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Forecasting the storm

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Posted: May 29, 2014 11:01 AM by Meteorologist Josh Eachus
Updated: May 29, 2014 11:01 AM
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Topics: weather, forecasting, tropical, hurricanes, preparedness

Different from your daily 7-day forecast and futurecast rain chances, the National Hurricane Center issues several probability-based graphics. This is done to provide insight and assist in decision making for those possibly affected by inherently erratic tropical cyclones.

The first product you will see, prior to the development of a storm, is the tropical weather outlook. It highlights areas of disturbed weather in the tropics and displays the probability a storm complex has of developing into a tropical depression.

Once a tropical cyclone has been identified, forecasters evaluate the state of the atmosphere and analyze computer models to project the storm's movement. Sometimes you will see the "spaghetti-plots" which show a number of possible storm paths, all generated by a different computer model. The National Hurricane Center will smooth out these differing plots into a forecast cone. The cone accounts for forecast errors and additional uncertainty. On average, the center of the tropical cyclone will remain inside of the cone 60-70% of the time. Always remember that the cone forecasts the path of the storm's center and tropical cyclone effects may still be felt well outside of the cone.

Should a storm approach land, tropical storm and hurricane watches and warnings may be issued. Coastal locations will feature a colored outline on the map. Hurricane warnings are crimson and hurricane watches are magenta. Tropical storm warnings are brick red and tropical storm watches are a coral pink. In a major hurricane, extreme wind warnings may be issued and colored dark orange. Rare, these warnings are for areas expected to be impacted by the eye-wall of a hurricane with winds exceeding 115mph.

When a storm is forecast to make landfall, a wind speed probability map will be issued. Hashed out, colored areas will denote the chances of tropical storm force and hurricane force winds for a given area. The product accounts for the track, peak winds and size of the storm. This graphic accounts for the fact that tropical cyclone effects can be felt well away from the "forecast cone" and the storm's center of circulation.

New this year, the National Hurricane Center will be issuing a storm surge probability map similar to the wind probability map. Hashed out, colored areas will convey the percent chance of surge exceeding various thresholds for a given area.

WBRZ.com will keep you updated, featuring additional information about tropical cyclones through Hurricane Preparedness Week. You can get much more by also visiting www.nhc.noaa.gov/prepare/

Remember to check out our special, "Weathering the Storm," airing on WBRZ Sunday, June 1st from 6 - 7pm.

You can get forecasts from Meteorologist Josh Eachus weekdays on 2une-In from 5-7am and News 2 at Noon from 12-1pm. Additionally, you can get the fastest and latest forecasts and weather news by checking in with wbrz.com/weather, liking Josh on Facebook and following him on Twitter.

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