Information is again in the classroom.
Sixth Grade Science...Weather...It is hurricane season. Keep an eye on what is happening. Remember New Orleans ten years after Katrina? Slow recovery if at all.
Question: What was the largest hurricane in United States history?
The Huffington Post reported in a post on October 29, 2012 that Sandy, a category 1, was the largest hurricane at 1000 miles in diameter in the United States since 1851 according to the National Hurricane Center. In contrast Hurricane Katrina in 2005 a category three storm was 415 miles across. Sandy also became know as "Frankenstorm" as it is estimated to have caused 20 billion dollars ($20,000,000,000) in damage along the northeast coast.
This map is from NOAA's SciJinks web site.
From "spaceplace.nasa.gov/hurricanes/en/ we find that hurricanes only form over warm ocean water near the Earth's equator. Looking at the above map you can see the different names for these powerful storms at locations around the planet. In these ocean warm moist waters near the surface of the water move upward. As this air moves upward into the atmosphere, a lower pressure area forms above the water's surface. The surrounding area of air has a higher pressure and new air swirls into the lower pressure area. This new air is then heated and moisturized and it too rises up as new cooler air rushes in. This process will continue. As the moisture ladened air rises into the cooler atmosphere, clouds will form. This system of clouds and wind continue to get larger and more powerful being fed by the warm waters of the ocean.
(spaceplace.nasa.gov/hurricanes/en/)
If you could slice into a tropical cyclone, it would look something like this. The small red arrows show warm, moist air rising from the ocean's surface, and forming clouds in bands around the eye. The blue arrows show how cool, dry air sinks in the eye and between the bands of clouds. The large red arrows show the rotation of the rising bands of clouds.
When winds in the storm reach 39 miles per hour, it is labelled as a tropical storm. When the sustained winds are 74 miles per hour it is now a hurricane/cyclone.
As in Sandy, the hurricane's storm surge can cause much damage as water surges inland along coasts of landforms. Being that Sandy was so large, its storm surge just kept coming inland along the coast wiping out parts of coastal towns. Here is a list of storm surge heights of different categories:
(spaceplace.nasa.gov provided this information)
Category wind speed (mph) storm surge
1 74-95 4 to 5 feet
2 96-110 6 to 8 feet
3 111-130 9 to 12 feet (Katrina: 25-28 feet)
4 131-155 13 to 18 feet
5 over 155 19 plus feet
I wanted to know how fast a storm surge would move inland so I went to www.nhc.noaa.gov/surge and this is what I learned. The height of a storm surge can be affected by how the width and slope of the continental shelf. A slow gentle up slope of the continental shelf would create a higher storm surge than if the continental shelf was short and steep. Also if the storm surge, driven by the storm's high winds, enters into a waterway that narrows into a bay or cove the surge will be higher. The timing of high and low ocean tides will affect the heights of the storm surge. Why then does the storm surge wave "piles up"? It is the result of the up-slope of the continental shelf and the slowing of the front edge of the wave due to friction of the water with the continental shelf.
Wind and Pressure Components of Hurricane Storm Surge
The maximum potential storm surge for a particular location depends on a number of different factors. Storm surge is a very complex phenomenon because it is sensitive to the slightest changes in storm intensity, forward speed, size (radius of maximum winds-RMW), angle of approach to the coast, central pressure (minimal contribution in comparison to the wind), and the shape and characteristics of coastal features such as bays and estuaries.
To learn more you have got to go to: www.nhc.noaa.gov/surge.
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