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Tropical storm Isaac moves into Gulf, hurricane warnings now in effect

Posted by David Epstein  August 26, 2012 11:30 PM

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As of this evening tropical storm Isaac was moving northwestward into the warm waters of the Gulf of Mexico. Once the storm is there, the conditions of the atmosphere and the water are ideal for significant strengthening of the storm. I am noticing on radar loops that the storm seems to be gathering strength. Isaac should become a hurricane as early as tomorrow but certainly by Tuesday. The ultimate landfall of the storm is still in question. Hurricane warnings are now in effect from Destin, Florida west to Morgan City, Louisiana. To illustrate how different the various computer models that track the storm are see the image below. Note one model has the storm going as far west as New Orleans while another is 300 miles to the east bringing the storm into the panhandle of Florida. Other models are in the middle. It is somewhat unusual to have this much uncertainty with a storm track when the hurricane (assume it will be) is going to hit an area in just a few days. Since the storm is moving into the Gulf region, I predict we will see energy prices skyrocket Monday and Tuesday as refineries and rigs get shut down. It was 7 years ago this week that Katrina took a similar path and that storm had a major affect on energy costs. For more frequent updates and analysis follow me on Twitter at @growingwisdom issacmodels.gif

New England weather
Before I write more about Isaac, let me briefly talk about our weather. The forecast for New England looks amazing through next weekend. The only exception to that forecast is a chance for showers Monday night and Tuesday with muggy conditions. Clouds will start to increase Monday but any showers will not occur until nighttime. Starting Wednesday there will be sunshine each day through Sunday. It will be in the upper 70s and lower 80s through midweek. Temperatures should turn quite warm (80s to 90F) later this week and to start next weekend.
Isaac track26.gif
Earlier today Isaac passed just about over Key West, Florida. The radar from that time shows bands of heavy rain and thunderstorms moving into the keys. Now the heaviest bands of rain are moving over the ocean. There can still be strong to severe thunderstorms and even weak tornadoes over parts of southern Florida overnight. radarkey.bmpFor the next day the track of Isaac is quite certain. However after tomorrow and into Tuesday major wobbles left or right of the track are still likely. The bigger question is what part of the Gulf Coast does Isaac ultimately strike late Tuesday night and early Wednesday. Anyone from New Orleans to Panama City Florida needs to be very aware of this storm until it makes landfall Tuesday night or Wednesday.

What is the cone of uncertainty?

The new buzz phrase seems to be the "cone of uncertainty". If you look at the projected track of the storm or the projected wind field you will notice these predictions start at a point and then widen into a "cone" shape over time. The further out in time a prediction is made, the greater the chance for error. The cone allows meteorologists wiggle room in their predictions and also gives the public a chance to know that even if the exact track is not over their area, there is still some risk. In the image below the darker colors represent those places that are most likely to see tropical storm force winds, the other colors are areas that those winds are possible, but less likely. Everyone in the cone should be listening to the latest forecast.
wind field Isaac.gif

How big will Isaac become?
Isaac is not well organized and is still a tropical storm. Now the storm is headed into an area of very warm water and more favorable conditions for strengthening. As a result, meteorologists are confident the storm will grow stronger tomorrow and Tuesday but uncertainty remains as to how strong the storm will become. Sometimes, if conditions are favorable, hurricanes can go from a Category 1 to a Category 3 in less than a day. Once the storm begins to get stronger tomorrow we will have to watch it hour by hour as it approaches the Gulf Coast.
cat 5 hurricane.bmp

Republican Convention and the storm
While the storm itself will have limited impact on Tampa and the RNC, the bigger issue I am thinking about is what happens Tuesday and Wednesday. I can foresee a scenario where the storm intensifies to a major hurricane, category 3 or higher and slams into the Gulf Coast. Imagine the visuals of homes destroyed and peoples lives ruined while the Republicans are having their convention. This could end up being a no-win public relations nightmare for the Republicans even thought the storm itself won't hit that part of Florida. Stay tuned.

Why do hurricanes form?
cyclone_map_thumb.en.gif
You might wonder why these storms form in the first place. I tell my students that hurricanes are nature's way of moving excess heat from the tropics to the northern latitudes. From about June through October, the oceans in the tropics are very warm. The water temperatures must be in the 80s not only at the surface but several feet below as well. This temperature structure to the sea only happens in the warm months. As the sun evaporates the ocean water that warm moist air rises and can, if conditions are favorable, create thunderstorms. In some cases, these clusters of thunderstorms will group together and begin to rotate. The rotation can be attributed to something called the Coriolis force. The Coriolis is strongest at the poles and zero at the equator. This is why hurricanes don't happen on or within several hundred miles of the equator. (no Coriolis=no spin) Winds inside the thunderstorms stir up more ocean spray which then evaporates and continues to feed the storms. If the winds reach 39 mph, the storm is called a "tropical storm." And when the wind speeds reach 74 mph, the storm is officially a "tropical cyclone," or hurricane. hurricane_needs_sm.gif Once the storm becomes a hurricane they are then categorized into 5 different levels of strength. Category 5 is the strongest and the last time one of those actually hit the United States was in 1992 when hurricane Andrew came ashore south of Miami.

Gardening tip this week

This is a great time of year to plant. I actually feel that for many plants fall is a better time to plant than it is in the spring. Since the ground stays warm well into October, roots have a good chance to become established. When you plant in the spring, much of the energy of the plant goes into making new leaves, not new roots.
If you have a tough spot that you can't seem to grow anything, check out this video and learn about some of the plants that actually thrive in hard to grow conditions.

I'd love to hear your thoughts on this blog or any others. Please follow me on Twitter at @growingwisdom and check out my latest videos at GrowingWisdom.com

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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About the author

David Epstein has been a professional meteorologist and horticulturalist for three decades. David spent 16 years at WCVB in Boston and currently freelances for WGME in Portland, ME. In 2006, More »
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