Tropical Storm Grace (2009)
Encyclopedia
Tropical Storm Grace holds the record for being the farthest northeast forming tropical cyclone
in the Atlantic basin
. The seventh named storm of the slightly below average 2009 Atlantic hurricane season
, Grace formed from an extratropical cyclone
over the Azores
on October 4. It strengthened to attain peak sustained wind
s of 65 mph (100 km/h) and developed an eye-like feature
, although cold sea surface temperatures
inhibited the development of thunderstorm activity
near the center. The storm lost its tropical characteristics on October 6, though the remnants merged with a separate system near the British Isles.
Grace had only minor effects on land while it was passing through the Azores, where islands close to the storm's center recorded winds of up to 44 mph (71 km/h) and moderate rainfall. In Portugal, heavy rainfall led to some street flooding. although it was not solely related to the cyclone. In addition, its remnants produced nearly 2 inches (51 mm) of rain and tropical-storm-force winds in parts of Ireland and the United Kingdom.
that formed along a cold front on September 27, roughly 470 mi
(755 km
) east of Cape Race, Newfoundland. Initially attached to an occluded front
, the low detached from the system and gradually acquired tropical characteristics. By October 1, shower and thunderstorm activity began to develop near the center of the system as it tracked through the central Azores. However, the following day, convection began to decrease with Grace, and the National Hurricane Center
(NHC) ceased monitoring it. Over the following two days, the system executed a counter-clockwise loop near the Azores. During the afternoon of October 4, convection redeveloped around the center of the low and was classified as a tropical storm near São Miguel Island
. Although the storm was tropical at this time, the NHC did not issue advisories for several hours.
The first advisory from the NHC was issued at 11:00 AST
on October 4; at this time, the system was officially named Grace, the seventh named storm of the 2009 Atlantic hurricane season. The storm featured relatively deep convection around an eye-like feature
. Although Grace was over waters normally not warm enough for tropical cyclone development, low wind shear
allowed the convection to persist. A steady northeastward track was taken by the storm in response to a southerly flow over the northwestern Atlantic. The storm intensified slightly as it moved over decreasing sea surface temperatures, with winds estimated at 70 mph (110 km/h) early on October 5. However, in a post-storm analysis from the NHC, it was found that Grace attained peak winds of 65 mph (100 km/h), slightly lower than operationally stated.
A large extratropical cyclone near Grace caused the storm to deteriorate in organization, with convection weakening and becoming asymmetric. By this time, the storm was over 18 °C (64.4 °F) waters, likely inhibiting convective development. Shower and thunderstorm activity continued to diminish throughout the day on October 5; however, Grace maintained tropical characteristics, namely a deep, warm core. Early on October 6, the NHC issued their final advisory on Grace as it merged with a frontal system
over the northeastern Atlantic. Just prior to merging, the lowest pressure in relation to the storm was recorded at 986 mbar (hPa; 29.12 inHg). The extratropical remnants of Grace persisted for roughly 18 hours before dissipating over the Celtic Sea
early on October 7. However, the United States Naval Research Laboratory
continued to monitor the system for several more hours until it moved over the North Sea
.
Although officially designated a tropical cyclone by the NHC, Météo-France
, the French
meteorological service, stated in their annual report to the World Meteorological Organization
that Grace should not have been classified a tropical system. In their report, they argued that although the storm presented deep convection, an eye-like feature, and winds above 60 mph (95 km/h), the overall development of Grace was more similar to that of a mid-latitude non-tropical cyclone. However, operationally, Météo-France considered Grace to be a subtropical cyclone
. They also criticized the NHC of warning upon this system based on recent trends of the link between global warming
and increased hurricane activity.
. While merging with the frontal system on October 6, the storm's outer bands produced heavy rains and strong winds over parts of Portugal
, resulting in some street flooding. In higher elevations, wind gusts were estimated to have exceeded 80 km/h (49.7 mph).
