Tropical Storm Ana (2009)
Encyclopedia
Tropical Storm Ana was the first named storm of the 2009 Atlantic hurricane season
and the first tropical cyclone
to impact the Caribbean islands
during 2009. Forming out of an area of low pressure
associated with a tropical wave
on August 11, Ana briefly attained tropical storm intensity on August 12 before weakening back to a depression. The following day, the system degenerated into a non-convective remnant low as it tracked westward. On August 14, the depression regenerated roughly 1,075 mi (1,735 km) east of the Leeward Islands
. Early on August 15, the storm re-attained tropical storm status, at which time it was named Ana. After reaching a peak intensity with winds of 40 mph (65 km/h) and a barometric pressure of 1003 mbar (hPa; 29.65 inHg), the storm began to weaken again due to increasing levels of wind shear
and the unusually fast movement of Ana. In post-storm analysis, it was discovered that Ana had degenerated into a tropical wave once more on August 16, before reaching any landmasses.
Numerous tropical storm watches
were issued for the Lesser Antilles
, Puerto Rico
, Dominican Republic
between August 15 and 17. Several islands took minor precautions for the storm, including St. Croix which evacuated 40 residents from flood-prone areas ahead of the storm. In the Dominican Republic, officials took preparations by setting up relief agencies and setting up shelters. Impact from Ana was minimal, mainly consisting of light to moderate rainfall. In Puerto Rico, up to 2.76 in (70.1 mm) of rain was reported, causing street flooding and forcing the evacuation of three schools.
(NHC) began monitoring a tropical wave
associated with a small area of convective activity
between the Cape Verde Islands and the western coast of Africa
. The system eventually spawned an area of low pressure
as it tracked towards the west. After slowly organising for a few days, the NHC reported early on August 11, that the system had developed into a tropical depression. The system at this time was located about 280 mi (455 km), west of the Cape Verde Islands. The depression developed deep convection around the center of circulation
and continued to track generally towards the west in response to a mid-level subtropical
ridge
to the north. The depression was expected to gradually intensify as it moved over marginally warm sea surface temperature
s and into an area of low wind shear
; however it was anticipated that dry air would hamper the depressions chances of intensifying further.
By August 12, the NHC reported that Tropical Depression Two was near tropical storm intensity after a burst of deep convection over the center. At this point, the system was not upgraded to a tropical storm; however, in a post-storm analysis, it was determined that the system had attained tropical storm-force winds, peaking at 40 mph (65 km/h) for 12 hours on August 12. Several hours later, the system became disorganized due to increased wind shear. By the afternoon of August 13, the system had weakened to a tropical depression and shortly thereafter, degenerated into a non-convective remnant low pressure area as it failed to maintain convection around the center for 24 hours. At this time, the NHC issued their final advisory on the system but noted that there was the possibility of regeneration.
On August 14, roughly 24 hours after degenerating into a remnant low, convection began to redevelop over the system. Later that day, a Hurricane Hunter reconnaissance plane deployed dropsonde
s into the system. They found that the system was regenerating and shortly after, the NHC began re-issuing advisories on the depression when it was located roughly 1,075 mi (1,735 km) east of the Leeward Islands
. The depression continued to track westward in response to an upper-level high over the north Atlantic. Early on August 15, the NHC upgraded the depression to a tropical storm, giving it the name Ana as deep convection developed around the center of circulation. Later that day, wind shear caused convection to become displaced from the circulation, exposing the center of Ana again.
By August 16, the forward motion of Ana began to increase, and the storm quickly entered a region of dry, stable air. By the afternoon, a Hurricane Hunter reconnaissance mission did not find any evidence of tropical storm-force winds, resulting in Ana being downgraded to a tropical depression. It was determined in post-storm analysis, that Ana had degenerated into a tropical wave shortly afterwards, and was no longer a tropical cyclone. Several hours later, the system redeveloped convection as it raced towards the west-northwest at 26 mph (42 km/h). Early on August 17, radar
imagery from Guadeloupe
and San Juan, Puerto Rico
depicted a system without a closed, low-level circulation. Despite this, the NHC continued operational advisories until confirmation could be made with visible satellite imagery. Later that day, a final reconnaissance plane flew into the storm and did not find a low-level circulation. Following this, the NHC stated that Ana had dissipated off the coast of Puerto Rico, despite having already degenerated into a tropical wave the previous day. The remnants of Ana were once more monitored for signs of regeneration but interaction with Hispanola and Cuba limited the system's chances.
was issued for much of the Leeward Islands
. Two days later, the watch was expanded to include Puerto Rico and areas in the eastern Dominican Republic
between Cabo Engaño
and Cabo Beata
. As Ana weakened and dissipated, the watches were discontinued.
