Atlantic Hurricane Summary

2011
Atlantic Hurricane Summary
Hurricane Irene
Hurricane Katia
Hurricane Ophelia
Hurricane Rina
Weather Research Center
Houston, Texas
2011 Atlantic Tropical Storm/Hurricane Statistics and Summary
Name
Dates
Intensity
Cat
Arlene
Bret
Cindy
Don
Emily
Franklin
Gert
Harvey
Irene
Jose
Katia
Lee
Maria
Nate
Ophelia
Philippe
Rina
Sean
June 29 – July 1
July 17 – 22
July 20 – 23
July 27 – 30
August 1 – 7
August 12 – 14
August 14 – 16
August 19 – 22
August 20 – 29
August 28 – 29
August 29 – September 10
September 1 – 5
September 6 – 16
September 7 – 12
September 21 – October 3
September 24 – October 9
October 23 – 28
November 8 – 12
Tropical Storm
Tropical Storm
Tropical Storm
Tropical Storm
Tropical Storm
Tropical Storm
Tropical Storm
Tropical Storm
Hurricane
Tropical Storm
Hurricane
Tropical Storm
Hurricane
Hurricane
Hurricane
Hurricane
Hurricane
Tropical Storm
3
4
1
1
4
1
2
Lowest Pressure
MBS*
994
996
1000
998
1003
1004
1000
994
942
1007
946
986
979
994
940
976
966
983
*Lowest Pressure during the life of the storm.
**Highest maximum wind found during the life of the storm, taken from NHC advisories.
***To obtain wind speed in miles per hour (mph), multiply the wind in knots by 1.15.
Total Hurricanes
Total Major Hurricanes
Total Sub-Tropical Storms
Total Tropical Storms
Total US Landfalls
Total Named Tropical Cyclones
7
3
0
11
3
18
2011 Hurricane Season Timeline (Courtesy of Wikipedia)
Max Wind **
KTS***
55
55
50
45
45
40
50
50
105
40
115
50
70
60
120
80
95
55
Deaths
19
0
0
0
5
0
0
3
49
0
3
3
0
5
0
0
UNK
1
Season Highlights
The 2011 hurricane season began in earnest in late June at approximately the same time of the year as the
previous season. While the past two seasons were comparable in timing, there was more activity in the tropics
in the first half of the season. Although no hurricanes developed prior to mid-August, seven named storms had
reached tropical storm status by that time. Tropical Storm Arlene developed on June 28 over the Bay of
Campeche. Arlene intensified to a strong tropical storm before landfall along the coast of Mexico, where flash
flood conditions led to the 18 fatalities.
Three tropical storms formed in the month of July. Bret and Cindy both developed from the same frontal trough
moving off the east coast of the United States and eventually became enveloped in southwesterly flow aloft and
dissipated. Tropical Storm Don formed over the Yucatan Channel from a tropical wave and eventually made its
way into southern Texas, where it provided a small amount of relief from local drought. July ended without any
hurricanes, which last happened in the 2009 season.
Tropical Storm Emily started off the most active and intense month of the 2011 hurricane season on August 1.
Triggered by a tropical wave, this system affected portions of the Lesser Antilles, Hispaniola, Cuba, and the
Bahamas before eventually being pushed off to the northeast by upper level winds off the east coast of the
United States. Tropical Storm Franklin developed north of Bermuda on August 12 and dissipated soon
thereafter. Tropical Storm Gert formed south of Bermuda then tracked north near the island without inflicting
damage.
After Tropical Storm Harvey developed from a tropical wave off the coasts of Honduras and Nicaragua, it made
landfall over Belize, tracked across the Yucatan Peninsula then entered the Gulf of Mexico before making a
second landfall near Veracruz, Mexico. Not only did Harvey form in the most active month of the season, but it
also started the longest continual stretch of tropical activity in the Atlantic when it developed from a tropical
wave on August 19.
