1996 Atlantic Ocean Tropical Storms and Hurricanes

Introduction

U.S. eastern seaboard residents experienced a busy hurricane season in 1996. Following on the heels of the 1995 season in which 19 were named storms and 11 were hurricanes, 1996 saw 13 named storms of which 9 became hurricanes. Of these nine, six reached Category 3 or higher on the Saffir-Simpson Hurricane Scale. The Saffir-Simpson Scale is used to relate potential property damage and coastal flooding to hurricane intensity. For example, category three denotes a storm with sustained winds between 49.6 and 58 m/s (96 and 113 kn) with a storm surge of 1.8 to 2.4 m (6 to 8 ft).

The data measured and reported by NDBC moored and drifting buoys and C-MAN stations again were a valuable asset to hurricane forecasters and the public. NDBC stations directly measured and reported meteorological and oceanographic data in 7 of the 13 storms. Highlights and summaries of the data obtained in these storms are contained in this report. A complete description of the hurricane season is available electronically from the TPC via the WWW at http://www.tpc.noaa.gov.

Storm Summaries

Tropical Storm Arthur

A tropical wave originated off Puerto Rico and while moving north gained strength. It developed into a tropical depression east of Grand Bahama Island on June 17. The depression continued moving northward and passed near several NDBC stations on its way to hurricane development. On June 18, station 41009 reported sustained winds of 11.9 m/s (23.1 kn) with gusts of 14.3 m/s (27.8 kn). At 2300 UTC, station 41004 reported sustained wind speeds of 13.2 m/s (25.6 kn) with gusts of 16.2 m/s (31.4 kn).

The depression was named Arthur when just east of South Carolina on June 19. That day, Arthur passed over NDBC C-MAN station FPSN7. FPSN7 reported sustained wind speeds of 17.7 m/s (34.4 kn) with gusts to 20.3 m/s (39.4 kn). Arthur subsequently passed directly over CLKN7 on June 20, at 0000 UTC. At that time, CLKN7 reported wind speeds of 11.8 m/s (22.9 kn), gusts of 13.2 m/s (25.6 kn), and a minimum barometric pressure of 1005.9 hPa. On June 20, DSLN7 reported sustained winds of 19.1 m/s (37.1 kn). Although the most dangerous portion of the storm remained offshore, locally heavy rains were associated with the storm. After crossing the barrier islands of North Carolina, Arthur was steered east into the Atlantic by intense westerly winds.

Hurricane Bertha

Hurricane Bertha was a rare storm in that it was a strong hurricane in the early part of the hurricane season. In early July, a Cape Verde system (an array of clouds originating off the Cape Verde Islands) formed, traversed the Atlantic, grew in intensity, and eventually was named "Bertha."

NDBC buoys and C-MAN stations from Florida to Maine (a span of more than 1,000 nmi) reported meteorological and oceanographic data associated with Hurricane Bertha for 4 days. Station 41010 was the first NDBC site to measure data associated with Bertha: sustained winds of 18.1 m/s (35.3 kn), gusts to 22.8 m/s (44.3 kn), and a minimum pressure of 996 hPa. On July 12, station 41004 reported a minimum pressure of 998.2 hPa, maximum sustained wind speeds of 19.9 m/s (38.7 kn), and gusts to 25.4 m/s (49.3 kn). To the west of 41004, station FBIS1 reported speeds of 16.7 m/s (32.4 kn) with gusts to 19.9 m/s (38.7 kn). Also on July 12, FPSN7 reported wind speeds of 37.1 m/s (72.1 kn) with gusts of 45 m/s (87.4 kn). FPSN7 also reported a minimum pressure of 977.5 hPa.

Bertha made landfall on the beaches of North Carolina on July 12 causing flooding, beach erosion, fallen trees, and severe damage to roofs and piers. NDBC has three stations on the North Carolina coast (CLKN7, DUCN7, and DSLN7) that reported data. These data gave forecasters insight into the storm's intensity and movement. CLKN7 reported sustained wind speeds of 25.2 m/s (49.0 kn) with gusts to 31.9 m/s (62 kn). DUCN7 reported speeds of 21.9 m/s (42.5 kn) with gusts to 25.1 m/s (48.7 kn). DSLN7 reported a minimum pressure of 1007.1 hPa, sustained wind speeds of 30.2 m/s (58.7 kn), and gusts to 35 m/s (68.0 kn).

Bertha then continued northward through the mid-Atlantic states of Virginia and Maryland. The first NDBC station in Virginia to measure and transmit data from Bertha was CHLV2. On July 13, CHLV2 reported maximum winds of 25.1 m/s (48.8 kn) with gusts to 29.1 m/s (56.5 kn). A minimum pressure of 998.9 hPa was measured at 0800 UTC. The same pressure was measured at TPLM2. Buoys 44009 and 44014 recorded speeds in excess of 22 m/s (42.7 kn). Station 44009 recorded a minimum pressure of 997.1 hPa at 1400 UTC.

Bertha continued to curve toward the northeast, and data were measured and transmitted by NDBC stations ALSN6, 44025, and 44028. On July 13, ALSN6 reported a minimum pressure of 994.5 hPa, sustained winds of 22.8 m/s (44.2 kn), and gusts to 24.5 m/s (47.5 kn). Station 44025 reported a minimum pressure of 995.4 hPa, sustained winds of 16.9 m/s (32.8 kn), gusts to 21.3 m/s (41.4 kn), and a significant wave height of 5.5 m (18 ft). Station 44028 reported sustained winds of 18.5 m/s (35.9 kn), gusts to 22.4 m/s (43.5 kn), and a minimum pressure of 997.1 hPa.

Bertha traveled through the northeastern states, and data were measured and transmitted by three NDBC C-MAN stations: IOSN3, MISM1, and MDRM1. On July 13, IOSN3 reported maximum sustained wind speeds of 19 m/s (36.9 kn), maximum gusts to 23.2 m/s (45.1 kn), and a minimum pressure of 996.4 hPa. A few hours later, on July 14, MISM1 reported maximum wind speeds of 18.1 m/s (35.2 kn), gusts to 20.3 m/s (39.4 kn), and a minimum pressure of 995.3 hPa. MDRM1 reported maximum sustained wind speeds of 16.8 m/s (32.6 kn), gusts to 18.8 m/s (36.6 kn), and a minimum pressure of 995.3 hPa.

On July 14, Bertha was classified as extratropical. Extratropical means no longer having characteristics of tropical storms and includes reference to geographic position and the change in energy source. Although Bertha was no longer tropical, the storm greatly affected the east coast of Canada with winds in excess of 23.1 m/s (44.9 kn).

Hurricane Edouard

Edouard, also a Cape Verde low-pressure system, originated on August 19. Edouard moved westward and reached hurricane intensity on August 23. Station 41002 was the first NDBC station to provide data associated with this storm. On August 31, 41002 recorded a minimum pressure of 1008.5 hPa, a substantial change from its August climatological mean of 1018.0 hPa. On September 1, 41001 reported maximum sustained winds of 16.9 m/s (32.8 kn), gusts to 21.3 m/s (41.4 kn), and a minimum pressure of 1002.4 hPa. On September 2, station 44004 reported maximum sustained winds of 23.0 m/s (44.7 kn) and gusts to 21.0 m/s (40.8 kn). Later that day, 44004 reported a minimum pressure of 984.2 hPa. On September 2, 44008 transmitted maximum wind speeds of 19.9 m/s (38.7 kn), gusts to 25.9 m/s (50.2 kn), and a minimum pressure of 979.9 hPa. Station 44011 transmitted maximum wind speeds of 20.1 m/s (39.0 kn), gusts to 26.2 m/s (50.8 kn), and a minimum pressure of 986.8 hPa. Although Edouard turned toward the east and weakened to tropical storm strength, NDBC stations IOSN3, 44007, MISM1, and MDRM1 reported pressures of approximately 1005 hPa, a departure from their August climatological mean of approximately 1018 hPa.

Edouard was the strongest storm of the 1996 Atlantic Hurricane Season. It maintained its Category 3 status for 8 days. Damage associated with Edouard included beach erosion due to large swells, coastal flooding and wind damage, as well as two deaths.

