As the 2007 Atlantic hurricane season officially comes to a
close on November 30, NOAA scientists are carefully
reviewing a set of dynamic weather patterns that yielded
lower-than-expected hurricane activity across the Atlantic
Basin. As a result, the United States was largely spared
from significant landfalling storms. However several
noteworthy events took place, including two back-to-back
Category 5 hurricanes hitting Central America and the rapid
near-shore intensification of the single U.S. landfalling
hurricane.
May
Subtropical Storm Andrea developed off the southeastern
coast of the United States on May 9 prior to start of the
official Atlantic hurricane season (June 1), becoming the
first named storm in May since 1981. Andrea had maximum
sustained winds of 50 mph (43 knots) and immediately
weakened to a depression on May 10. Storms that occur prior
to the official start of the hurricane season are not
uncommon. As recently as 2003, a tropical storm developed
earlier in the season when Tropical Storm Ana formed on
April 22.
June
Tropical Storm Barry developed in the southeastern Gulf of
Mexico on June 1. Peak intensity was 60 mph (52 knots) with
a minimum pressure of 997 mb. Beneficial rains fell in parts
of Florida and Georgia.
The development of two named storms prior to the end of June
is not an unusual occurrence. The 2007 season was the 23rd
season since Atlantic Basin records began in 1851 that two
or more named storms formed prior to the end of June.
July
On July, an area of low pressure developed near the
Bahamas and tracked to the north-northeast. As it organized,
it was upgraded to a tropical depression late on July 30. By
July 31, the system strengthened into Tropical Storm Chantal
south of Nova Scotia. It became extratropical late that same
day as it moved over the cool waters of the north Atlantic
towards Newfoundland. Peak intensity was 50 mph (43 knots)
with a minimum pressure of 994 mb.
Tropical cyclone activity in the Atlantic Basin during
July was near average with one tropical storm.
August
On August 13, Tropical Depression Four formed in the
eastern Atlantic Ocean off the coast of Africa. This
tropical depression became organized as it moved west and
was upgraded to Tropical Storm Dean. As Dean progressed
westward, it continued to intensify and was classified as
the first 2007 Atlantic hurricane on August 16. The
hurricane passed into the Caribbean near Martinique and
Saint Lucia as a Category 2 hurricane on August 17.
Dean continued to strengthen and reached Category 5
status by late on August 20, and it made landfall as a
Category 5 hurricane on August 21 on the Yucatan Peninsula
of Mexico near Costa Maya in a sparsely populated area.
After weakening over the peninsula, Dean passed again over
open water in the southwestern part of the Gulf of Mexico,
enabling it to strengthen back to a Category 2 hurricane
before making landfall a second time near Tecolutla on
August 22. Peak intensity was 165 mph (144 knots) with a
minimum pressure of 906 mb. Dean was responsible for roughly
40 deaths and major damage across the southern and central
Caribbean with the largest tolls in Mexico and Haiti.
A tropical depression formed on August 14 about 425 miles
east-southeast of Brownsville, Texas, and about 425 miles
east of La Pesca, Mexico. It organized enough to be
classified the next day as a tropical storm and given the
name Erin. Erin weakened and crossed the Texas coast near
Lamar on August 16 as a tropical storm and later became
extratropical. The remnants of Erin continued northwestward
through Texas and turned north and tracked over the
south-central U.S., causing extensive flooding in Oklahoma
on August 19. Peak intensity was 40 mph (35 knots) with a
minimum pressure of 1003 mb.
On August 31, a westward-moving tropical depression
formed east of the Windward Islands. It organized enough to
be classified the next day as Tropical Storm Felix and
intensified later that day into a hurricane.
Three tropical cyclones formed in the Atlantic Basin
during August. Two of these cyclones became named storms and
one of these, Dean, reached major hurricane status. The
number of tropical storms and hurricanes was slightly below
average for August.
September
Hurricane Felix continued to move westward over very warm
waters and intensified into a Category 5 storm by late on
September 2. Felix weakened briefly overnight and then
strengthened into a Category 5 storm again before it struck
northeastern Nicaragua on September 4. The rugged terrain of
Central America weakened the storm significantly such that
it was downgraded to a tropical depression on September 5.