Hurricane Irene began its life as a named storm on August 21. Irene’s storm track would result in torrential rains
along a path through the Leeward Islands, Puerto Rico, just north of Hispaniola and into the Bahamas. At that
point, Irene reached its maximum strength and became the first major hurricane of the season before turning
northward toward the east coast of the United States. Hurricane Irene weakened before making landfall over
North Carolina, but the storm would still be able to bring torrential rain to the Atlantic coast and cause
widespread flooding across the mid-Atlantic and northeast.
Tropical Storm Jose exhibited a short lifespan starting initially southwest of Bermuda on August 28 before
dissipating mid-way between Halifax and Bermuda the next day.
The final storm initiated in August would not only become the second hurricane of 2011 in the Atlantic, but also
the second major hurricane of the season. Hurricane Katia originated south of Cape Verde from a tropical wave
and tracked west-northwest until nearing Bermuda. South of Bermuda, Katia became a Category 4 hurricane
and would subsequently round Bermuda on the west side of the island before weakening and dissipating as it
turned north and east along Nova Scotia and Newfoundland. In all, one tropical depression, five tropical storms
and two major hurricanes developed between August 1 and 31.
During Katia’s lifespan, Tropical Storm Lee developed from a tropical wave on September 2 and later become
the third and final named storm of the Atlantic hurricane season to make landfall on the U.S. coastline.
Hurricane Nate formed on September 7 along a stationary front oriented over the Gulf of Mexico and made
landfall north of Veracruz, Mexico on September 11. Hurricane Maria, which was generated by a tropical wave
one day prior to Nate, initially moved westward toward the Lesser Antilles before turning to the northwest over
the Leeward Islands. Maria’s storm track continued to curve to the north then northeast, causing the storm to
remain over water. As Hurricane Maria dissipated on the southeastern coast of Newfoundland on September
16, twenty-nine days of continuous tropical activity in the Atlantic came to an end. This was the third longest
such stretch since 2004.
A tropical wave initiated the strongest hurricane of the year on September 20, as Hurricane Ophelia began to
move toward the Leeward Islands. Ophelia stalled and weakened at the northern edge of the Lesser Antilles for
a period of time before restrengthening and tracking toward Bermuda. Hurricane Ophelia reached peak
intensity just east of Bermuda and rapidly dissipated afterwards as it approached Nova Scotia. Ophelia was the
last major hurricane of the season, bringing the total to three.
Hurricane Philippe developed on September 24 south of Cape Verde by a tropical wave and meandered across
the North Atlantic before strengthening in the vicinity of Bermuda and dissipated shortly thereafter. Ophelia
and Philippe brought September to a close and for the first time since 2009 and the second time since 2004,
September was outpaced by August in activity.
Hurricane Rina formed on October 23 and reached peak intensity off the coast of Honduras and weakened as it
tracked toward Isla Cozumel before making landfall as a tropical storm and subsequently dissipating on October
28. The final tropical storm of the season was Sean, which originated on November 8 as a subtropical storm
associated with a frontal trough off of the east coast before tracking north and east and eventually dissipating.
Following Sean, the Atlantic hurricane season quieted and came to an end.
National Summary
1. Tropical Storm ARLENE: June 28 - July 1, 2011 - Yucatan Peninsula; South of Tampico, Mexico
Arlene began from a tropical wave, which moved off of the coast of West Africa
on June 13. Thunderstorms associated with this wave had noticeably increased
by the June 25 and over the course of the following days, the storm was steered
toward the northwest by upper level winds over Central America. A definitive
circulation became evident after June 27, as the beginnings of Arlene crossed the
Yucatan Peninsula and into the warm ocean waters of the Bay of Campeche the
next day. Arlene was estimated to have reached tropical storm status on the
afternoon of June 28 and an initial advisory was issued that night, by which time
Arlene had been categorized as a tropical storm and the first named storm of the
year. Arlene reached peak intensity with maximum sustained winds of 55 knots just before landfall south of
Tampico, Mexico on the morning of June 30. Arlene quickly dissipated following landfall over Mexico on July 1.
According to the National Hurricane Center, reports indicated that 18 people died directly due to Arlene and one
indirectly with most of the deaths attributed to fresh water floods and mudslides.
