Hurricane Facts

For a tropical cyclone to form, you need to have two main characteristics in place.

1. There needs to be warm waters in place. If the water temperatures are below the mid 70's F, there will probably not be any tropical development. In order for a hurricane to form, you need the water temperature to be about 80 degrees F or above. Intense hurricanes usually form when the water temperatures reach about 85 degrees F or above. They do not always follow this scale because of other atmospheric events, but generally the Atlantic, Caribbean, and Gulf follow these patterns.

2. Winds aloft have to be light. This is a very hard factor to understand, because this is opposite of land based storms. Storms on land need the vertical wind sheer to maintain their intensity. However, hurricanes seem to work backwards. When there is a lot of vertical wind sheer over a hurricane, they weaken and fall apart. It is a bit more complicated to know the upper-level winds over the ocean than it is on land, but with new age technology and ship stations out in the ocean, we get enough surface and upper air conditions and forecasts to make good predictions. Hurricanes develop the most rapidly when there is an area of high pressure aloft located directly over the center of the low-level circulation. Since the core of the high pressure has calm winds, this prevents any vertical sheer from occurring which in turn adds more fuel to the fire for the hurricane.

OBTAINING CURRENT CONDITIONS ON A HURRICANE.

The National Hurricane Center in Florida issues advisories on tropical systems. Tropical weather outlooks and discussions are issued every 6 hours. Advisories on named storms are also issued every 6 hours for the most part. When a storm threatens land, intermediate advisories are posted every 3 hours and sometimes every 2 hours. In order for the Hurricane Center to issue advisories on the storms, they must know the exact position of the storm as well as the winds, pressure, direction, etc…There are several ways used to obtain this information.

• Hurricane Hunter aircraft can be sent directly to the location over the ocean to give flight-level winds and information. From there formulas can be worked out to give a good estimation of surface conditions, or either a dropsonde can be sent down into the eye. A dropsonde is an instrument containing weather equipment that is dropped by the planes into the center of circulation to obtain surface conditions.

• Buoy or ship reports are very important in tracking conditions of a tropical cyclone. These are ships that are either drifting or mounted in the ocean that are equipped with weather instruments.

• Satellite pictures are used a lot in tracking tropical systems too. While they aren't quite as accurate as the first hand aircraft or ship report information, they still give a good estimation of the storms and you can generally tell when one is strengthening.

• Once a storm gets near land, it is then tracked with land-based Doppler Radar. The eye or center of circulation appears very evident on the radar and you can see the position live as it moves onshore. Below is an image of a doppler radar taken during an approaching hurricane.

If you are wanting to know how far a hurricane out in the ocean is from your area, then you would use the "Great Circle Distance" formula. This formula takes the latitude and longitude of your area and of the hurricane to give the distance between the two points on the Earth. Since the Earth is a sphere and not flatly round, things get a bit complicated. The formula has to measure the distance from your location to the definite center of the Earth underground. This will form an imaginary line. Now you do the same from the hurricane to the center of the Earth underground. You now have two imaginary lines that meet at a vertex at the center of the Earth and end at separate points on the Earths surface "your house and the hurricane". Once the formula figures the distance of those two imaginary lines, it uses those distances to measure the distance between the two points on the unlevel surface of the earth. It's all similar to the pathagorean theorm that almost everyone is familiar with "keyword is similar, because this doesn't create a right triangle because the surface of Earth is a sphere and not flat and level." The pathagorean theorm is simply (A^2 + B^2 = C^2)...If you know two sides of the triangle, you can figure out the third side. Drawing an imaginary line from your house to the center of the Earth, then from the center of the earth to the hurricane, then along the surface of the Earth back to your house "kinda" makes a triangular shape. So if you know side A "from your house to the center of Earth" and you know side B "from the hurricane to the center of Earth", (which the great circle distance formula figures out for you, all you have to know is latitude/longitude), then you can figure out side C "the distance from the hurricane to your house." Of course, a formula like this will go into a little bit of trigonometry, but if you use the calculator or enter it into a spread sheet, it's really quite simple. The great circle distance formula is as follows:

HOW TO PREPARE FOR A HURRICANE.

Hurricane Watch: Hurricane conditions are possible within 24 to 36 hours.

What should you do?

• You might want to stock up on supplies such as bread, batteries, and bottled water in the event of possible power outages.

• Have emergency numbers located where you could easily get to if needed.

• Plan on where you would go if an evacuation was necessary.

• Remove loose objects in your yard such as trash and lawn chairs.

Hurricane Warning: Hurricane conditions are expected within 24 hours. Take quick action to protect life and property!

What should you do?

• Evacuate if told to do so or if you feel unsafe being at the place you are when the storm hits. Once the storm has started, it is too late to evacuate!

• Board up and tape windows to prevent them from breaking, or widespread glass if they do break.

• Listen to TV and radio stations for the latest information.

HURRICANE PICTURES

The following pictures are of Hurricane Mitch over the Caribbean Sea as a category 5 hurricane. The first is a visible satellite, a camera recording from outer space and the second is an infered satellite, which indicated convection. The darker colors mean heavier convection which means stronger storms.