Question: Tropical Storm Marco was the only tropical cyclone to make landfall on the United States during the 1990 Atlantic hurricane season, the cyclone combined with a cold front, to produce heavy rainfall in Georgia and the Carolinas, with the remnants of Hurricane Klaus, a minimal Atlantic hurricane that dropped heavy rainfall across the Lesser Antilles in October of which year?

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Tropical Storm Rachel (1990): Tropical Storm Rachel was the only tropical cyclone to make landfall during the 1990 Pacific hurricane season.  The twenty-fourth tropical depression and eighteenth named storm, Rachel developed on September 27 from a tropical wave southwest of mainland Mexico.  After becoming a tropical depression, the system tracked slowly southwestward and eventually curved northwestward.  The depression intensified into a tropical storm after three days and was named "Rachel" by the National Hurricane Center.  Rachel continued to steadily strengthen, and peaked as a strong 65 mph (100 km/h) tropical storm on October 2.  After attaining peak intensity, Rachel re-curved to make a landfall in southern Baja California Sur and again in the Mexican Mainland on October 3.  The storm produced heavy rainfall across northern Mexico and the Southwestern United States.  Thousands of people were left homeless and 18 fatalities were reported.

Hurricane Iris: Hurricane Iris of 2001 was the most destructive hurricane in Belize since Hurricane Hattie in 1961.  Iris was the second-strongest storm of the 2001 Atlantic hurricane season, behind Hurricane Michelle.  It was the ninth named storm, fifth hurricane, and third major hurricane of the year, forming from a tropical wave on October 4 just southeast of Barbados.  It moved westward through the Caribbean, intensifying into a tropical storm on October 5 south of Puerto Rico and into a hurricane the following day.  While passing south of the Dominican Republic, Iris dropped heavy rainfall that caused landslides, killing eight people.  Later, the hurricane passed south of Jamaica, where it destroyed two houses.  On reaching the western Caribbean Sea, Iris rapidly intensified into a Category 4 on the Saffir–Simpson scale.  A small hurricane with an eye of only 7 mi (11 km) in diameter, Iris reached peak winds of 145 mph (230 km/h) before making landfall in southern Belize near Monkey River Town on October 9.  The hurricane quickly dissipated over Central America, although its remnants contributed to the formation of Tropical Storm Manuel in the eastern Pacific Ocean.

Tropical Storm Beryl (2012): Tropical Storm Beryl was the strongest off-season Atlantic tropical cyclone on record to make landfall in the United States.  The second tropical cyclone of the 2012 Atlantic hurricane season, Beryl developed on May 26 from a low-pressure system offshore North Carolina.  Initially subtropical, the storm slowly acquired tropical characteristics as it tracked across warmer sea surface temperatures and within an environment of decreasing vertical wind shear.  Late on May 27, Beryl transitioned into a tropical cyclone less than 120 mi from North Florida.  Early the following day, the storm moved ashore near Jacksonville Beach, Florida, with peak winds of 65 mph (100 km/h).  It quickly weakened to a tropical depression, dropping heavy rainfall while moving slowly across the southeastern United States.  A cold front turned Beryl to the northeast, and the storm became extratropical on May 30.

Tropical cyclone rainfall forecasting: Tropical cyclone rainfall forecasting involves using scientific models and other tools to predict the precipitation expected in tropical cyclones such as hurricanes and typhoons.  Knowledge of tropical cyclone rainfall climatology is helpful in the determination of a tropical cyclone rainfall forecast.  More rainfall falls in advance of the center of the cyclone than in its wake.  The heaviest rainfall falls within its central dense overcast and eyewall.  Slow moving tropical cyclones, like Hurricane Danny and Hurricane Wilma, can lead to the highest rainfall amounts due to prolonged heavy rains over a specific location.  However, vertical wind shear leads to decreased rainfall amounts, as rainfall is favored downshear and slightly left of the center and the upshear side is left devoid of rainfall.  The presence of hills or mountains near the coast, as is the case across much of Mexico, Haiti, the Dominican Republic, much of Central America, Madagascar, Réunion, China, and Japan act to magnify amounts on their windward side due to forced ascent causing heavy rainfall in the mountains.  A strong system moving through the mid latitudes, such as a cold front, can lead to high amounts from tropical systems, occurring well in advance of its center.  Movement of a tropical cyclone over cool water will also limit its rainfall potential.  A combination of factors can lead to exceptionally high rainfall amounts, as was seen during Hurricane Mitch in Central America.

Hurricane Klaus: Hurricane Klaus was a minimal Atlantic hurricane that dropped heavy rainfall across the Lesser Antilles in October 1990.  The eleventh tropical cyclone and sixth hurricane of the 1990 Atlantic hurricane season, Klaus developed from a tropical wave on October 3 a short distance east of Dominica.  It drifted northwestward, and quickly intensified to attain hurricane status on October 5.  Though its closest approach to the Lesser Antilles was within 12 miles (19 km), the strongest winds remained to its northeast due to strong wind shear, which caused Klaus to steadily weaken.  After deteriorating into a tropical depression, Klaus briefly restrengthened over the Bahamas before dissipating on October 9 under the influence of developing tropical storm, Marco.

Hurricane Olga: Hurricane Olga was a late season Category 1 North Atlantic hurricane that formed during the 2001 Atlantic hurricane season.  The fifteenth named storm, ninth and final hurricane of the 2001 season, Olga formed as a subtropical cyclone on November 24.  After acquiring tropical characteristics later that day, Olga meandered westward, and eventually reached hurricane status on November 26.  Olga’s winds peaked at 90 mph (150 km/h) before the storm turned southwestward and weakening back into a tropical storm.  On November 30 it deteriorated further to a tropical depression, although it re-intensified two days later to tropical storm intensity.  Olga then dissipated as a tropical cyclone on December 4 east of the Bahamas.  Its damaging effects were limited to ships at sea.  The cyclone's remnants produced heavy rainfall across the Bahamas and Florida.  It was a relatively rare storm to exist in December, which is outside of the normal Atlantic hurricane season.

Tropical Storm Ana (2015): Tropical Storm Ana was the earliest recorded tropical cyclone to make landfall in the United States in any given year.  A relatively rare pre-season system, Ana was the first tropical storm of the 2015 Atlantic hurricane season.  It developed as a subtropical cyclone from a non-tropical low north of the Bahamas, and intensified to attain peak winds of 60 mph before transitioning into a fully tropical cyclone early on May 9.  Sustained in part by the warm waters of the Gulf Stream, Ana made landfall along the northeast coast of South Carolina early the next morning, becoming the earliest U.S. landfalling system on record.  Overall, damage from the storm was minor.  Heavy rainfall and gusty winds affected parts of the Carolinas, and some vulnerable beaches endured coastal flooding and several feet of erosion.  Gusty winds damaged trees and powerlines, causing sporadic power outages, and a weak tornado was reported in association with Ana.  In North Carolina, two deaths—one direct and one indirect—were attributed to the storm.

October 2008 Central America floods: The October 2008 Central America floods were caused by a series of low-pressure areas including Tropical Depression Sixteen, a short-lived tropical cyclone in the 2008 Atlantic hurricane season that made landfall in Honduras.  Heavy rainfall began in early October 2008 while a tropical wave passed through the region.  On October 14, Tropical Depression Sixteen formed just off the northeast coast of Honduras, and at the same time a low pressure system was on the Pacific coast.  Both systems increased rainfall across the region, although the depression dropped heavy rainfall close to its center when it moved ashore on October 15.  Although Tropical Depression Sixteen quickly dissipated over land, its remnants persisted for several days.  Another low pressure area interacted with a cold front on October 21, adding to the rainfall in the region.

Hurricane Abby (1968): Hurricane Abby made landfall in Cuba, Florida, and North Carolina in June 1968.  The first tropical cyclone, first named storm, and first hurricane on the season, Abby developed over the northwestern Caribbean Sea on June 1, as a result of the interaction between a mid-tropospheric trough and a cold front.  Moving generally north-northeastward, the depression slowly strengthened while approaching the western tip of Cuba, becoming Tropical Storm Abby late on June 2.  Shortly thereafter, Abby made landfall in Pinar del Río Province.  The storm dropped heavy rainfall in western Cuba, with up to 12 in on Isla de la Juventud.  However, no flooding was reported.  After reaching the southeastern Gulf of Mexico on June 3, Abby strengthened further and became a Category 1 hurricane on the modern-day Saffir–Simpson hurricane wind scale.  However, early on June 4, Abby weakened to a tropical storm.  Around midday on June 4, the system made landfall near Punta Gorda, Florida as a strong tropical storm.

Tropical Storm Marco (1990): Tropical Storm Marco was the only tropical cyclone to make landfall on the United States during the 1990 Atlantic hurricane season.  The 13th named storm of the season, Marco formed from a cold-core low pressure area along the northern coast of Cuba on October 9, and tracked northwestward through the eastern Gulf of Mexico.  With most of its circulation over the western portion of Florida, Tropical Storm Marco produced 65 mph (100 km/h) winds over land.  However, it weakened to a tropical depression before moving ashore near Cedar Key.  The cyclone combined with a cold front and the remnants of Hurricane Klaus to produce heavy rainfall in Georgia and the Carolinas.  After interacting with the nearby Hurricane Lili, Marco continued northward until being absorbed by a cold front on October 13.

Supporting paragraphs: Tropical Storm Marco (1990) Hurricane Klaus
Answer: 1990