<P> Intense tropical cyclones pose a particular observation challenge, as they are a dangerous oceanic phenomenon, and weather stations, being relatively sparse, are rarely available on the site of the storm itself . In general, surface observations are available only if the storm is passing over an island or a coastal area, or if there is a nearby ship . Real - time measurements are usually taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength cannot be evaluated . For this reason, there are teams of meteorologists that move into the path of tropical cyclones to help evaluate their strength at the point of landfall . </P> <P> Tropical cyclones far from land are tracked by weather satellites capturing visible and infrared images from space, usually at half - hour to quarter - hour intervals . As a storm approaches land, it can be observed by land - based Doppler weather radar . Radar plays a crucial role around landfall by showing a storm's location and intensity every several minutes . </P> <P> In situ measurements, in real - time, can be taken by sending specially equipped reconnaissance flights into the cyclone . In the Atlantic basin, these flights are regularly flown by United States government hurricane hunters . The aircraft used are WC - 130 Hercules and WP - 3D Orions, both four - engine turboprop cargo aircraft . These aircraft fly directly into the cyclone and take direct and remote - sensing measurements . The aircraft also launch GPS dropsondes inside the cyclone . These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface . A new era in hurricane observation began when a remotely piloted Aerosonde, a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season . A similar mission was also completed successfully in the western Pacific Ocean . This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare . </P> <P> Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high - and low - pressure areas, and predicting how those areas will change during the life of a tropical system . The deep layer mean flow, or average wind through the depth of the troposphere, is considered the best tool in determining track direction and speed . If storms are significantly sheared, use of wind speed measurements at a lower altitude, such as at the 70 kPa pressure surface (3,000 metres or 9,800 feet above sea level) will produce better predictions . Tropical forecasters also consider smoothing out short - term wobbles of the storm as it allows them to determine a more accurate long - term trajectory . High - speed computers and sophisticated simulation software allow forecasters to produce computer models that predict tropical cyclone tracks based on the future position and strength of high - and low - pressure systems . Combining forecast models with increased understanding of the forces that act on tropical cyclones, as well as with a wealth of data from Earth - orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades . However, scientists are not as skillful at predicting the intensity of tropical cyclones . The lack of improvement in intensity forecasting is attributed to the complexity of tropical systems and an incomplete understanding of factors that affect their development . New tropical cyclone position and forecast information is available at least every twelve hours in the Southern Hemisphere and at least every six hours in the Northern Hemisphere from Regional Specialized Meteorological Centers and Tropical Cyclone Warning Centers . </P>

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