The strongest winds in Hurricane Felix were 165 mph (144
knots), and its lowest pressure was 929 mb.
Media reports indicate that Felix was responsible for
more than 100 deaths in Nicaragua and Honduras. The
hurricane caused major damage in the landfall area in
Northeastern Nicaragua with many buildings damaged or
destroyed along the coast near and north of Puerto Cabezas.
Additional significant damage occurred due to inland
flooding over portions of Central America. Felix also
produced minor damage on Grenada, Aruba, Bonaire, and
Curacao. An area of low pressure off the Carolina coast
developed into Subtropical Storm Gabrielle on September 7.
Reconnaissance aircraft data suggested the presence of a
weak warm core on the 8th, prompting a reclassification of
Gabrielle as a tropical storm. The system passed over the
Outer Banks of North Carolina on the ninth, and weakened to
a depression the next day as it moved northeast. The final
advisory was issued on September 11. The strongest winds in
Tropical Storm Gabrielle were 50 mph (44 knots), and its
lowest pressure was 1004 mb.
Hurricane Humberto began as an area of disorganized
showers and thunderstorms off the coast of western Cuba on
September 8. These storms moved slowly west-northwestward
across the Gulf of Mexico and organized enough to be
classified as Tropical Depression Nine on the morning of
September 12. Within a few hours, the tropical depression
had strengthened into Tropical Storm Humberto. The system
turned northward and continued to intensify until it reached
hurricane status early in the morning of September 13.
Hurricane Humberto made landfall near High Island, Texas, as
a Category 1 hurricane. The storm rapidly weakened as it
traveled northeast over land and dropped heavy amounts of
rain on Louisiana, Mississippi, Alabama, and parts of
Georgia and the Carolinas. Humberto is blamed for the death
of a man who was killed by a falling carport in Bridge City,
Texas. The strongest winds in Hurricane Humberto were 85 mph
(73 knots), and its lowest pressure was 986 mb.
A tropical wave 1,130 miles east of the Lesser Antilles
developed into Tropical Depression Eight on September 12 at
the same time that the system that later became Humberto
developed. Unlike Tropical Depression Nine, this depression
developed slowly and did not become Tropical Storm Ingrid
until September 14. Ingrid was weakened by strong
upper-level winds and reclassified as a depression on
September 15. The storm continued to grow increasingly
disorganized and the final advisory was issued on September
17. The strongest winds in Tropical Storm Ingrid were 45 mph
(40 knots), and its lowest pressure was 1004 mb.
Tropical Depression Ten formed in part from a decaying
frontal boundary that became stationary off the Southeast
Coast on September 17. On September 18 an upper-level low
formed over Florida and the eastern Gulf of Mexico while a
westward-moving wave was moving over the Bahamas. These
features combined to produce a weak area of low pressure
over the western Bahamas later that day. This system moved
slowly westward over Florida and into the eastern Gulf
September 19-20. On September 21 thunderstorm activity
increased near the surface low and a subtropical depression
formed about 45 miles southwest of Apalachicola, Florida.
This system was reclassified as tropical depression as it
moved northwestward, but it maximum winds never exceeded 35
mph. Tropical Depression Ten made landfall near Fort Walton
Beach, Florida, and dissipated with minimal impacts.
In the early morning of September 23, an extratropical
area of low pressure was classified as a subtropical
depression about 1,060 miles west of the Azores. This
depression quickly strengthened into Subtropical Storm Jerry
later that morning and was reclassified as a tropical storm
early on September 24. Tropical Storm Jerry weakened later
on September 24 as it moved over cooler waters, then
re-intensified back into a tropical storm later that day
before being absorbed by a vigorous extratropical cyclone.
The strongest winds in Tropical Storm Jerry were 40 mph (35
knots), and its lowest pressure was 1000 mb.
Karen began as a very large tropical wave off the coast
of Africa that slowly organized into a tropical depression
on September 25. Later that same day, the storm strengthened
into Tropical Storm Karen. The strongest winds in Tropical
Storm Karen originally were estimated at 70 mph (60 knots),
and its lowest pressure was 990 mb. But post-storm analysis
found the winds were stronger than originally thought --- 75
mph (65 knots). So the National Hurricane Service upgraded
Karen to a hurricane two months after the storm ended. The
storm never threatened land and dissipated just east of the
Leeward Islands.
