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Development
and Impacts –
Hurricane Bertha formed from a tropical wave that moved
off the coast of Africa on July 1st. By 8 p.m. July 5th, satellite
imagery indicated the storm had developed into a Tropical Depression. Soon after, the depression would be
upgraded to a Tropical Storm by 8 a.m. July 6th, progressing
quickly on a west-northwesterly track at about 23-29 mph. For the next few days, the storm
continued on this path, steered by a strong Atlantic high pressure system
located over the central Atlantic.
During this time, the storm underwent gradual intensification and by
2 p.m. on the 7th, the Tropical Storm was upgraded to Hurricane status with
maximum sustained winds of 75 knots (86 mph).
The first of many places to feel the impact of Hurricane
Bertha would be the Leeward and Virgin Islands. The center moved between Antigua and
Barbuda on 2 a.m. July 8th and eventually across St. Martin,
just north of St. Thomas, and over the British Virgin Islands by 2 p.m. on
the same day. These areas
observed hurricane conditions resulting in moderate to severe damage. Boats were destroyed, homes were
damaged, and one man suffered injuries from riding out the storm in his
sailboat. Total damages were
estimated around $7.5 million.
As the storm continued on, the track turned to a slower
more northwesterly path, moving around 17-22 mph. Bertha experienced a period of rapid
intensification while it was located 138 miles north of Puerto Rico. At 2 a.m.
July 9th, the hurricane reached its peak intensity. The maximum sustained wind speeds
were 100 knots (115 mph) with a minimum pressure of 960 mb, making Bertha a
Category 3 hurricane for a brief period. Considering the strongest part of
the hurricane was in the northeast quadrant, Puerto Rico only suffered
Tropical Storm conditions. General rainfall amounts averaged 1-3 inches
with and isolated maximum of 6.89 inches located on the northeast corner of
Puerto Rico.
The hurricane weakened for another brief period as it
turned more north-northwesterly, paralleling the Bahamas, and slowing its
course to about 9 mph over the 10th and 11th. Wind
speeds decreased to Category 1 status (74-95 mph) as the storm continued
moving north-northwest parallel to the Florida and Georgia coastlines,
remaining 170-200 miles off shore Fig. 3.
Figure 3. July 11th,
11:15 a.m. Bertha as a Category 1 storm before undergoing a period of rapid
intensification. (NCDC)
As the center of the storm approached the South Carolina
coast, the track turned more north-northeast and accelerated to about 17
mph. As the storm headed for
the North Carolina coast, Bertha underwent another period of rapid
intensification just 12 hours before landfall. The storm’s wind speeds went
from a Category 1 status to Category 2, with maximum sustained wind speeds
of 104 mph (Fig. 4).
Figure 4. July 12th,
12:15 p.m. Bertha as a Category 2 storm four hours before landfall. Much better organization after rapid
intensification from crossing the Gulf Stream. (NCDC)
At 4 p.m. July 12th, Hurricane Bertha finally
made landfall between Wrightsville and Topsail Beaches in North
Carolina. Maximum sustained
winds were 90 knots (104 mph) with a minimum pressure of 974 mb at
landfall. Hurricane Bertha
quickly lost strength after it made landfall and continued moving northeast
along the US coast. Forty to
fifty knot sustained winds were reported over land from northern North
Carolina to New England. By 8
a.m. July 14th the system was declared extratropical and was
tracked until 8 p.m. July 16th where it had passed Greenland.
Although Hurricane Bertha caused damage from the Virgin
Islands to Puerto Rico and from Florida all the way up through New England,
the most extensive damage occurred in North Carolina. Twelve deaths total were reported to
be related in some way to Bertha.
Two of those were in North Carolina where one death was from a car
accident and the other had drowned in rip currents. The Virgin Islands and North
Carolina were declared federal disaster areas and there were 750,000 people
evacuated in North Carolina alone.
Rainfall totals throughout eastern NC varied from 1-7 inches. Heavier accumulations reported
towards the coastline where totals ranged from 3-5 inches with isolated
reports of 7+ inches. The maximum
rainfall measured was 9.20 inches located at Southport 5N, NC (Fig.
5). Majority of the damage in
coastal North Carolina was a result of coastal flooding. Coastal storm surge ranged from 1-4
ft. from Florida to New England, with reported values of up to 5 ft. in
North Carolina. A storm surge
of 6 ft. was indicated near Swansboro, NC. Coastal erosion was prevalent along
the coast, specifically to beach dunes and coastal roads. The sand dunes in Emerald Isle had
8-10 ft. vertical drops. Fifty feet of land was washed away from Mason
Inlet. Numerous houses were
damaged not only from strong winds, but also from beach erosion.
Figure 5.
Rainfall totals from Bertha (HPC)
Agricultural damage was extensive due to long exposure
to the Northeast winds before landfall, with damage cost in just three
counties alone estimated to be $21 million. The highest wind gust reported on
land occurred at Camp Lejeune in Jacksonville, NC at a speed of 108
mph. The most intense wind
damage was located between North Topsail Beach and Emerald Isle, NC. Initially there were six reports of
tornado touchdowns in Eastern NC.
However, during an aerial survey, it was determined that only one
report could be verified. The
track was identified from this survey and was estimated to last 1.5 miles
and rated as an F-1 tornado.
Most of the damage in Virginia was a result of tornadic storms
associated with Bertha. Rainfall totals in coastal Virginia and Maryland
Shores ranged from 3-6 inches with 2-4 inches reported throughout inland
Virginia. The western shore of
the Chesapeake Bay reported 4-4.5 inches while inland Maryland/D.C. area
only had amounts in the 1-2.5 range.
Coastal Jersey generally reported 2-4 inches with isolated reports
of 6+ inches. Coastal New York
claimed 1-3 inches with isolated reports of 4+ inches. The New England area generally had
2-4 inches with isolated reports of 5+ inches. Most of the coast from Virginia to
New England only suffered minor coastal flooding. Between North Carolina, Virginia,
and South Carolina, the American Insurance Association reports an estimated
$135 million in insured property losses, with the majority being $100
million in North Carolina.
Figure 6. MHX
Radar image one hour after landfall (NCDC)
The path of destruction left by Hurricane Bertha was devastating. It left thousands without power for
several days up and down the east coast, cost millions of dollars in
damage, claimed twelve lives, nearly washed away dunes and piers, and
robbed the tourist industry of millions of dollars. Hurricane Bertha was the first of
four significant hurricanes that would make landfall in the late
1990’s.
Sources-
NCDC
Bertha Images
NCDC
Bertha Discussion
Wikipedia
National Hurricane Center
Monthly Weather
Review
HPC
Coastal Services Center
NWS Service
Assessment
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