2. Tropical Storm BRET: July 17 - 22, 2011
Following the passage of a low pressure system off of the east coast of the
United States in early July, the cold front associated with the low became
stationary. Following multiple days of the stationary front persisting off of the
eastern seaboard, development of a new pressure minimum began on July 16,
just east of Florida’s Atlantic coastline. With the combination of warm ocean
waters and decreasing upper level winds, the new low pressure system was
classified as the second tropical depression of the season in the early afternoon
on July 17. Later that night, the depression strengthened into Tropical Storm
Bret. Bret’s initial storm motion was briefly directed toward the southeast
before upper level winds began steering the storm toward the northeast. Tropical Storm Bret reached a
maximum intensity of 60 knots on July 18. Over the course of the next few days, Bret continued to weaken as its
movement toward the northeast brought the storm into increasingly poor environmental conditions. On the
morning of July 22, Bret was downgraded to a Tropical Depression and became post tropical later that day.
3. Tropical Storm CINDY: July 20 - 22, 2011
Cindy’s unexpected genesis resulted from the same stationary front responsible
for the development of Bret. An additional low pressure center began to develop
to the northeast of Bret in favorable environmental conditions. This system
moved to the northeast due to similar upper level steering that affected Bret. A
well-defined center was visible early on July 20 and later that day, the low
became Tropical Storm Cindy. Cindy reached a peak intensity of 60 knots at
1800 UTC on July 21. Cindy’s track quickly took the storm into cooler waters and
closer to strong upper level shear. As a result, winds associated with Tropical
Storm Cindy progressively weakened over the course of the day and Cindy became a post-tropical cyclone late
on July 22.
4. Tropical Storm DON: July 27 - 30, 2011 - South of Corpus Christi, Texas
A tropical wave originating off the west coast of Africa on July 16, with a history
of causing intermittent convection as it traversed the tropical Atlantic, became
more organized as it approached the Yucatan Channel and triggered the
development of a low pressure system early on July 27. The combination of
relatively weak upper level shear and considerably warm sea surface
temperatures allowed for continued development and increased thunderstorm
activity, despite of the presence dry air aloft. The low intensified into Tropical
Storm Don later that day. Upper level winds pushed Don along a westnorthwesterly track that would eventually lead it toward the southern Texas
coast. Tropical Storm Don reached maximum intensity of 45 knots late on July 28, while over the central Gulf of
Mexico. Don made landfall south of Corpus Christi, Texas as a weak tropical storm late on July 29, then quickly
weakened into a tropical depression. Tropical Storm Don proved to be only moderately beneficial in delivering
much needed moisture to drought stricken areas that it moved over. The highest measured rainfall total
associated with Don was 2.56 inches in Bay City Texas.
5. Tropical Storm EMILY: August 1 - 6, 2011 - Les Cayes, Haiti; Nassau, Bahamas
Emily developed from an area of unorganized thunderstorms triggered by a
tropical wave progressing westward off the African coast on July 25. This
disturbance began to exhibit some organization and rotation by the end of the
month. On the afternoon of August 1, just prior to impacting the Lesser Antilles,
Emily became the fifth named tropical storm of the season. Steering winds kept
Tropical Storm Emily on a track over much of the Caribbean, including the Lesser
Antilles, Puerto Rico, Hispaniola, and Cuba, bringing torrential rains. Emily’s
development would be hindered throughout its lifespan by unfavorable
environmental conditions. Emily reached peak intensity on August 2 with winds
of 55 knots that persisted for almost 48 hours. The system was downgraded to a tropical depression on the
afternoon of August 6 and dissipated twenty-four hours later.
6. Tropical Storm FRANKLIN: August 12 - 13, 2011
In early August, a stationary front located north of Bermuda led to the
development of the sixth named storm of the 2011 hurricane season. An area of
low pressure began initial formation along the front on August 12.