An area of convection that had been moving about the
western Caribbean was classified as a tropical depression on
the evening of September 25. The system moved slowly south
and southwest into the Bay of Campeche and intensified
rapidly on September 27 to Tropical Storm Lorenzo. The
system reached hurricane status early that evening and made
landfall in central Mexico the next morning as a Category 1
hurricane. The strongest winds in Hurricane Lorenzo were 80
mph (70 knots), and its lowest pressure was 990 mb.
On September 28, an area of low pressure near the Cape
Verde islands developed into a tropical depression. This
storm strengthened the next morning and became Tropical
Storm Melissa. The storm weakened into a tropical depression
and then a remnant low on September 30. The strongest winds
in Tropical Storm Melissa were 45 mph (40 knots), and its
lowest pressure was 1003 mb.
Eight tropical storms formed in the Atlantic Basin during
September. This tied 2002 for the record of the most
formations during the month. Four of the storms became
hurricanes, but only one of these became a major hurricane.
Although the number of tropical storms and hurricanes was
above average for September, most of these tropical cyclones
were relatively short-lived.
October-November
Tropical Depression Fifteen formed in the middle Atlantic
on October 11 about 860 miles east of Bermuda. The tropical
depression would last into October 12 then quickly diminish
to a remnant low as upper level wind shear tore the system
apart with little impact to any land 905 miles east of
Bermuda.
Tropical Storm Noel formed from a tropical wave that
departed the West Coast of Africa on October 16. As this
wave approached the Lesser Antilles, it began to interact
with an upper-level trough located near Puerto Rico. This
interaction lead to the formation of a broad surface low
pressure area on October 23 about 150 miles east-northeast
of the northern Leeward Islands. After forming, the low
moved slowly westward to west-southwestward during the next
couple of days with excessive heavy rain from Puerto Rico to
Hispaniola (Haiti and The Dominican Republic) to Cuba. Major
flooding would ensue from this storm. Strong upper-level
westerly winds that initially inhibited additional
development of the low decreased on October 27. This
resulted in the formation of a tropical depression early on
October 28 about 200 miles south of Port au Prince, Haiti.
The depression turned northwestward and strengthened to a
tropical storm shortly thereafter. Flooding rains continued
to swamp Hispaniola and Cuba. A tragic story was unfolding
with many homes and villages being flooded and reports of
many killed in the deluges. The maximum winds increased to
60 mph before Noel made landfall along the south coast of
Haiti early on October 29. The low-level circulation of Noel
became disrupted over Haiti and the center reformed near the
northwestern coast of Hispaniola a few hours later. After
the center re-formed, Noel tracked westward and made another
landfall in eastern Cuba early on October 30. Noel spent a
little more than 24 hours over eastern Cuba before emerging
over the Atlantic waters on October 31.
At the month's end, Noel was centered between Cuba and
the Bahamas, about 160 miles south-southwest of Nassau. Noel
would go down as one of the deadliest storms in the 2007
Atlantic Tropical Season due to mudslides and flash flooding
across The Dominican Republic and Haiti. Media reports said
143 people were killed because of Noel, making it the
deadliest storm for the season.
Noel's story would not end here as it would continue its
historical trek into November, becoming the season's fifth
hurricane. It pushed away from Cuba and became a minimal
hurricane on November 1. It reached a maximum wind of 80 mph
with a central pressure of 980 mb.
Noel then transitioned to an extratropial low pressure
center and dramatically deepened to 966 mb as it raced along
the eastern Seaboard. The lowest pressure would come in the
Maritimes. The winds expanded and slammed eastern Long
Island to eastern New England with wind gusts 50-90 mph. The
highest winds came offshore and over the outer Cape.
Considerable tree and power line damage was done in eastern
New England before the storm spun into the Maritimes as a
signifcant storm with wind gusts of 60-100+ mph. One gust in
the Maritimes reached 112 mph in Nova Scotia.
Quite a storm with serious impacts in the Caribbean due
to deadly flash flooding, Heavy beach erosion along the east
coast of Florida, and Northeast to Maritimes with tree and
power line damage.