Hurricane Fran

Hurricane Fran was another Cape Verde hurricane that made landfall along the east coast. Fran first became a hurricane on August 29 in the tropical Atlantic near 16 N., 55 W. NDBC moored buoys, C-MAN stations, and drifting buoys were instrumental in providing real-time data to forecasters and the public as Fran moved toward the United States.

NDBC deployed an array of drifting buoys in the tropical Atlantic Ocean specifically to assist in data gathering during the 1996 Hurricane Season. NDBC drifting buoys 41527, 41529, and 41530, situated near 31 N., 77 W., provided much needed offshore data about the intensity of Hurricane Fran. The eye of Fran passed very close to drifting buoy 41529 on September 5. Station 41529 reported maximum sustained wind speeds of 25 m/s (48.6 kn), gusts to 32 m/s (62.2 kn), and a minimum pressure of 954 hPa. These three drifting buoys survived the harsh conditions associated with Fran and continued to measure and transmit data. In fact, one of them was voluntarily retrieved later in 1996, and the other two were still operational as of March 1997.

As Fran moved toward the east coast, many NDBC stations provided data in real time. On September 5, station 41002 reported maximum sustained wind speeds of 19.0 m/s (36.9 kn), gusts to 25.7 m/s (49.9 kn), and a minimum pressure of 1000.3 hPa. Station FBIS1 reported a minimum pressure of 997.6 hPa. At 1900 UTC, station 41004 reported maximum sustained wind speeds of 24.4 m/s (47.4 kn), gusts to 32.6 m/s (63.3 kn), and a minimum pressure of 988.7 hPa. This was the last transmission from station 41004 as the severe conditions associated with the storm caused the buoy to break free of its mooring and capsize.

As Fran made landfall as a Category 3 storm in extreme southern North Carolina, NDBC C-MAN stations to the north of the storm reported data hourly. Station FPSN7 reported maximum sustained wind speeds of 40.8 m/s (79.2 kn), gusts to 48.6 m/s (94.4 kn), and a minimum pressure of 960.6 hPa. On September 6, CLKN7 reported maximum sustained wind speeds of 29.0 m/s (56.3 kn), gusts to 34.3 m/s (66.6 kn), and a minimum pressure of 996.9 hPa. DSLN7 reported maximum sustained wind speeds of 29.8 m/s (57.9 kn), gusts to 33.3 m/s (64.7 kn), and a maximum pressure of 1006.6 hPa. DUCN7 also reported sustained wind speeds in excess of 20 m/s (38.9 kn). Significant wind damage and flooding were reported along the North Carolina coast. Fran continued moving inland and brought wind damage and severe flooding to Virginia, West Virginia, Maryland, Ohio, and Pennsylvania. Total U.S. damages are estimated at more than $3.2 billion.

Hurricane Isidore

Although Hurricane Isidore was never a threat to any landmass, NDBC drifting buoys provided valuable data for hurricane forecasters and research scientists. According to the TPC, formerly called the NHC, the eastern end of the NDBC drifting buoy array provided valuable data concerning the structure and intensity of the western part of Isidore's low-level wind field.

Tropical Storm Josephine

A cluster of showers originated over the southwestern Gulf of Mexico. On October 6, Josephine was classified as a tropical storm. At that time, station 42002 reported maximum sustained winds of 21.0 m/s (40.7 kn), gusts to 27.4 m/s (53.2 kn), and a minimum pressure of 1001.2 hPa. As Josephine moved eastward, station 42001 reported a minimum pressure of 997.0 hPa on October 7, at 0700 UTC.

Josephine then turned toward the Florida panhandle. Station 42003 reported maximum sustained wind speeds of 20.6 m/s (40.0 kn), gusts to 25.7 m/s (49.9 kn), and a minimum pressure of 996.1 hPa. Station 42039 reported maximum sustained winds of 21.5 m/s (41.8 kn), gusts to 26.2 m/s (50.9 kn), and a minimum pressure of 989.5 hPa. Station 42036 reported maximum sustained winds of 20.9 m/s (40.5 kn), gusts to 25.2 m/s (49.0 kn), and a minimum pressure of 984 hPa.