Thunderstorm activity began to increase and become organized and the new low
was categorized as a tropical depression later that day. Upper level steering
winds influenced an east/northeasterly track that would remain generally
unchanged throughout the lifecycle of the storm. Early on the morning of
August 13, Franklin was named as a tropical storm with sustained winds of 35
knots. However, the presence of strong upper level shear and increasingly cold surface temperatures hindered
significant intensification and Franklin only briefly attained peak winds of 40 knots. By August 14, Franklin
became a post-tropical cyclone before dissipating into a trough of low pressure about 500 nautical miles away
from the Azores.
7. Tropical Storm GERT: August 13 - 16, 2011
In the second week of August, a weak low pressure area associated with a frontal
trough and related occluded front provided enough instability for the triggering
of disorganized thunderstorms. The system became better organized and the
low subsequently became a tropical depression early in the afternoon on August
13. The initial storm track was to the north-northwest, but the depression
veered toward the east as it moved over a ridge of high pressure. About 24
hours later, Tropical Depression Eight had been upgraded to Tropical Storm Gert.
Gert reached peak intensity of 55 in the morning on August 15 before quickly
dissipating over relatively cool ocean waters.
8. Tropical Storm HARVEY: August 19 - 22, 2011 - South of Belize City, Belize; Veracruz, Mexico
A tropical wave exhibited repeated thunderstorm development over the tropical
Atlantic moved off the West African coast on August 10. Warm sea surface
temperatures and weak shear aloft allowed increased convective activity during
the third week of August and as the wave slowed its westward progression over
these favorable environmental conditions, a closed surface low developed. Late
on August 18, the eighth tropical depression of the season had formed. Twelve
hours later, the depression strengthened into Tropical Storm Harvey. A ridge of
high pressure over the Gulf of Mexico steered the storm on a west/northwest
track that brought Harvey’s first landfall south of Belize City, Belize early in the
afternoon on August 20. During landfall, Harvey reached a peak intensity of 55 knots. Harvey weakened to a
tropical depression on the morning of August 21 as it moved across the Yucatan Peninsula. The storm then
moved over the Bay of Campeche later that day and briefly regained tropical storm strength before it made its
second landfall near Veracruz, Mexico. Tropical Storm Harvey finally dissipated as it moved over mountainous
terrain in the interior of Mexico. According to the Associated Press, over three hundred homes were damaged
in Veracruz by flooding resulting from Tropical Storm Harvey and three people were killed by a Harvey induced
mudslide which occurred in Oaxaco.
9. Hurricane IRENE: August 21 - 28, 2011 - Guadalupe; Ponce, Puerto Rico; Governor’s Harbour, Bahamas;
Cape Lookout, North Carolina; Atlantic City, New Jersey
The ninth named storm of the 2011 hurricane season, Irene, initially developed
due to a tropical wave moving westward just off of the African coast on August
15. Organized thunderstorms were observed on August 17, and Irene was
categorized as a tropical storm as it approached landfall over the Lesser Antilles
late on August 20. Upper level winds initially steered Irene on a west-northwest
track, which led it over increasingly warmer ocean waters. Irene continued to intensify and reached hurricane
strength shortly after landfall on August 22, becoming the first Atlantic hurricane of 2011. As Irene moved over
the Caribbean during the next two days, upper level winds associated with a high became predominantly
southeasterly. The hurricane’s track followed suit as it continued to head through a favorable environment and
over warm ocean waters as it tracked toward the Bahamas. Irene was upgraded to a Category 2 on the morning
of August 24 and to a Category 3 hurricane just three hours later. At that time, the hurricane reached peak
intensity with sustained winds of 105 knots. On August 26, as Irene’s center of rotation began moving away from
the Bahamas and closer to the US, the hurricane drew closer to a stationary front located along the east coast.