Due to the storm's relatively rapid forward movement by the time it reached the United Kingdom, rainfall was limited. In Ireland, 1.18 in (30 mm) of precipitation fell in the city of Cork
. Sustained winds in the city were recorded up to 23 mph (37 km/h). Rainfall in the country peaked at 48 mm (1.9 in) in Wexford
. Near the coastline of Wales
, a buoy recorded sustained winds up to 41 mph (66 km/h), equivalent to a minimal tropical storm. Late on October 6, the remnants of Grace moved inland over Wales, bringing heavy rains and high winds to the region. Maximum rainfall in the United Kingdom reached 1.92 in (48.8 mm) in Capel Curig
. One ship, the Cap Castillo (call sign A8PI5), recorded sustained winds of 45 mph (72.4 km/h) on October 5, while located about 110 mi (177 km) south of the storm's center. Moisture from the storm's remnants fueled another, more powerful cyclone that caused flooding in parts of Belgium after producing upwards of 2.4 in (61 mm) of rain.
Operationally, Grace was not classified a tropical storm until it reached latitude 41.2°N. This marked the second northernmost formation of a tropical storm in the Atlantic on record; only Tropical Storm Alberto
of 1988 had formed farther north. However, a post-storm analysis concluded that Grace had actually become a tropical storm 12 hours earlier than initially estimated, placing its location of development further south, at 38.5°N. The storm still marked the farthest northeast a tropical cyclone formed in the Atlantic basin, breaking the record set by Hurricane Vince
in 2005.
In its Tropical Cyclone Report on Grace, the National Hurricane Center reported that the formation of Grace was poorly forecast. The first mention of the precursor low on October 1 predicted that it would not develop into a tropical or subtropical cyclone. Over the following three days, the system was not mentioned in the NHC's tropical weather outlooks until just prior to Grace's classification. The lack of preceding outlooks was attributed to the storm's unusual location and the sparsity of data for storms in the region.
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...
in the Atlantic basin
Atlantic Basin
The Atlantic Basin is the Atlantic Ocean.Atlantic Basin may also refer to:* Atlantic Basin Iron Works, an ironworks that operated in Brooklyn, New York, in the early to mid-20th century...
. The seventh named storm of the slightly below average 2009 Atlantic hurricane season
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...
, Grace formed from an extratropical cyclone
Extratropical cyclone
Extratropical 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...
over the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
on October 4. It strengthened to attain peak sustained wind
Maximum sustained wind
The maximum sustained winds associated with a tropical cyclone are a common indicator of the intensity of the storm. Within a mature tropical cyclone, they are found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unlike gusts, the value of these winds are...
s of 65 mph (100 km/h) and developed an eye-like feature
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...
, although cold sea surface temperatures
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...
inhibited the development of thunderstorm 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...
near the center. The storm lost its tropical characteristics on October 6, though the remnants merged with a separate system near the British Isles.
Grace had only minor effects on land while it was passing through the Azores, where islands close to the storm's center recorded winds of up to 44 mph (71 km/h) and moderate rainfall. In Portugal, heavy rainfall led to some street flooding. although it was not solely related to the cyclone. In addition, its remnants produced nearly 2 inches (51 mm) of rain and tropical-storm-force winds in parts of Ireland and the United Kingdom.
Meteorological history
Tropical Storm Grace originated from a large extratropical cycloneExtratropical cyclone
Extratropical 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...
that formed along a cold front on September 27, roughly 470 mi
Mile
A mile is a unit of length, most commonly 5,280 feet . The mile of 5,280 feet is sometimes called the statute mile or land mile to distinguish it from the nautical mile...
(755 km
Kilometre
The kilometre is a unit of length in the metric system, equal to one thousand metres and is therefore exactly equal to the distance travelled by light in free space in of a second...
) east of Cape Race, Newfoundland. Initially attached to an occluded front
Occluded front
An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front. When this occurs, the warm air is separated from the cyclone center at the Earth's surface...