Josephine made landfall in Taylor County, FL, on October 8, at 0330 UTC, with a central pressure of 983 hPa and wind speeds of 30 m/s (58.3 kn). At 0200 UTC, station CDRF1 reported maximum sustained wind speeds of 17.9 m/s (34.8 kn), gusts to 21.9 m/s (42.5 kn), and a minimum pressure of 992.6 hPa. At that time, station KTNF1 reported maximum sustained winds of 12.8 m/s (24.9 kn), gusts to 14 m/s (27.2 kn), and a minimum pressure of 989.2 hPa. As Josephine made landfall, KTNF1 missed only one hourly transmission. To the far west of landfall, station CSBF1 reported a minimum pressure of 993.7 hPa on October 7, at 2300 UTC.

As Josephine entered Florida, she was beginning to lose her tropical characteristics and was classified as extratropical. NDBC stations continued to measure and transmit data to the meteorological community and the public. Table 1 shows some extremes measured by NDBC stations as the extratropical storm traversed along the east coast. Storm surge associated with Josephine ranged from 0.9 to 1.2 m (3 to 4 ft) along the Florida coast. As a result, extensive flooding occurred. Rainfall was estimated to be as much as 23 cm (9 in) in some Florida locations.

Hurricane Lili

Hurricane Lili was a late-season storm that, thankfully, spared the United States. Central America and the Caribbean Islands were not as lucky, however. The Category 3 Lili caused great hardship in several nations including the Bahamas, Cuba, Nicaragua, Honduras, and Costa Rica resulting from severe flooding and wind damage. Thousands were left homeless.

As Lili skirted around the southern United States, the various NDBC C-MAN stations in the Florida Keys measured and transmitted hourly data. On October 18, SANF1 reported maximum winds of 14.1 m/s (27.4 kn), gusts to 15.5 m/s (30.1 kn), and a minimum pressure of 1003.5 hPa. SMKF1 reported similar data. DRYF1 reported maximum sustained speeds of 11.1 m/s (21.6 kn), gusts to 13.3 m/s (25.8 kn), and a minimum pressure of 1005.4 hPa. MLRF1 reported a minimum pressure of 1003.1 hPa with gusts to 14.0 m/s (27.2 kn) on October 19.

Postcalibration Results

NDBC performs predeployment calibration tests on the meteorological and oceanographic sensors installed at all NDBC stations. For special situations, such as when an NDBC station has encountered a hurricane, NDBC performs postdeployment calibration testing. The following subsections document both the performance and pre- and postcalibration results of the two wind sensors, air temperature sensor, and barometer removed from FPSN7 on November 6, 1996. For convenience and clarity, the pre- and postdeployment calibration results are presented in Tables 2 through 7.

Hurricane Performance

Two hurricanes passed close to FPSN7 during the 1996 Atlantic Ocean Hurricane Season. On July 12, Hurricane Bertha passed near FPSN7. Throughout the storm, FPSN7 transmitted data hourly without any missed transmissions of meteorological data (Figure 1). The barometer measured air pressures as low as 977 hPa while the anemometer measured 2-minute averaged wind speeds of 35 m/s (68 kn) and 5-s gusts of 45 m/s (87.4 kn).

Hurricane Fran passed over FPSN7 on September 5. FPSN7 only missed two hourly reports of barometric pressure during this storm. The lowest barometric pressure recorded by FPSN7 during Fran was 960.6 hPa. The highest reported 2-minute averaged wind speed reported during Fran by FPSN7 was 40.8 m/s (79.3 kn) with gusts to 48.6 m/s (94.4 kn).

Calibration Results

Predeployment calibration results show all sensors were within specification, a requirement for subsequent installation. NDBC requires a difference of no more than 5 degrees, 1.0 m/s, 0.75 hPa, and 1.0 degree C for wind direction, wind speed, barometric pressure, and air temperature measurements, respectively, to pass either a pre- or a postdeployment calibration test.

Generally, the FPSN7 postdeployment results compare favorably with the FPSN7 predeployment results. However, a few failures did occur. Postdeployment calibration results show the failure of wind sensor #1 at speeds greater than 20 m/s, the failure of wind sensor #2 at all speed ranges, and a failure of the barometer at environmental temperatures of -10 degrees C and 40 degrees C.