In San Maarten, cruise agencies redirected ships to avoid the storm and secured vessels docked at port. Several ships were moved to Simpson Bay Lagoon where waves are generally small. In St. Kitts, officials evacuated 40 families in flood-prone areas to shelters ahead of the storm. On August 17, the National Weather Service
in San Juan, Puerto Rico
issued an Urban and Small Stream Flood Advisory for all of the eastern municipalities on the island. Flights in the area were delayed by several hours to avoid the depression. In the Dominican Republic, officials posted flood alerts for 12 provinces as the remnants of Ana were forecast to produce up to 6 in (152.4 mm) of rain in the country. General Luna Paulino of the civil army activated relief agencies ahead of the storm and notified residents of possible mandatory evacuations. Officials inspected the dams threatened by the storm to protect several towns and villages. Emergency officials stated that roughly 35,000 personnel were on standby in case of a disaster. Shelters were also prepped throughout the country; however, these were not opened and the residents who had voluntarily evacuated had returned home by the afternoon of August 17. In nearby Haiti, officials placed the country under yellow alert as the remnants of Ana could produce heavy rainfall over mountainous areas.
In St. Thomas
, sustained winds reached 28 mph (45 km/h) and gusts peaked at 40 mph (65 km/h). In Puerto Rico, rainfall was limited due to the storms' fast motion, triggering minor flooding but little damage. A maximum of 2.76 in (70.1 mm) of rain fell in Río Grande
. The rains caused the Río Fajardo
to rise, resulting in the issuance of an alert as officials warned it could overflow its banks. Several streets were temporarily shut down due to flooding, including one tunnel, and three schools had to be evacuated. Throughout the island, roughly 6,000 people were left without power as numerous branches were snapped off trees and knocked down power lines. There were also reports of waterspout
s and tornado
es associated with Ana in Puerto Rico. Winds on the island gusted up to 42 mph (67 km/h). The remnants of Ana produced widespread rainfall across Hispanola; however, there were no reports of damage from the system.
2009 Atlantic hurricane season
The 2009 Atlantic hurricane season was a below-average year, unlike the 2009 Pacific hurricane season, which was above average, both due to a moderate El Niño. During this year, nine tropical storms formed, the fewest since the 1997 season.An average season has ten tropical storms, six hurricanes...
and the first tropical cyclone
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...
to impact the Caribbean islands
Leeward Islands
The Leeward Islands are a group of islands in the West Indies. They are the northern islands of the Lesser Antilles chain. As a group they start east of Puerto Rico and reach southward to Dominica. They are situated where the northeastern Caribbean Sea meets the western Atlantic Ocean...
during 2009. Forming out of an area of low pressure
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
associated with a tropical wave
Tropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
on August 11, Ana briefly attained tropical storm intensity on August 12 before weakening back to a depression. The following day, the system degenerated into a non-convective remnant low as it tracked westward. On August 14, the depression regenerated roughly 1,075 mi (1,735 km) east of the Leeward Islands
Leeward Islands
The Leeward Islands are a group of islands in the West Indies. They are the northern islands of the Lesser Antilles chain. As a group they start east of Puerto Rico and reach southward to Dominica. They are situated where the northeastern Caribbean Sea meets the western Atlantic Ocean...
. Early on August 15, the storm re-attained tropical storm status, at which time it was named Ana. After reaching a peak intensity with winds of 40 mph (65 km/h) and a barometric pressure of 1003 mbar (hPa; 29.65 inHg), the storm began to weaken again due to increasing levels of wind shear
Wind 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...
and the unusually fast movement of Ana. In post-storm analysis, it was discovered that Ana had degenerated into a tropical wave once more on August 16, before reaching any landmasses.
Numerous tropical storm watches
Tropical cyclone warnings and watches
Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate...
were issued for the Lesser Antilles
Lesser Antilles
The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...
, Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
, 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...
between August 15 and 17. Several islands took minor precautions for the storm, including St. Croix which evacuated 40 residents from flood-prone areas ahead of the storm. In the Dominican Republic, officials took preparations by setting up relief agencies and setting up shelters. Impact from Ana was minimal, mainly consisting of light to moderate rainfall. In Puerto Rico, up to 2.76 in (70.1 mm) of rain was reported, causing street flooding and forcing the evacuation of three schools.
Meteorological history
On August 9, the National Hurricane CenterNational Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
(NHC) began monitoring a tropical wave
Tropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
associated with a small area of convective activity
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
between the Cape Verde Islands and the western coast of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. The system eventually spawned an area of low pressure
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
as it tracked towards the west. After slowly organising for a few days, the NHC reported early on August 11, that the system had developed into a tropical depression. The system at this time was located about 280 mi (455 km), west of the Cape Verde Islands. The depression developed deep convection around the center of circulation
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
and continued to track generally towards the west in response to a mid-level subtropical
Subtropical cyclone
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to the north. The depression was expected to gradually intensify as it moved over marginally warm sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s and into an area of low wind shear
Wind 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...
; however it was anticipated that dry air would hamper the depressions chances of intensifying further.
By August 12, the NHC reported that Tropical Depression Two was near tropical storm intensity after a burst of deep convection over the center. At this point, the system was not upgraded to a tropical storm; however, in a post-storm analysis, it was determined that the system had attained tropical storm-force winds, peaking at 40 mph (65 km/h) for 12 hours on August 12. Several hours later, the system became disorganized due to increased wind shear. By the afternoon of August 13, the system had weakened to a tropical depression and shortly thereafter, degenerated into a non-convective remnant low pressure area as it failed to maintain convection around the center for 24 hours. At this time, the NHC issued their final advisory on the system but noted that there was the possibility of regeneration.
On August 14, roughly 24 hours after degenerating into a remnant low, convection began to redevelop over the system. Later that day, a Hurricane Hunter reconnaissance plane deployed dropsonde
Dropsonde
A dropsonde is a weather reconnaissance device created by the National Center for Atmospheric Research , designed to be dropped from an aircraft at altitude to more accurately measure tropical storm conditions as the device falls to the surface...
s into the system. They found that the system was regenerating and shortly after, the NHC began re-issuing advisories on the depression when it was located roughly 1,075 mi (1,735 km) east of the Leeward Islands
Leeward Islands
The Leeward Islands are a group of islands in the West Indies. They are the northern islands of the Lesser Antilles chain. As a group they start east of Puerto Rico and reach southward to Dominica. They are situated where the northeastern Caribbean Sea meets the western Atlantic Ocean...
. The depression continued to track westward in response to an upper-level high over the north Atlantic. Early on August 15, the NHC upgraded the depression to a tropical storm, giving it the name Ana as deep convection developed around the center of circulation. Later that day, wind shear caused convection to become displaced from the circulation, exposing the center of Ana again.
By August 16, the forward motion of Ana began to increase, and the storm quickly entered a region of dry, stable air. By the afternoon, a Hurricane Hunter reconnaissance mission did not find any evidence of tropical storm-force winds, resulting in Ana being downgraded to a tropical depression. It was determined in post-storm analysis, that Ana had degenerated into a tropical wave shortly afterwards, and was no longer a tropical cyclone. Several hours later, the system redeveloped convection as it raced towards the west-northwest at 26 mph (42 km/h). Early on August 17, radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
imagery from Guadeloupe
Guadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
and San Juan, Puerto Rico
San Juan, Puerto Rico
San Juan , officially Municipio de la Ciudad Capital San Juan Bautista , is the capital and most populous municipality in Puerto Rico, an unincorporated territory of the United States. As of the 2010 census, it had a population of 395,326 making it the 46th-largest city under the jurisdiction of...
depicted a system without a closed, low-level circulation. Despite this, the NHC continued operational advisories until confirmation could be made with visible satellite imagery. Later that day, a final reconnaissance plane flew into the storm and did not find a low-level circulation. Following this, the NHC stated that Ana had dissipated off the coast of Puerto Rico, despite having already degenerated into a tropical wave the previous day. The remnants of Ana were once more monitored for signs of regeneration but interaction with Hispanola and Cuba limited the system's chances.
Preparations and impact
On August 15, a tropical storm watchTropical cyclone warnings and watches
Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate...
was issued for much of the Leeward Islands
Leeward Islands
The Leeward Islands are a group of islands in the West Indies. They are the northern islands of the Lesser Antilles chain. As a group they start east of Puerto Rico and reach southward to Dominica. They are situated where the northeastern Caribbean Sea meets the western Atlantic Ocean...
. Two days later, the watch was expanded to include Puerto Rico and areas in the eastern 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...
between Cabo Engaño
Cabo Engaño
Cabo Engaño is the easternmost point of the island of Hispaniola, on the territory of the Dominican Republic. Punta Cana International Airport, the nation's busiest, lies slightly south of the cape....
and Cabo Beata
Cabo Beata
Cabo Beata is the southernmost point of the island of Hispaniola, in the Pedernales Province of the Dominican Republic. The small island of Isla Beata stands about 4 mi southwest of the cape....
. As Ana weakened and dissipated, the watches were discontinued.
In San Maarten, cruise agencies redirected ships to avoid the storm and secured vessels docked at port. Several ships were moved to Simpson Bay Lagoon where waves are generally small. In St. Kitts, officials evacuated 40 families in flood-prone areas to shelters ahead of the storm. On August 17, the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
in San Juan, Puerto Rico
San Juan, Puerto Rico
San Juan , officially Municipio de la Ciudad Capital San Juan Bautista , is the capital and most populous municipality in Puerto Rico, an unincorporated territory of the United States. As of the 2010 census, it had a population of 395,326 making it the 46th-largest city under the jurisdiction of...
issued an Urban and Small Stream Flood Advisory for all of the eastern municipalities on the island. Flights in the area were delayed by several hours to avoid the depression. In the Dominican Republic, officials posted flood alerts for 12 provinces as the remnants of Ana were forecast to produce up to 6 in (152.4 mm) of rain in the country. General Luna Paulino of the civil army activated relief agencies ahead of the storm and notified residents of possible mandatory evacuations. Officials inspected the dams threatened by the storm to protect several towns and villages. Emergency officials stated that roughly 35,000 personnel were on standby in case of a disaster. Shelters were also prepped throughout the country; however, these were not opened and the residents who had voluntarily evacuated had returned home by the afternoon of August 17. In nearby Haiti, officials placed the country under yellow alert as the remnants of Ana could produce heavy rainfall over mountainous areas.
In St. Thomas
Saint Thomas, U.S. Virgin Islands
Saint Thomas is an island in the Caribbean Sea and with the islands of Saint John, Saint Croix, and Water Island a county and constituent district of the United States Virgin Islands , an unincorporated territory of the United States. Located on the island is the territorial capital and port of...
, sustained winds reached 28 mph (45 km/h) and gusts peaked at 40 mph (65 km/h). In Puerto Rico, rainfall was limited due to the storms' fast motion, triggering minor flooding but little damage. A maximum of 2.76 in (70.1 mm) of rain fell in Río Grande
Río Grande, Puerto Rico
Río Grande is a municipality of Puerto Rico located in the Northern Coastal Valley, North of Las Piedras, Naguabo and Ceiba; east of Loíza and Canóvanas and west of Luquillo. Río Grande is spread over eight wards and Río Grande Pueblo...
. The rains caused the Río Fajardo
Río Fajardo
-See also:*List of rivers of Puerto Rico-References:*USGS Hydrologic Unit Map – Caribbean Region *...
to rise, resulting in the issuance of an alert as officials warned it could overflow its banks. Several streets were temporarily shut down due to flooding, including one tunnel, and three schools had to be evacuated. Throughout the island, roughly 6,000 people were left without power as numerous branches were snapped off trees and knocked down power lines. There were also reports of waterspout
Waterspout
A waterspout is an intense columnar vortex that occurs over a body of water and is connected to a cumuliform cloud. In the common form, it is a non-supercell tornado over water. While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur...
s and tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es associated with Ana in Puerto Rico. Winds on the island gusted up to 42 mph (67 km/h). The remnants of Ana produced widespread rainfall across Hispanola; however, there were no reports of damage from the system.
See also
- Other storms of the same name
- Timeline of the 2009 Atlantic hurricane seasonTimeline of the 2009 Atlantic hurricane seasonThe 2009 Atlantic hurricane season was a below-average year in which nine tropical storms formed, the fewest since 1997.An average season has eleven tropical storms, six hurricanes and two major hurricanes. Although Tropical Depression One formed on May 28, 2009, the season officially began on...