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Tropical Storms and Aerosol Transfer Affecting Inland Weather

The Troposphere, the lowest level of the atmosphere reaches an altitude of about 10,000 feet (3048 meters) in the mid latitudes, and is the source region for all of the intense weather experienced on earth. Every year there are dozens of Hurricanes, Tropical Storms and hundreds of Tropical Depressions. The Atlantic is a one major source region for these intense weather producing systems.

Hurricanes
Hurricanse are determined by average wind speed and barometric pressure. The lower the barometric pressure the more intense the Hurricane becomes. Typically Hurricanes form between 5 and 20 degrees latitude. Near the tropics convection is intense from surface heating, and winds are light. Air with high moisture content rises upward and the water condenses into visible forms of clouds releasing latent heat. The air cools and falls as the heat is released. A low pressure zone is created and if cyclonic winds are present (counterclockwise in the northern hemisphere) and a Tropical Storm may develop. Warm sea water is the common source of moisture. Hurricanes may produce high winds in excess of 120 mph (260kilometers per hour). Even Tropical Storms may produce winds up to 74mph (119 kph). While an average of five hurricanes develop in the Atlantic Ocean every year, with two of them being major (Category 3 or greater), Tropical Storms are even more numerous. 2005 was an extremely active year for Atlantic storms. In all there were 27 named storms with 14 becoming mature hurricanes. This was the largest number of hurricanes on record for a single season. Eight of these were major hurricanes. Katrina is particularly remembered in the United States.

Hurricanes and Tropical Storms, after making landfall may be downgraded to or remain in a Tropical Storm Status for a time but will, subsequent to making landfall often become a lesser intensity Tropical Depression. The large amount of water vapor contained in these storms combined with lower latitude warm air, intense convection and other influences such as the Jet Stream often combine to produce weather which will traverse the country for days after such a powerful weather system reaches land.

Storms reaching the south-central coasts of North America, moving inland after making landfall on the coasts of Mexico or Texas for instance, often vector northward, spreading over thousands of square miles / kilometers. Commonly water filled air masses are moved northward by the jet stream toward cooler air moving eastward from the Rockies. The result is commonly large areas of cloud and often intense thunderstorms or isolated low pressure systems.

Aerosols as a Modifying Factor of Inland Weather
One of the many modifying factors for inland weather produced by these warm, wet air masses which originate in a low latitude storm’s arrival at land is the solid aerosols which the tropical low pressure system sweeps up and moves with it by means of intense winds. Geospatial Data for 2010 indicates that for Hurricane Alex and Tropical Storm  Hermine making landfall in Mexico and Texas, the winds on the edge of the storms may have transferred tons of otherwise static aerosols into the air and moved them inland with the help of the jet stream. These aerosols, some organic and some man-made (such as mining or construction fines) are a key factor in the production of further intense storms inland. The microphysics of clouds are complex, but the propagation of thunderstorms and other weather altering systems  inland after the arrival of a Hurricane or Tropical Storm, are often intensified and multiplied due to the large influx of microscopic aerosols placed in the troposphere by high winds from the storms.

Small particles (aerosols) which may range from .05 micrometers (um) to as large as 70-80 um in size of particulate matter (PM 70-80) are, what water vapor (WV) molecules cling to when the particulates are present in the atmosphere. These particulates might be dust, salts from ocean air, or any other superfine particle. Even at altitudes above the Troposphere, where the air may be as cold as -100 degrees F ( -73 C ) water vapor will remain in its state until the WV molecules come into contact with suspended fine solids (condensation nuclei) such as soot from jet engines for example. In the upper reaches of the atmosphere, the supercooled water vapor will instantly freeze or condense onto the condensation nuclei and form the beginnings of clouds. With the addition of a large amount of aerosols added to the troposphere by arriving low-latitude storms such as Alex or Hermine, the potential for long lasting, multiple weather systems inland increases based on the area of landfall by a major storm as well as the intensity of its winds. Many different types and levels of clouds are a net result of Hurricanes or Tropical Storms vacuuming the aerosols into the Troposphere when making land, thus changing local or regional weather to varying degrees inland. NOAA wind maps show an example of upper level winds and their tracking influence on storms. After making landfall, Hurricane Alex is shown on July 3, 2010 adding moisture to the interior of the country carried by upper level winds. Surface winds as well as upper level winds upon landfall of the storm pick up very small fines in the form of particulates and move them in the the weather stream. See wind example: