Tropical cyclone rainfall climatology
Encyclopedia
A tropical cyclone rainfall climatology is developed to determine rainfall characteristics of past tropical cyclones. A tropical cyclone rainfall climatology can be used to help forecast current or upcoming tropical cyclone impacts. The degree of a tropical cyclone rainfall impact depends upon speed of movement, storm size, and degree of vertical wind shear. One of the most significant threats from tropical cyclone
s is heavy rainfall. Large, slow moving, and non-sheared tropical cyclones produce the heaviest rains. The intensity of a tropical cyclone appears to have little bearing on its potential for rainfall over land, but satellite measurements over the last several years show that more intense tropical cyclones produce noticeably more rainfall over water. Flooding from tropical cyclones remains a significant cause of fatalities, particularly in low-lying areas.
ing is common to tropical cyclones, there are factors which lead to excessive rainfall from tropical cyclones. Slow motion, as was seen during Hurricane Danny (1997)
and Hurricane Wilma
, can lead to high amounts of rainfall. The presence of mountains/hills near the coast, like across much of Mexico
, Haiti
, the Dominican Republic
, Central America
, Madagascar
, Réunion
, China
, and Japan
acts to magnify rainfall potential due to forced upslope flow into the mountains. Strong upper level forcing from a trough moving through the Westerlies and its associated cold front
, as was the case during Hurricane Floyd
, can lead to high amounts even from systems moving at an average forward motion. Larger tropical cyclones drop more rainfall as they precipitate upon one spot for a longer time frame than average or small tropical cyclones. A combination of two of these factors could be especially crippling, as was seen during Hurricane Mitch
in Central America
. During the 2005 season, flooding related to slow-moving Hurricane Stan
's broad circulation led to 1,662–2,000 deaths.
Isaac Cline
was the first to investigate rain
fall distribution around tropical cyclones in the early 1900s. He found that a larger proportion of rainfall falls in advance of the center (or eye) than after the center's passage, with the highest percentage falling in the right front quadrant. Father Viñes of Cuba
found that some tropical cyclones have their highest rainfall rates in the rear quadrant within a training (non-moving) inflow band. Normally, as a tropical cyclone intensifies, its heavier rainfall rates become more concentrated around its center. Rainfall is found to be heaviest in tropical cyclone's inner core, whether it be the eyewall or central dense overcast, within a degree latitude of the center, with lesser amounts farther away from the center. Most of the rainfall in tropical cyclones is concentrated within its radius of gale-force (34 knots/39 mph/63 km/h) winds. Rainfall is more common near the center of tropical cyclones overnight. Over land, outer bands are more active during the heating of the day, which can act to restrict inflow into the center of the cyclone. Recent studies have shown that half of the rainfall within a tropical cyclone is stratiform in nature. The chart to the right was developed by Riehl in 1954 using meteorological equations that assume a gale radius of about 140 miles (225.3 km), a fairly symmetric cyclone, and does not consider topographic effects or vertical wind shear. Local amounts can exceed this chart by a factor of two due to topography. Wind shear tends to lessen the amounts below what is shown on the table.
Larger tropical cyclones have larger rain shields, which can lead to higher rainfall amounts farther from the cyclone's center. This is generally due to the longer time frame rainfall falls at any one spot in a larger system, when compared to a smaller system. Some of the difference seen concerning rainfall between larger and small storms could be the increased sampling of rainfall within a larger tropical cyclone when compared to that of a compact cyclone; in other words, the difference could be the result of a statistical problem.
forces the rainfall pattern around a tropical cyclone to become highly asymmetric, with most of the precipitation falling to the left and downwind of the shear vector, or downshear left. In other words, southwesterly shear forces the bulk of the rainfall north-northeast of the center. If the wind shear is strong enough, the bulk of the rainfall will move away from the center leading to what is known as an exposed circulation center. When this occurs, the potential magnitude of rainfall with the tropical cyclone will be significantly reduced.
interacts with an upper-level trough
and the related surface front
, a distinct northern area of precipitation is seen along the front ahead of the axis of the upper level trough. This type of interaction can lead to the appearance of the heaviest rainfall falling along and to the left of the tropical cyclone track, with the precipitation streaking hundreds of miles or kilometers downwind from the tropical cyclone. The stronger the upper trough picking up the tropical cyclone, the more significant the left of track shift in the rainfall distribution tends to be.
in Central America
.
Globally, tropical cyclone rainfall is more common across the northern hemisphere than across the southern hemisphere. This is mainly due to the normal annual tropical cyclone distribution, as between half and two-thirds of all tropical cyclones form north of the equator. Rainfall is concentrated near the 15th parallel in both hemispheres, with a less steep dropoff seen with latitude across the northern hemisphere, due to the stronger warm water currents seen in that hemisphere which allow tropical cyclones to remain tropical in nature at higher latitudes than south of the equator. In the southern hemisphere, rainfall impacts will be most common between January and March, while north of the equator, tropical cyclone rainfall impacts are more common between June and November. Japan
receives over half of its rainfall from typhoons.
Between 1970-2004, inland flooding from tropical cyclones caused a majority of the fatalities in the United States
. This statistic changed in 2005, when Hurricane Katrina
's impact alone shifted the most deadly aspect of tropical cyclones back to storm surge
, which has historically been the most deadly aspect of strong tropical cyclones.
On average, five tropical cyclones of at least tropical depression strength lead to rainfall across the contiguous United States annually, contributing around a quarter of the annual rainfall to the southeast United States. While many of these storms form in the Atlantic Basin, some systems or their remnants move through Mexico from the Eastern Pacific Basin. The average storm total rainfall for a tropical cyclone impacting the lower 48 from the Atlantic Basin is about 16 inches (406 mm), with 70–75 percent of the storm total falling within a 24-hour period. The highest point total was seen during Amelia 1978
, when 48 inches (1,218 mm) fell upon central Texas
.
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
s is heavy rainfall. Large, slow moving, and non-sheared tropical cyclones produce the heaviest rains. The intensity of a tropical cyclone appears to have little bearing on its potential for rainfall over land, but satellite measurements over the last several years show that more intense tropical cyclones produce noticeably more rainfall over water. Flooding from tropical cyclones remains a significant cause of fatalities, particularly in low-lying areas.
Anticipating a flood event
While inland floodFlood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing is common to tropical cyclones, there are factors which lead to excessive rainfall from tropical cyclones. Slow motion, as was seen during Hurricane Danny (1997)
Hurricane Danny (1997)
Hurricane Danny was the only hurricane to make landfall in the United States during the 1997 Atlantic hurricane season, and the second hurricane and fourth tropical storm of the season...
and Hurricane Wilma
Hurricane Wilma
Hurricane Wilma was the most intense tropical cyclone ever recorded in the Atlantic basin. Wilma was the twenty-second storm , thirteenth hurricane, sixth major hurricane, and fourth Category 5 hurricane of the record-breaking 2005 season...
, can lead to high amounts of rainfall. The presence of mountains/hills near the coast, like across much of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, Haiti
Haiti
Haiti , officially the Republic of Haiti , is a Caribbean country. It occupies the western, smaller portion of the island of Hispaniola, in the Greater Antillean archipelago, which it shares with the Dominican Republic. Ayiti was the indigenous Taíno or Amerindian name for the island...
, the Dominican Republic
Dominican Republic
The Dominican Republic is a nation on the island of La Hispaniola, part of the Greater Antilles archipelago in the Caribbean region. The western third of the island is occupied by the nation of Haiti, making Hispaniola one of two Caribbean islands that are shared by two countries...
, Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
acts to magnify rainfall potential due to forced upslope flow into the mountains. Strong upper level forcing from a trough moving through the Westerlies and its associated cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
, as was the case during Hurricane Floyd
Hurricane Floyd
Hurricane Floyd was the sixth named storm, fourth hurricane, and third major hurricane in the 1999 Atlantic hurricane season. Floyd triggered the third largest evacuation in US history when 2.6 million coastal residents of five states were ordered from their homes as it approached...
, can lead to high amounts even from systems moving at an average forward motion. Larger tropical cyclones drop more rainfall as they precipitate upon one spot for a longer time frame than average or small tropical cyclones. A combination of two of these factors could be especially crippling, as was seen during Hurricane Mitch
Hurricane Mitch
Hurricane Mitch was the most powerful hurricane and the most destructive of the 1998 Atlantic hurricane season, with maximum sustained winds of 180 mph . The storm was the thirteenth tropical storm, ninth hurricane, and third major hurricane of the season. Along with Hurricane Georges, Mitch...
in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
. During the 2005 season, flooding related to slow-moving Hurricane Stan
Hurricane Stan
Hurricane Stan was the eighteenth named tropical storm and eleventh hurricane of the 2005 Atlantic hurricane season. It was also the sixth of seven tropical cyclones to make landfall in Mexico. Stan was a relatively weak storm that only briefly reached hurricane status...
's broad circulation led to 1,662–2,000 deaths.
General distribution within a tropical cyclone
| Rainfall Rate per day within radius of the center (Riehl) | |||
|---|---|---|---|
| Radius (mi) | Radius (km) | Amount (in) | Amount (mm) |
| 35 | 56 | 33.98 | 863 |
| 70 | 112 | 13.27 | 337 |
| 140 | 224 | 4.25 | 108 |
| 280 | 448 | 1.18 | 30 |
Isaac Cline
Isaac Cline
Isaac Monroe Cline was the chief meteorologist at the Galveston, Texas office of the US Weather Bureau from 1889 to 1901. In that role, he became an integral figure in the devastating Galveston Hurricane of 1900....
was the first to investigate rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
fall distribution around tropical cyclones in the early 1900s. He found that a larger proportion of rainfall falls in advance of the center (or eye) than after the center's passage, with the highest percentage falling in the right front quadrant. Father Viñes of Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
found that some tropical cyclones have their highest rainfall rates in the rear quadrant within a training (non-moving) inflow band. Normally, as a tropical cyclone intensifies, its heavier rainfall rates become more concentrated around its center. Rainfall is found to be heaviest in tropical cyclone's inner core, whether it be the eyewall or central dense overcast, within a degree latitude of the center, with lesser amounts farther away from the center. Most of the rainfall in tropical cyclones is concentrated within its radius of gale-force (34 knots/39 mph/63 km/h) winds. Rainfall is more common near the center of tropical cyclones overnight. Over land, outer bands are more active during the heating of the day, which can act to restrict inflow into the center of the cyclone. Recent studies have shown that half of the rainfall within a tropical cyclone is stratiform in nature. The chart to the right was developed by Riehl in 1954 using meteorological equations that assume a gale radius of about 140 miles (225.3 km), a fairly symmetric cyclone, and does not consider topographic effects or vertical wind shear. Local amounts can exceed this chart by a factor of two due to topography. Wind shear tends to lessen the amounts below what is shown on the table.
Relation to storm size
Slow/looping motion on rainfall magnitude
Storms which have moved slowly, or loop, over a succession of days lead to the highest rainfall amounts for several countries. Riehl calculated that 33.97 inches (863 mm) of rainfall per day can be expected within one-half degree, or 35 miles (56 km), of the center of a mature tropical cyclone. Many tropical cyclones progress at a forward motion of 10 knots, which would limit the duration of this excessive rainfall to around one-quarter of a day, which would yield about 8.50 inches (216 mm) of rainfall. This would be true over water, within 100 miles (160 km) of the coastline, and outside topographic features. As a cyclone moves farther inland and is cut off from its supply of warmth and moisture (the ocean), rainfall amounts from tropical cyclones and their remains decrease quickly.Vertical wind shear impact on rainfall shield
Vertical wind shearWind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
forces the rainfall pattern around a tropical cyclone to become highly asymmetric, with most of the precipitation falling to the left and downwind of the shear vector, or downshear left. In other words, southwesterly shear forces the bulk of the rainfall north-northeast of the center. If the wind shear is strong enough, the bulk of the rainfall will move away from the center leading to what is known as an exposed circulation center. When this occurs, the potential magnitude of rainfall with the tropical cyclone will be significantly reduced.
Effect of interaction with frontal boundaries/upper level troughs
As a tropical cycloneTropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
interacts with an upper-level trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
and the related surface front
Surface weather analysis
Surface weather analysis is a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations...
, a distinct northern area of precipitation is seen along the front ahead of the axis of the upper level trough. This type of interaction can lead to the appearance of the heaviest rainfall falling along and to the left of the tropical cyclone track, with the precipitation streaking hundreds of miles or kilometers downwind from the tropical cyclone. The stronger the upper trough picking up the tropical cyclone, the more significant the left of track shift in the rainfall distribution tends to be.
Mountains
Moist air forced up the slopes of coastal hills and mountain chains can lead to much heavier rainfall than in the coastal plain. This heavy rainfall can lead to landslides, which still cause significant loss of life such as seen during Hurricane MitchHurricane Mitch
Hurricane Mitch was the most powerful hurricane and the most destructive of the 1998 Atlantic hurricane season, with maximum sustained winds of 180 mph . The storm was the thirteenth tropical storm, ninth hurricane, and third major hurricane of the season. Along with Hurricane Georges, Mitch...
in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
.
Global distribution
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
receives over half of its rainfall from typhoons.
United States tropical cyclone rainfall statistics
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. This statistic changed in 2005, when Hurricane Katrina
Hurricane Katrina
Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...
's impact alone shifted the most deadly aspect of tropical cyclones back to storm surge
Storm surge
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
, which has historically been the most deadly aspect of strong tropical cyclones.
On average, five tropical cyclones of at least tropical depression strength lead to rainfall across the contiguous United States annually, contributing around a quarter of the annual rainfall to the southeast United States. While many of these storms form in the Atlantic Basin, some systems or their remnants move through Mexico from the Eastern Pacific Basin. The average storm total rainfall for a tropical cyclone impacting the lower 48 from the Atlantic Basin is about 16 inches (406 mm), with 70–75 percent of the storm total falling within a 24-hour period. The highest point total was seen during Amelia 1978
Tropical Storm Amelia (1978)
Tropical Storm Amelia was a weak, poorly-organized tropical storm that caused a severe flooding disaster in Texas during the 1978 Atlantic hurricane season. Amelia developed from a tropical wave on July 30 that entered an area of the Gulf of Mexico that was conductive for tropical cyclogenesis...
, when 48 inches (1,218 mm) fell upon central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
.
See also
- China tropical cyclone rainfall climatologyChina tropical cyclone rainfall climatologyChina is a mountainous country, which leads to rapid dissipation of cyclones that move inland as well as significant amounts of rain from those dissipating cyclones. Typhoon Nina caused the collapse of two huge reservoirs and ten smaller dams when 1062 mm/41.81 inches fell in Henan...
- Extratropical cycloneExtratropical cycloneExtratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
- List of wettest tropical cyclones by country
- Tropical cycloneTropical cycloneA tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
- Tropical cyclone rainfall forecastingTropical cyclone rainfall forecastingTropical 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...
- Tropical cyclogenesisTropical cyclogenesisTropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
- United States tropical cyclone rainfall climatologyUnited States tropical cyclone rainfall climatologyThe United States tropical cyclone rainfall climatology concerns the amount of precipitation, primarily in the form of rain, which occurs during tropical cyclones and their extratropical cyclone remnants across the United States...
Printed media
- Ivan Ray Tannehill. Hurricanes. Princeton University Press: Princeton, 1942.
- Herbert Riehl. Tropical Meteorology. McGraw-Hill Book Company, Inc.: New York, 1954.
- Terry Tucker. Beware the Hurricane! Hamilton Press: Bermuda, 1966.
Related external links
- Individual Tropical Cyclone Rainfall Pages for the United States and Mexico
- Individual Tropical Cyclone Rainfall Pages for Puerto Rico/U.S. Virgin Islands
- Maximum amounts in the lower 48 United States by state
- Typhoon Rainfall Statistics and Forecasting (China)
- Deadliest, Costliest, and Most Intense United States Tropical Cyclones From 1851 to 2004
- Are You Ready? Hurricanes