, the low detached from the system and gradually acquired tropical characteristics. By October 1, shower and thunderstorm activity began to develop near the center of the system as it tracked through the central Azores. However, the following day, convection began to decrease with Grace, and the National Hurricane Center
National 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) ceased monitoring it. Over the following two days, the system executed a counter-clockwise loop near the Azores. During the afternoon of October 4, convection redeveloped around the center of the low and was classified as a tropical storm near São Miguel Island
São Miguel Island
São Miguel Island , nicknamed "The Green Island", is the largest and most populous island in the Portuguese Azores archipelago. The island covers and has around 140,000 inhabitants, 45,000 of these people located in the largest city in the archipelago: Ponta Delgada.-History:In 1427, São Miguel...
. Although the storm was tropical at this time, the NHC did not issue advisories for several hours.
The first advisory from the NHC was issued at 11:00 AST
UTC-4
UTC−04-00 is an identifier for a time offset from UTC of −04.This offset is used in the Atlantic Standard Time Zone in Canada and the North American Eastern Time Zone during daylight saving time , in the Caribbean region this is considered as the Eastern Caribbean timezone...
on October 4; at this time, the system was officially named Grace, the seventh named storm of the 2009 Atlantic hurricane season. The storm featured relatively deep convection around an eye-like feature
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...
. Although Grace was over waters normally not warm enough for tropical cyclone development, 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...
allowed the convection to persist. A steady northeastward track was taken by the storm in response to a southerly flow over the northwestern Atlantic. The storm intensified slightly as it moved over decreasing sea surface temperatures, with winds estimated at 70 mph (110 km/h) early on October 5. However, in a post-storm analysis from the NHC, it was found that Grace attained peak winds of 65 mph (100 km/h), slightly lower than operationally stated.
A large extratropical cyclone near Grace caused the storm to deteriorate in organization, with convection weakening and becoming asymmetric. By this time, the storm was over 18 °C (64.4 °F) waters, likely inhibiting convective development. Shower and thunderstorm activity continued to diminish throughout the day on October 5; however, Grace maintained tropical characteristics, namely a deep, warm core. Early on October 6, the NHC issued their final advisory on Grace as it merged with a frontal system
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
over the northeastern Atlantic. Just prior to merging, the lowest pressure in relation to the storm was recorded at 986 mbar (hPa; 29.12 inHg). The extratropical remnants of Grace persisted for roughly 18 hours before dissipating over the Celtic Sea
Celtic Sea
The Celtic Sea is the area of the Atlantic Ocean off the south coast of Ireland bounded to the east by Saint George's Channel; other limits include the Bristol Channel, the English Channel, and the Bay of Biscay, as well as adjacent portions of Wales, Cornwall, Devon, and Brittany...
early on October 7. However, the United States Naval Research Laboratory
United States Naval Research Laboratory
The United States Naval Research Laboratory is the corporate research laboratory for the United States Navy and the United States Marine Corps and conducts a program of scientific research and development. NRL opened in 1923 at the instigation of Thomas Edison...
continued to monitor the system for several more hours until it moved over the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
.
Although officially designated a tropical cyclone by the NHC, Météo-France
Météo-France
Météo-France is the French national meteorological service.The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operations have been decentralised to Toulouse...
, the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
meteorological service, stated in their annual report to the World Meteorological Organization
World Meteorological Organization
The World Meteorological Organization is an intergovernmental organization with a membership of 189 Member States and Territories. It originated from the International Meteorological Organization , which was founded in 1873...
that Grace should not have been classified a tropical system. In their report, they argued that although the storm presented deep convection, an eye-like feature, and winds above 60 mph (95 km/h), the overall development of Grace was more similar to that of a mid-latitude non-tropical cyclone. However, operationally, Météo-France considered Grace to be a subtropical cyclone
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...
. They also criticized the NHC of warning upon this system based on recent trends of the link between global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
and increased hurricane activity.
