Hurricane Preparedness Week 2023: understand forecast information

It’s Hurricane Preparedness Week here on CBS 12 News. Each day the CBS 12 StormTrac Weather Team will cover ways you can prepare your home and family for the upcoming season.

Tuesday's topic is understanding forecast information.

How do hurricanes form?

Tropical systems start out as tropical waves. Ahead of the wave, there will be fair weather and calm winds. Behind the waves, there will be storms and stronger winds. If conditions are right, the storms along the wave will organize and develop an area of rotation. Some of these areas will develop a closed center of circulation and strengthen into a tropical depression, storm, or eventually a hurricane.

What’s the difference between a tropical depression, a tropical storm, and a hurricane?

Tropical Depressions are storms that have a close center of circulation and produce sustained winds of 35-38 mph. Tropical Depressions will never have a name, but will instead be given a number, for example, Tropical Depression One or Two.

Tropical Storms are storms that have a close center of circulation and produce sustained winds of 39-73 mph. Storms will get names and will follow the naming list that has been released for this year. If the list of names is exhausted throughout the season, we move on to the Greek Alphabet. Once a storm is named, it will retain that name for its lifecycle, meaning if it gets downgraded to a Tropical Depression, it will keep its name despite the downgrade to depression status.

Hurricanes are rated from Category 1 to Category 5. The winds increase with each category. The sustained wind speeds for each category are:

• Category 1 hurricane: 74-95 mph.
• Category 2 hurricane: 96-110 mph.
• Category 3 hurricane: 111-129 mph.
• Category 4 hurricane: 130-156 mph.
• Category 5 hurricane: 156+ mph.

A major hurricane is category 3 strength or higher and can be extremely dangerous to life and property, but it doesn’t take a major hurricane to produce significant impacts.

Rely on the forecast issued by the National Hurricane Center. Meteorologists at CBS 12 will relay official forecasts from the NHC.

The NHC will issue Tropical Weather Outlooks every day during the season. Since 2015, the NHC has issued a two-day and five-day tropical weather outlook during the season. These outlooks are different from the official forecast cones and are used to identify areas that are favorable for potential tropical formation. TWOs are presented with a color-coded scale; yellow indicates a low chance of development, orange indicates a medium chance, and red indicates a high chance of development.

The NHC will expand the TWO, introducing a seven-day outlook for the 2023 hurricane season. The NHC will no longer release a five-day outlook. Instead, the outlooks will now cover a two and seven-day time that highlights areas in the Atlantic, Caribbean, and Gulf of Mexico that may produce a storm.

The most important product issued by the National Hurricane Center is the official forecast cone. This cone is also called the “cone of uncertainty,” because the forecast uncertainty is conveyed by the cone’s shape.

The cone represents the probable track of the center of a tropical cyclone. Based on forecasts over the previous 5 years, the entire track of the tropical cyclone can be expected to remain within the cone roughly 60-70% of the time. A storm may not follow through the exact center of the cone and impacts can be felt hundreds of miles away from the middle of the storm.

The National Hurricane Center will also issue graphics that show the arrival times of Tropical Storm Force Winds. This forecast shows when sustained winds could at the earliest reach 40 mph or make it dangerous to be outside doing anything. This includes last-minute preparedness activities. Winds of this intensity and higher gusts can cause damage to structures and can overturn and/or move some objects like ladders and plywood.

Know your alerts and the difference between a watch and a warning.

If our area is threatened by a tropical system this season, you’ll hear about a variety of different watches and warnings that will be issued. They might include:

• Tropical Storm Watch — Sustained winds of 39-73 mph are possible in the next 48 hours. You should begin preparations now.

• Tropical Storm Warning — Sustained winds of 39-73 mph are expected within the next 36 hours. Complete your storm preparations now and get ready to take shelter.

• Hurricane Watch — Hurricane conditions with sustained winds of 74 mph or higher are possible within the next 48 hours. Begin preparations now.

• Hurricane Warning — Hurricane conditions with sustained winds of 74 mph or higher are expected within the next 36 hours. Finish preparations now and seek shelter.

• A Storm Surge Watch — is the possibility of life-threatening inundation generally within 48 hours, and a Storm Surge Warning means the danger of life-threatening inundation generally within 36 hours. In either case, please promptly follow evacuation and other instructions from local officials.

• An Extreme Wind Warning — extreme hurricane winds (115 mph+) are imminent or happening: take immediate shelter in an interior portion of a well-built structure.

• A Flash Flood Warning — dangerous flash flooding is expected: move to higher ground, and never walk or drive through floodwater. A Flash Flood Emergency is issued for exceedingly rare situations when a severe threat to human life and catastrophic damage is happening or about to happen — do NOT attempt to travel unless you are under an evacuation order, or your life is imminently at risk.

• A Flood Watch — flooding is possible: stay tuned to trusted news sources and be ready to seek higher ground. A Flood Warning means flooding is happening or about to happen move to higher ground immediately.

• A Tornado Watch — a tornado is possible: know your safe place and be ready to act quickly if a Warning is issued.

• A Tornado Warning — means a tornado is happening or about to happen - immediately seek shelter in your safe place!

Focus on potential impacts, regarding the storm size or category.

Do not focus on a storm's category as all tropical storms and hurricanes can bring the threat of storm surge, inland flooding, and damaging winds. The saffir-simpson scale only tells you about the maximum wind speed near the center of the storm and doesn't tell you about impacts well outside of a storm. Remain vigilant even if the storm becomes a lower category or tropical storm or depression as rainfall and storm surge impacts can still linger.

• Category 1: hurricanes can produce minimal damage. Some shingle and gutter damage is possible. Vinyl siding may blow off a few houses. Expect several large branches to snap and some small trees to topple over.
• Category 2: hurricanes can produce minor damage, mainly to siding and roofs. Expect several homes with shingle damage, but well-built houses should remain largely undamaged. Many trees are expected to be snapped and uprooted.
• Category 3: hurricanes can produce moderate damage, including major damage to mobile and manufactured homes. Well-built homes can expect moderate damage to roofs, including shingles ripped off. Several windows can be blown out.
• Category 4: hurricanes can produce major damage to neighborhoods across South Florida. Several homes with complete damage to roofs and windows. Some homes, including most mobile and manufactured homes, are destroyed.
• Category 5: hurricanes can produce catastrophic damage to the region. Extensive home damage, with several well-built homes destroyed. Mobile and manufactured homes were left unrecognizable.

Know that deadly hazards can occur well outside of the forecast cone. Impacts can be felt far from the storm's center, even well inland and outside the forecast cone. Even tropical storm force winds can cause damage, toss around debris, and take down powerlines.