Thursday, July 24, 2014

Tropical Thoughts

Track of Hurricane Arthur
We are well into the tropical storm season, and things in the Atlantic have been very quiet so far. The only activity was Hurricane Arthur at the beginning of the month and a recent tropical depression that quickly dissipated. The eastern Pacific has been a little more active with two hurricanes and three tropical storms. NOAA's 2014 Atlantic Hurricane Season Outlook calls for a near-normal to below normal season, with an expected 8-13 names storms, 3-6 hurricanes, and 1-2 major hurricanes. The normal range is 12 named storms, 6 hurricanes, and 3 major hurricanes.


Of course, the outlook says nothing about land-falling storms, and coastal residents know that it just takes one storm to wreak havoc in an area, and it doesn't have to come ashore. Arthur was a good example of that. We are still several weeks away from the peak of the season so the lack of activity should not lead anyone to complacency. While the tropics are quiet, however, it's a good time to become familiar with a couple of new experimental products that have been introduced by the National Hurricane Center.

The first of these is a new 5-day Graphical Tropical Weather Outlook. This outlook indicates the formation potential of current and future disturbances during the next five days. Shaded areas will represent the potential tropical cyclone formation areas, similar to the current 2-day outlook. Yellow represents a low chance (<30 percent), orange a medium chance (30 to 50 percent), and red a high chance (> 50 percent) of tropical cyclone in the next five days.

You can view a video about the outlook at here.

The second product is a potential storm surge flooding map. This map product has been in development for several years and is designed to clearly depict the risk from storm surge by show the areas where flooding from storm surge could occur and how high above ground the water could reach. Flooding from storm surge accounts for about half the deaths associated with tropical cyclones, and many people do not understand the threat from storm surge. Four colors will represent flood levels from up to 3 feet, greater than 3 feet, greater than 6 feet, and greater than 9 feet. The map is produced using forecast and statistical models, and accounts for flooding from storm surge from the ocean, astronomical tides, land elevation, and uncertainties related to the forecast of the cyclone. It does not account for flooding from heavy rain, wave action, or overtopping or failure of levees. The maps can change as the storm track and intensity forecast changes.

Here is a sample map of flooding along the Texas Gulf Coast.

Experimental potential storm surge flooding map for a sample hurricane along the Texas Gulf Coast.

You can view a short video about the experiment storm surge map here.

The National Hurricane Center is accepting comments and feedback about both of these products, and you can find the feedback forms on the page describing the product

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