Impact and records
Upon being classified a tropical cyclone within the Azores, a few islands received minor rainfall and high winds. Gusts up to 44 mph (70.8 km/h) were recorded on Ponta DelgadaPonta Delgada
Ponta Delgada is a city and municipality on the island of São Miguel in the archipelago of the Azores, an autonomous region of Portugal. It includes 44,403 residents in the urban area, and approximately 20,113 inhabitants in the three central parishes that comprise the historical city: São Pedro,...
. While merging with the frontal system on October 6, the storm's outer bands produced heavy rains and strong winds over parts of Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, resulting in some street flooding. In higher elevations, wind gusts were estimated to have exceeded 80 km/h (49.7 mph).
Due to the storm's relatively rapid forward movement by the time it reached the United Kingdom, rainfall was limited. In Ireland, 1.18 in (30 mm) of precipitation fell in the city of Cork
Cork (city)
Cork is the second largest city in the Republic of Ireland and the island of Ireland's third most populous city. It is the principal city and administrative centre of County Cork and the largest city in the province of Munster. Cork has a population of 119,418, while the addition of the suburban...
. Sustained winds in the city were recorded up to 23 mph (37 km/h). Rainfall in the country peaked at 48 mm (1.9 in) in Wexford
Wexford
Wexford is the county town of County Wexford, Ireland. It is situated near the southeastern corner of Ireland, close to Rosslare Europort. The town is connected to Dublin via the M11/N11 National Primary Route, and the national rail network...
. Near the coastline of Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, a buoy recorded sustained winds up to 41 mph (66 km/h), equivalent to a minimal tropical storm. Late on October 6, the remnants of Grace moved inland over Wales, bringing heavy rains and high winds to the region. Maximum rainfall in the United Kingdom reached 1.92 in (48.8 mm) in Capel Curig
Capel Curig
Capel Curig is a village and community in Conwy County Borough, in Wales. It lies in the heart of Snowdonia, on the River Llugwy, and has a population of 226...
. One ship, the Cap Castillo (call sign A8PI5), recorded sustained winds of 45 mph (72.4 km/h) on October 5, while located about 110 mi (177 km) south of the storm's center. Moisture from the storm's remnants fueled another, more powerful cyclone that caused flooding in parts of Belgium after producing upwards of 2.4 in (61 mm) of rain.
Operationally, Grace was not classified a tropical storm until it reached latitude 41.2°N. This marked the second northernmost formation of a tropical storm in the Atlantic on record; only Tropical Storm Alberto
Tropical Storm Alberto (1988)
Tropical Storm Alberto was a tropical cyclone of the 1988 Atlantic hurricane season that became a tropical storm unusually far north. Alberto developed from a trough of low pressure off the coast of South Carolina on August 5...
of 1988 had formed farther north. However, a post-storm analysis concluded that Grace had actually become a tropical storm 12 hours earlier than initially estimated, placing its location of development further south, at 38.5°N. The storm still marked the farthest northeast a tropical cyclone formed in the Atlantic basin, breaking the record set by Hurricane Vince
Hurricane Vince (2005)
Hurricane Vince was an unusual hurricane that developed in the northeastern Atlantic basin. Forming in October during the 2005 Atlantic hurricane season, the waters over which it developed were considered too cold for tropical development...
in 2005.
In its Tropical Cyclone Report on Grace, the National Hurricane Center reported that the formation of Grace was poorly forecast. The first mention of the precursor low on October 1 predicted that it would not develop into a tropical or subtropical cyclone. Over the following three days, the system was not mentioned in the NHC's tropical weather outlooks until just prior to Grace's classification. The lack of preceding outlooks was attributed to the storm's unusual location and the sparsity of data for storms in the region.
See also
- Tropical cyclones named Grace
- 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...
- Hurricane Vince (2005)Hurricane Vince (2005)Hurricane Vince was an unusual hurricane that developed in the northeastern Atlantic basin. Forming in October during the 2005 Atlantic hurricane season, the waters over which it developed were considered too cold for tropical development...