This front would eventually push Irene onto a northerly track over progressively cooler waters that would
weaken Hurricane Irene from a Category 3 status to a Category 1 status prior to its eventual landfall over the
mid-Atlantic coastline. Irene made landfall on the North Carolina coast near Cape Lookout in the morning on
August 27 with an intensity of 75 knots. Later that day, Irene started to become incorporated into the cold front
still located over the east coast and continued to weaken in the absence of warm sea surface temperatures and
the addition of stronger upper level shear. Following a crossing of the North Carolina/southeastern Virginia
coast, the hurricane’s center of circulation passed over the mouth of the Chesapeake Bay and remained off the
coast until a final landfall over Atlantic City, New Jersey on August 28. Irene weakened to a tropical storm later
that day and became post-tropical that evening. Irene was not only the first hurricane of the season but also the
first major hurricane of the year in the Atlantic Ocean. Over 20 inches of rain was dropped by Irene in some
places in Puerto Rico and 49 deaths were attributed to Irene in the Dominican Republic, Haiti and the United
States. Although it did not make landfall over the United States prior to weakening to a Category 1 hurricane,
Irene caused widespread damage along the coast of the U.S. This was primarily due to flash-flooding in New
Jersey, Vermont and Massachusetts as Irene caused torrential rains over land that was already well saturated.
The case illustrates that the hazards of hurricanes reach far beyond the strong winds and resulting storm surge
associated with such storms.
10. Tropical Storm JOSE: August 28 - 29, 2011
During the fourth week of August, a tropical wave moving across the North
Atlantic after leaving the African coast on August 19 triggered an area of
thunderstorm activity southeast of Bermuda. By August 25, the thunderstorms
became more organized and began to exhibit circulation as they tracked
westward. As this storm drew closer to the U.S. coast, upper level winds diverted
by Irene began to steer the newly organized system northward toward Bermuda.
On the morning of August 28, Tropical Storm Jose was named with sustained
winds of 35 knots. Jose reached maximum intensity approximately 9 hours later
at 50 knots. As the storm moved northward, it encountered increasing amounts
of upper level shear on the southeast side of Irene and progressively cooler sea surface temperatures. Jose
dissipated on August 29, prior to making landfall over Bermuda.
11. Hurricane KATIA: August 29 - September 10, 2011
Late in the month of August, a tropical wave originating off of the West African
coast on August 27 passed through an area of relatively warm ocean waters and
weak upper lever shear. The combination rapidly initiated an area of convection.
Over the course of the next day, the system exhibited increasingly organized
circulation and on the morning of August 29, it was categorized as a tropical
depression. Over the next 24 hours, the depression strengthened into Tropical
Storm Katia. By September 1, Katia was upgraded to hurricane status. At this
approximate time, winds aloft began to slowly direct Katia on a more
northwestward course that would eventually track the hurricane north of the
Lesser Antilles. Katia would be downgraded to a tropical storm and subsequently upgraded to a hurricane twice
as it passed through areas of relatively strong upper-level shear before encountering favorable environmental
conditions and becoming a Category 2 hurricane on September 4. Hurricane Katia formed a well-developed eye
in the morning on September 5 and later that day became the second major hurricane of the 2011 season and
reaching Category 4 strength with winds of 115 knots. Shortly thereafter, Hurricane Katia began an eyewall
replacement cycle, weakening the storm to a Category 2 hurricane on September 6, and subsequently
weakening to a Category 1 hurricane approximately twenty-four hours later. As Hurricane Katia weakened, it
encountered a stationary front located over the east coast and began to move toward the north. Katia briefly
strengthened to a Category 2 again, but later on September 8, the storm tracked over relatively cool ocean
waters, keeping Katia a Category 1 hurricane for the rest of its lifecycle.
12. Tropical Storm LEE: September 2 - 5, 2011 - Intracoastal City, Louisiana
A tropical wave originating off the African coast on 18 August encountered
favorable sea surface temperatures over the Gulf of Mexico, resulting in
increased organization of already existing thunderstorm activity and the
development of Tropical Depression 13 on September 2. With very little upper
level steering present, TD 13 lingered over the Gulf of Mexico with a slight
movement northward of approximately 2 knots due to weak steering currents.
Later that day, the depression strengthened to Tropical Storm Lee. Lee slowly
moved northward and began to take on subtropical characteristics as the storm
merged with an upper-level low. Tropical Storm Lee reached peak intensity on
September 3 with winds of 50 knots before once again lingering off of the Louisiana coast as it weakened after
encountering a dry air layer. Early on September 4, Lee turned toward the east-northeast and moved inland
along the coast of southern Louisiana near Intracoastal City. Winds decreased after landfall and Lee eventually
became stationary and was downgraded to a tropical depression on September 5. Fifteen deaths were
attributed to Lee or its remnants, with most occurring when individuals attempted to navigate flooded
roadways.