Averages
The recent average seasonal activity (1995-2006) in the
North Atlantic basin is 14.8 named storms, 8.2 hurricanes
and 3.9 major hurricanes. These values represent an increase
over the average of the preceding 25 years (1970-1994) of
8.6 named storms, 5 hurricanes and 1.5 major hurricanes.
The 2007 Atlantic Basin season as of November 28, 2007,
had two tropical depressions, 14 named storms, six
hurricanes and two major hurricanes, slightly below average
for named storms and below average for hurricanes and major
hurricanes versus the recent average (1995-2006), but above
the long-term Atlantic Basin 25-year average for named
storms and near average for hurricanes and major hurricanes.
All in all, one hurricane, one tropical storm and three
tropical depressions struck the United States: Tropical
Depression Barry came ashore near Tampa Bay, Fla., on June
2; Tropical Depression Erin hit southeast Texas on August 16
and Tropical Depression Ten came ashore along the western
Florida panhandle on Sept. 21; Tropical Storm Gabrielle hit
east-central North Carolina on Sept. 9, and Hurricane
Humberto hit the upper Texas coast on Sept. 13.
Also this year, the U.S. was reminded of the dangers of
inland flooding. "Texas and Oklahoma experienced deadly
flooding when Erin dumped up to 11 inches of rain. Fresh
water flooding is yet another deadly aspect of tropical
cyclones," said Ed Rappaport, acting director of NOAA's
National Hurricane Center.
Eight storms formed in the Atlantic Basin during
September - tying September 2002 for having the most storm
formations during any given month.
For the first time in recorded history, two Category 5
hurricanes made landfall in the Atlantic Basin during the
same season. Hurricane Dean hit the Yucatan Peninsula near
Costa Maya on Aug. 21 with 165 mph winds, followed by
Hurricane Felix on Sept. 2, near Punta Gorda, Nicaragua,
with 160 mph winds. With a central pressure of 906 millibars,
Hurricane Dean had the third lowest pressure at landfall --
behind the Labor Day 1935 Hurricane in the Florida Keys and
Hurricane Gilbert of 1988 in Cancun, Mexico. Dean is also
the first Category 5 hurricane to make landfall in the
Atlantic Basin since Hurricane Andrew hit South Florida in
1992.
Hurricane Humberto grew from a tropical depression with
top winds of 35 mph into a hurricane with winds of 85 mph
within 24 hours - only three others storms (Celia 1970,
Arlene and Flora 1963) intensified faster during a 24-hour
period from below tropical storm strength.
The 2007 Atlantic hurricane season produced the predicted
number of named storms, but the combined number, duration
and intensity of the hurricanes did not meet expectations,"
said Gerry Bell, Ph.D., lead seasonal hurricane forecaster
at NOAA's Climate Prediction Center. "The United States was
fortunate this year to have fewer strong hurricanes develop
than predicted. Normally, the climate patterns that were in
place produce an active, volatile hurricane season."
The climate patterns predicted for the 2007 hurricane
season -- an ongoing multi-decadal signal (the set of
oceanic and atmospheric conditions that have spawned
increased Atlantic hurricane activity since 1995) and La
Ni#a -- produced the expected below-normal hurricane
activity over the eastern and central Pacific regions.
However, La Ni#a's impact over the Atlantic was weaker than
expected, which resulted in stronger upper-level winds and
increased wind shear over the Caribbean Sea during the peak
months of the season (August-October). This limited Atlantic
hurricane formation during that period. NOAA's scientists
are investigating possible climate factors that may have led
to this lower-than-expected activity.
Information and data from:
The Weather Channel
National Hurricane Center -- NOAA
National Climatic Data Center -- NOAA
Climate Prediction Center -- NOAA
Colorado State University -- Philip J. Klotzbach and William
M. Gray
The
2007 Atlantic hurricane season got off to an early start
with Subtropical Storm Andrea forming in early May. It
impacted the East Coast from North Carolina to Florida with
high waves, beach erosion and strong winds, but overall,
little rain for the drought-stricken Southeast.
NOAA
officials stress they can not predict how many hurricanes
will make landfall or where. But NOAA administrator Vice
Admiral Conrad C. Lautenbacher, Jr., USN (Ret.) said, "It
takes just one hurricane to make it a bad year."