Young Wind Sensor #1 (SN 16187)

Wind sensor #1 was installed August 31, 1994, and was removed November 6, 1996. This sensor remained onboard the station for 797 days. Postdeployment calibration shows the failure of the wind speeds above 20 m/s by +8 percent.

Postdeployment testing also shows the wind directions to differ from the standard by a maximum of 4.0 degrees. However, this statistic is within NDBC's calibration limit for wind direction of 5.0 degrees; therefore, this sensor passed the calibration test for wind direction.

R.M. Young Wind Sensor #2 (SN 4044)

Wind sensor #2 was installed May 24, 1995, and was removed November 6, 1996. This sensor remained onboard for 531 days. Postdeployment calibration testing shows the failure of wind speeds for all speeds. Wind speeds measured by this sensor were low by a maximum of 13 percent. This is consistent with the discrepancy report (SDR 960214) written June 18, 1996, stating the wind speeds were 10 to 15 percent low.

Wind direction measurements from this sensor passed postdeployment calibration. Postdeployment testing of wind direction shows the sensor to differ from the standard by a maximum of 3.0 degrees, again well within NDBC's calibration limit.

Air Temperature (SN 004)

The air temperature sensor was installed August 11, 1993, and was removed November 6, 1996, being onboard for 1,182 days. A discrepancy report was written February 6, 1996 documenting the suspected low values measured by this sensor. However, this sensor passed the postdeployment calibration testing for all temperature ranges within -35.55 degrees C through 34.18 degrees C. The results of the postdeployment test are similar to those of the predeployment test.

Barometer (SN 077)

Barometer 077 was installed October 14, 1993, and was removed November 6, 1996. This sensor was onboard for 1,118 days. Postdeployment calibration shows the sensor failing the 0.75-hPa limit at environmental temperatures of -10 degrees C and 40 degrees C. Note the maximum deviation at these two temperatures was 0.94 and 0.76 hPa, respectively. The test performed at an environmental temperature of 40 degrees C came very close to passing.

Postcalibration Conclusion

FPSN7, like other NDBC stations, is an invaluable source of real-time meteorological and oceanographic data. NDBC data are used by forecasters, research scientists, engineers, boaters, and others who have a professional and/or a recreational interest in marine data.

Through its predeployment calibration testing, NDBC ensures the instruments placed onboard buoys and C-MAN sites accurately measure the parameters of the marine environment. Many of these sensors, such as those placed onboard FPSN7, operate for more than 800 days. Postdeployment testing of these sensors enable NDBC to quality control further the data measured by these sensors. Sensor flaws and errors uncovered by postdeployment testing can motivate the development of improved sensors for future use.

FPSN7 has provided marine data since 1984. In its most recent past, FPSN7 survived two Atlantic Ocean hurricanes within 3 months. Many sensors onboard FPSN7 endured the harsh environmental conditions for more than 2 years and still passed rigorous postdeployment calibration testing.

Conclusion

The 1996 Atlantic Ocean Hurricane Season was very active. NDBC moored buoys, C-MAN stations, and drifting buoys greatly contributed to the accurate monitoring, forecasting, and study of these storms. Postdeployment calibration of sensors shows the reliability of NDBC sensors and data, even after the passage of two hurricanes.

Glossary

ASLN6 Ambrose Light, NY
CDRF1 Cedar Key, FL
CHLV2 Chesapeake Light, VA
CLKN7 Cape Lookout, NC
C-MAN Coastal-Marine Automated Network
CSBF1 Cape San Blas, FL
DRYF1 Dry Tortugas, FL
DSLN7 Diamond Shoals, NC
DUCN7 Duck, NC
FBIS1 Folly Beach, SC
FPSN7 Frying Pan Shoals, NC
IOSN3 Isle of Shoals, NH
KTNF1 Keaton Beach, FL
MDRM1 Mount Desert Rock, ME
MISM1 Matinicus Rock, ME
MLRF1 Molasses Reef, FL
NDBC National Data Buoy Center
NHC National Hurricane Center
SANF1 Sand Key, FL
SDR Station Discrepancy Report
SMRF1 Sombrero Key, FL
TPC Tropical Prediction Center
TPLM2 Thomas Point, MD