13. Hurricane MARIA: September 6 - 16, 2011
Following increasing organization of thunderstorms off of West Africa
associated with a tropical wave exiting the coast on September 3, the
fourteenth tropical depression of the season formed on September 6. The
system moved on track toward the west throughout the day on September 7
and began to develop a circulation. The depression was upgraded to a tropical
storm the same day, making Maria the 13th named storm of the 2011 Atlantic
hurricane season. Tropical Storm Maria was located in an area with moderately
strong upper level shear, which inhibited further development for a few days.
Maria continued to move westward until mid-way through September 9, when
southeasterly upper level winds began to push it onto a northwestern track that resulted in heavy rains and
strong winds over the northern Lesser Antilles on September 10. By September 13, an area of high pressure
passed to the north of Tropical Storm Maria and southerly winds aloft associated with the high changed Maria’s
path to the north. This northward track steered Maria toward Bermuda and into a more favorable environment.
Maria began to strengthen as it passed Bermuda and on the afternoon of September 15, it was upgraded to a
hurricane. Hurricane Maria reached peak intensity maximum sustained winds of 70 knots with gusts of up to 85
knots late on September 15 and became extratropical the next day.
14. Hurricane NATE: September 7 - 11, 2011 - North of Veracruz, Mexico
On the afternoon of September 7, Tropical Storm Nate developed following the
organization of previously scattered thunderstorms along a stationary front over
the Gulf of Mexico. With little steering currents, Nate lingered in an area of low
to mid-level dry air and, otherwise, favorable environmental conditions over the
Gulf of Mexico. Subsequent data indicates that Nate reached peak intensity and
hurricane status around on September 8, before once again weakening to
tropical storm status early the next morning. In response to a building high
pressure system, Nate moved westward toward the coast of Mexico and made
landfall north of Veracruz, Mexico on September 11 with maximum sustained
winds of 50 knots with gusts of up to 60 knots. The storm was downgraded to a tropical depression later that
day. Five deaths are attributed to Nate.
15. Hurricane OPHELIA: September 20 - October 3, 2011
A tropical wave moved off of the west coast of Africa on September 16 and
became organized over the next few days, before developing into Tropical Storm
Ophelia on September 20 over the central Atlantic. Steering winds aloft favored a
track westward toward the Lesser Antilles, which Ophelia followed until slightly
curving to the west-northwest late on September 22. Shortly thereafter,
development began to stall as Tropical Storm Ophelia encountered areas of
strong upper level shear. Nonetheless, Ophelia continued toward the Leeward
Islands until September 25. At that time, weak upper level winds caused Ophelia
to stall just to the east of the Leeward Islands in poor environmental conditions and the system became
classified as an extratropical cyclone. It would not be until the morning of September 27 that Ophelia would
restrengthen to a tropical depression following weakening upper level shear. The onset of favorable
environmental conditions allowed Ophelia to strengthen, becoming a tropical storm on September 28, as it
moved to the northwest. The following day, Ophelia became the fifth hurricane of the season. Hurricane
Ophelia was then upgraded to a Category 2 then to a Category 3 in the next 12 hours. Ophelia, now the third
major Atlantic hurricane of 2011, continued northward toward Bermuda with a progressively more distinctive
eye resulting from favorable upper level shear and sufficiently warm sea surface temperatures. On October 2,
Ophelia reached peak intensity and became a Category 4 hurricane as it passed Bermuda, with maximum
sustained winds of 120 knots. However, Hurricane Ophelia began to rapidly dissipate as it moved into
increasingly poor environmental conditions and became extratropical on October 3.
16. Hurricane PHILIPPE: September 24 - October 9, 2011
Tropical Depression 17 was identified on September 24 after it had developed
organized thunderstorms as an easterly wave moved south of the Cape Verde
Islands. Later that day, the depression was upgraded to Tropical Storm Philippe.
Philippe’s west-northwest motion became predominantly directed toward the
northwest due to a strengthening high pressure system to the east. While this
storm track was located near only weak upper level shear, sea surface
temperatures around the area of Cape Verde were relatively cool and hindered
Philippe’s development into a hurricane. When tropical storm Philippe began to
move over warmer ocean waters by October 2, a developing high to the north of
Philippe forced it to move along a new track to the southwest. This lasted until October 5, when a strong trough
moving eastward redirected Philippe northward towards the warm waters of Bermuda. As the tropical storm
moved northward into light shear prior to encountering prevailing westerly winds, Philippe began to gradually
strengthen. Philippe became the sixth hurricane of the year by on October 6 and later that day reached peak
intensity with maximum sustained winds of 80 knots and gusts of up to 100 knots. Hurricane Philippe rapidly
encountered increasingly strong upper level shear associated with the strong frontal trough approaching the
hurricane from the west and was downgraded to a tropical storm by on October 7.
17. Hurricane RINA: October 23 - 28, 2011 - Playa del Carmen, Mexico
The eighteenth tropical depression of the season developed on October 23 as a
tropical wave emerging off the north coast of South America on October 20 was
observed passing aloft over a stationary front oriented from Cuba to Nicaragua,
resulting in an increasingly organized area of thunderstorms. Later that night,
the tropical depression was upgraded to Tropical Storm Rina. In lieu of strong
upper level winds, a strengthening area of high pressure to the east put Rina on
a storm track to the northwest at approximately 5 knots. With a combination of
warm sea surface temperatures and moderate shear, Rina became the seventh
hurricane of the year on October 24. Rapid development continued, as Rina was
upgraded to a Category 2 hurricane in the morning on October 25 and reached peak intensity later that night
with maximum sustained winds of 95 knots, gusting to 115 knots, very close to Category 3 status strength.
Shortly thereafter, Hurricane Rina began to weaken as it approached land. Rina made landfall near Playa del
Carmen, Mexico as a strong tropical storm on October 27. Tropical Storm Rina dissipated further as it
encountered very strong upper level shear while moving into the Yucatan Channel and became extratropical on
October 28. The most notable incident involving Hurricane Rina occurred when a Nicaraguan navy vessel and its
twenty-nine passengers went missing on October 23. The vessel’s four member crew and twenty-five evacuees
were found two days later.
18. Tropical Storm SEAN: November 8 – 12, 2011
The final named storm of the season came late in the year, as a developing low
associated with a frontal trough moving off of the east coast of the United
States in the first week of November became stationary over relatively warm
ocean waters northeast of the Bahamas. The low strengthened and was
classified as Subtropical Storm Sean on November 8. The upper level flow which
first allowed Sean to become stationary remained weak and the storm initially
lingered between the Bahamas and Bermuda. Later that day, Sean was acquired
tropical characteristics and was upgraded to a tropical storm. Tropical Storm
Sean reached peak intensity on November 9 with maximum sustained winds of
55 knots and gusts of up to 65 knots. On November 10, Sean began moving to the northeast ahead of a cold
front approaching the east coast of the United States. Strong upper level winds associated with the front drew
close to Sean causing it to weaken and become extratropical on November 12.
®
5104 Caroline
Weather Research Center
Houston, Texas 77004
Phone: 713-529-3076
Fax: 713-528-3538
E-mail: wrc@wxresearch.org
For Immediate Release
November 29, 2011
For information, call 713-529-3076
WRC’s 2011 Hurricane Outlook Verified When Tropical Storm Lee
Made Landfall in Louisiana
Houston, TX – According to WRC meteorologist, Jill F. Hasling, there was a 90 percent
chance of a tropical storm or hurricane making landfall along the Gulf Coast from
Louisiana to Key West, Florida during the 2011 hurricane season. This verified with the
landfall of Tropical Storm Lee on September 4 along the Louisiana Coast.
