Hurricane Isaac has made landfall in Louisiana's Plaquemines Parish this evening and the storm will continue to move slowly along the coast over the next day. There has been 106-mph wind gust recorded on an rig in the Gulf. Storm surges up to 8 feet have been seen in the area and worse is likely to occur overnight and into Wednesday. The biggest issue with this storm is going to be the slow movement and the large amounts of rain that will fall as a result. Some places will see over a foot of rain between now and Thursday morning. The two images below show the clouds and the rain associated with Isaac. Notice on the radar how clearly the eye is visible. That is the the area in the middle that looks like a donut hole.
Damage so far
Over the past few days there was some serious flooding in Florida. Very few in the national news are talking about the flooding across that State. Some towns are under water, roads were washed out and people were stranded. Canoes had to be used by folks around the Lake Worth area of Palm Beach County to get around. The flooding will be receding overnight, but is certainly a sign of what is to come in and around New Orleans over the next two days.
Current track and projections
Now that the storm has made landfall it will hug the coast and very slowly move inland during Wednesday. Some areas may see tropical storm force winds and rain for 12 or even 18 hours. Normally, storms move faster than Isaac once they hit land. The slow movement of this storm is going to make this worse than a typical category one storm, if there is such a thing in the first place.
How much rain?
Rainfall will be close to a foot northwest of the eye's landfall. You can see on the image below that there is little rainfall in the eye, (center) but increasing amounts of rainfall predicted away from the eye. They key to how much rain falls is on the right side of the image. The storm is forecast to move very slowly and this will allow the rain to fall for a longer period of time. Flooding is certainly going to be an issue in many areas in the path of this storm.
The remnants of the storm will eventually move into drought stricken areas of the Midwest. This is good news for farmers who might be able to save some of their fall crop but unfortunately will be too late for most. However, just begining to end the drought across the center of the Country is a good thing. Winter wheat and other crops will do better if planted in moist soil.
Damage from the storm
Tropical storms and minimal hurricanes can cause a tremendous amount damage. Vermont saw some of its worst flooding in a century from tropical storm Irene. It's impossible to predict how much damage this storm will cause. The good news is that billions of dollars have been spent to upgrade the levee system in New Orleans. This won't be a major test of that system, but a test nonetheless.
Why do hurricanes form?
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. 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.
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