreds of miles away from a tropical system.
Hurricane Season Preparation
It only takes one storm to change your life. No matter if you are in Groton or Hartford, it is important to remain weather aware during hurricane season--especially during the peak--and be prepared in case a tropical system or its remnants sets its sights on us.
- Determine Your Risk: Whether you are inland or at the shoreline, now is the time to determine your risk level. Are you in an area that experiences large waves during storms? Are you in an area that loses power easily? Are you in an area that floods a lot during rain storms? Do you have flood insurance? Asking these simple questions now can prepare you for later.
- Develop an Evacuation Plan: For those along the shoreline, know your flood and evacuation zone. Know what it takes for the call to be issued, know if your home can withstand a hurricane in particular, and if you are ordered to evacuate, do so. Plan your route to safer ground and plan for your pets. Remember, it does not take a major hurricane to cause major flooding and storm surge.
- Assemble Supplies: As we have learned from recent tropical and winter storms, you need to have supplies in case we experience large systemic power outages. Consult local emergency manager sites and FEMA to plan ahead.
- Get an Insurance Check Up: Standard homeowner insurance does not typically cover flooding, which is the greatest hazard in most tropical systems. Make sure you have the appropriate amount of rental or homeowner insurance. Right before a storm, or worse, right after, is not the time to find out you're not covered.
- Strengthen Your Home: Securing outdoor items, trimming limbs, and moving your car to a safe location are all important things to think about if a storm is bearing down on Connecticut. If you are at home during a storm, put yourself and your property in a position to make it through an event unharmed.
- Help Your Neighbor: Recent disasters have taught us that often times the community must band together after an event. Don't be afraid to talk about storm preparedness with your neighbors and collaborate on planning. A bad tree or unsecured items in your neighbors yard can do very real damage in yours.
- Complete a Written Plan: Write things down! Having a written plan ensures that you don't have to start from scratch when a storm is coming, and helps to reduce anxiety that many feel before a potential natural disaster. A written plan ensures that you are prepared for whatever happens, and keeps you and your family safe.
The last hurricane to make landfall in Connecticut was Hurricane Gloria in 1985. An entire generation of residents have lived in the state without a direct hurricane hit.
Some day, this period of relative calm will end.
SCW will be there to provide you with information from official sources and our own thoughts should anything pose a threat to Connecticut.
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Thank you for reading SCW.