The secondary predictors in the index called for at least 10 named storms with 6 of
them intensifying into hurricanes. The 2011 season had 18 named storms, seven of
which intensified into hurricanes. There was an 80 percent chance that a Category 4
hurricane would form in the Atlantic and this verified with Hurricane Katia being a
Category 4 on September 5 and Hurricane Ophelia on October 2.
The outlook also gave a 60 percent chance of more than 5 tropical storms or hurricanes
making landfall somewhere along the U.S. Coast. Only three cyclones made landfall in
the U.S., with Tropical Storm Don making landfall in Texas, Hurricane Irene in North
Carolina and along the east Coast and Tropical Storm Lee in Louisiana.
2011 WRC OCSI FORECAST FOR THE ATLANTIC
COAST
Texas
Mexico
Louisiana to Alabama
West Florida
East Florida
Georgia to N. Carolina
East Coast of U.S.
WRC OCSI
70%
40%
CLIMATOLOGY
51%
40%
90%
90%
60%
70%
30%
59%
71%
41%
56%
36%
OBSERVED
TS Don
TS Arlene,
TS Harvey
TS Lee
Hur Irene
Hur Irene
Other 2011 Predictors from WRC’s OCSI
Number of Named Storms
Number Intensifying into Hurricanes
Number of Hurricane Days
Number of Tropical Storm Days
U.S. Landfalls
Category 3, 4 or 5 Storms in the Atlantic Basin
-more-
OCSI Forecast Observed
10
18
6
7
69
30
5
80%
Irene,
Katia, Ophelia
2
The 2011 Outlook indicated the Gulf of Mexico to be more active with the highest risk of
a tropical storm or hurricane landfall along the coast from Louisiana to West Florida.
This verified with the landfall of Tropical Storm Lee along the Louisiana Coast. The
coast of Texas and the coast from Georgia to North Carolina had the second highest
risk of a cyclone landfall with 70 percent. This verified with the landfall of Tropical Storm
Don on the Texas Coast and Hurricane Irene on the North Carolina Coast.
The index also called for a long season with June having a 60 percent chance of having
a tropical cyclone. Tropical Storm Arlene formed on June 29. November had a 30
percent chance of experiencing a tropical cyclone. This verified with Tropical Storm
Sean. There were three systems in July, seven in August, three in September, three in
October and one in November.
The most memorable hurricane of the season was Irene which moved up the east
coast. When you review the past years in this phase of the OCSI, it was not surprising.
Other years with significant east coast storms were the East Coast Hurricane of 1916,
East Coast Hurricane of 1947, Hurricane David in 1979, Hurricane Hugo in 1989 and
Hurricanes Dennis and Floyd in 1999.
About Weather Research Center and the Orbital Cyclone Strike Index
Houston-based Weather Research Center is one of a handful of organizations that
makes seasonal hurricane predictions. WRC uses a model called Orbital Cyclone Strike
Index (OCSI) which uses the solar cycle (an indication of the solar system’s orbit) to
predict the risk for coastal residents each hurricane season. The OCSI model is based
on the premise that there are orbital influences reflected in the global circulation pattern
on the sun as well as the global circulation pattern of the earth. These orbital influences
are reflected in the 11.1-year sun spot cycle.
In addition to its ongoing research, WRC also provides storm and hurricane information
via the Internet through Storm Navigator®. This service offers detailed storm updates
and related information. WRC’s current and past predictions can be found at
www.wxresearch.com/outlook.
Founded in 1987, the non-profit Weather Research Center manages a worldwide
forecasting operation and provides groundbreaking research to scientists around the
world. Meteorologists provide tropical cyclone advisories worldwide, severe weather
advisories, marine forecasts, long-range outlooks, environmental studies and forensic
meteorology services. WRC provides research into tropical cyclones as well as realtime weather forecasts. WRC can also provide you with an assessment of your severe
weather and tropical weather plans.
Jill F. Hasling, WRC President, is a Fellow and Certified Consulting Meteorologist from
the American Meteorological Society as well as a member of the National Council of
Industrial Meteorologists. For more information about Weather Research Center and
the John C. Freeman Weather Museum, please call (713) 529-3076 or visit
www.wxresearch.com.
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