September 6-18, 2005
South Carolina Department of Natural Resources
Land, Water andConservation Division
South Carolina State Climatology Office
Compiled by Mark Malsick
List of Figures:
- Figure 1. Tropical Depression 16L north of the Bahamas. TD16L later strengthened to become Hurricane Ophelia.
- Figure 2. Tropical Storm Ophelia (45 knots, 1000 millibar central pressure).
- Figure 3. Early model track forecasts for Tropical Storm Ophelia, September 8, 2005.
- Figure 4. Hurricane Ophelia (65 knots, 990 millibar central pressure).
- Figure 5. Model track forecasts for Tropical Storm Ophelia on September 9, 2005.
- Figure 6. NHC forecast track issued September 10, 2005.
- Figure 7. Hurricane Ophelia.
- Figure 8. Tropical Storm Ophelia (60 knots, 976 millibar central pressure).
- Figure 9. Hurricane Ophelia's meandering track and problematic intensity changes over the Gulf Stream.
- Figure 10. Tropical Storm Ophelia (60 knots, 989 millibar central pressure).
- Figure 11. Wilmington, North Carolina, based National Weather Service Doppler radar image of Hurricane Ophelia.
- Figure 12. Surface pressure 12Z, September 10, 2005.
- Figure 13. 200 millibar geopotential height 12Z, September 10, 2005.
- Figure 14. Surface Synoptic chart, September 12, 2005 (Courtesy NOAA HPC)
- Figure 15. Surface Synoptic Chart, September 14, 2005 (Courtesy NOAA HPC).
- Figure 16. Frying Pan Shoals Buoy time series.
- Figure 17. Springmaid Pier Data (Myrtle Beach, SC).
- Figure 18. Radar derived rainfall estimates from Hurricane Ophelia.
Hurricane Ophelia, the fifteenth named tropical cyclone of
the record setting 2005 hurricane season, began as a weak disturbance (Fig. 1)
at the end of a decaying frontal system over the northwestern Bahamas. The
National Hurricane Center (NHC) issued the first forecast for Tropical
Depression 16 at 11 AM EDT on Tuesday, September 6, with the storm loosely centered at 26.5N, 078.6W. TD 16L slowly
drifted north-northwest under the influence of weak mid-level steering
currents. A NOAA aircraft reconnaissance found a well-defined, broad
circulation center and a 1008 millibar central pressure. Later, another NOAA
aircraft measured 27 knot flight level winds. Twenty-seven knot winds were also
measured by NOAA buoy 41010 suggesting a slow intensification of TD 16. Initial
forecasts were for TD 16L to become a tropical storm within 48-72 hours.
The National Hurricane Center upgraded TD 16L to Tropical
Storm Ophelia (Fig. 2) early on Wednesday September 7,
based on 33 knot buoy observations and
Melbourne NWS Doppler radar velocities of 36-44 knots measured between 10,000
and 12,000 feet. Ophelia continued to become better organized and strengthened
to 45 knots on September 7 as it slowly drifted northwest over warm ocean
waters. Initial model guidance was inconclusive with great model disagreement (Fig. 3).
Figure 1. Tropical Depression 16L north of the Bahamas.
TD16L later strengthened to become Hurricane Ophelia.
Figure 2. Tropical Storm Ophelia (45 knots, 1000 millibar central pressure).
Figure 3. Early model track forecasts for Tropical Storm Ophelia, September 8, 2005.
Weak steering and low shear allowed Ophelia to continue to
strengthen to 50 knot intensity as Ophelia made a slow, clockwise loop 110
miles east-southeast of Daytona Beach. Later on the afternoon of September 8,
Doppler radar detected 80-85 knot winds at 6500 feet. A dropsonde measured a
central pressure of 985 millibars and 15 knot surface winds suggesting an even
lower surface pressure. NHC upgraded Ophelia to a 65 knot hurricane (Fig. 4)
based on the radar and the in situ data. Reconnaissance flights later on
September 8 found Ophelia's central pressure had risen to 991 millibar with a
noticeable decrease in organization and a 20-30 knot southerly 250 millibar wind
through the hurricane. Despite this late weakening trend and hostile upper air
environment, NHC maintained Ophelia's
65 knot intensity until September 9.
Figure 4. Hurricane Ophelia (65 knots, 990 millibar central pressure).
Ophelia was downgraded to a 55 knot Tropical Storm early on
September 9 based upon a new aircraft reconnaissance report. Ophelia resumed a
slow 4 knot meander northwards and was forecasted to re-intensify into a
hurricane within 12 hours. Ophelia continued to show impressive convection and
outflow throughout the day. Satellite intensity estimates and objective
T-numbers kept Ophelia at hurricane strength, but later aircraft flights found
only a 983 millibar central pressure and 72 knot winds at flight level. NHC
forecast specialists upgraded Ophelia to a hurricane in the 5 PM discussion on
September 9, despite the marginal intensity measurements reported by the
reconnaissance aircraft. Weakening continued during the night of September 9
and Ophelia was back to a 60 knot Tropical Storm on the morning of September 10, slowly trudging northeastward
at 9 knots, 240 miles southeast of Charleston, South Carolina. Model guidance
continued to paint uncertainties into both the track and intensity forecast for
Ophelia (Fig. 5). Despite these uncertainties, a hurricane watch was issued for
the South Carolina coast at 11 AM, September 10th(Fig. 6).
Figure 5. Model track forecasts for Tropical Storm Ophelia on September 9, 2005.
Figure 6. NHC forecast track issued September 10, 2005.
Ophelia became a 70 knot hurricane 210 miles east-southeast
of Charleston, South Carolina during the afternoon of September 10 based upon a dropsonde measurement of 976 millibars and 78 knots at reconnaissance flight level. The hurricane slowed to 3 knots on an initial northeast track. Model forecast tracks on September 10 and the NHC official track, however, showed Ophelia making a closed loop, then making a turn to an ominous west-northwest recurving track with landfall along the South Carolina coast within 72 hours (Fig. 7). Figure 7 also showed a more cohesive model track consensus and hinted at future track shifts to the northeast when compared to previous forecast objective aids. Ophelia proceeded on a painfully slow, clockwise loop in the absence of any synoptic steering 230 miles east-southeast of Charleston, confounding forecasters and emergency managers in the Carolinas.
Imagery on September 10th and 11th(Fig. 8) hinted at a less than favorable environment for Ophelia's intensification: an asymmetric, large eye, the absence of deep cohesive convection near the eye, dry mid-level air to the west and sheared convection north and east of Ophelia.
Figure 7. Model track forecasts for Tropical Storm Ophelia on September 10, 2005.
Figure 8. Tropical Storm Ophelia (60 knots, 976 millibar central pressure).
Ophelia's slow crawl over the Gulf Stream caused upwelling
of cooler water, which acted to further constrain intensification (Fig. 9).
Figure 10 shows the weakening caused by the upwelling and eyewall corruption
due to dry air entrainment. NHC reclassified Ophelia as a 60 knot tropical
storm on September 12. Ophelia did, however, remain a large storm with tropical
storm force winds extending 140 miles from the eye (Fig. 10). NHC forecasters
began to shift Ophelia's track northwards towards the South Carolina- North
Figure 9. Hurricane Ophelias meandering track and problematic intensity changes over the Gulf Stream (Courtesy of NOAA and the University of Maryland).
Figure 10. Tropical Storm Ophelia (60 knots, 989 millibar central pressure).
Ophelia continued a slow, erratic track to the northwest towards the South Carolina coast until the
evening of September 13 when Ophelia regained minimal hurricane strength over
warmer Gulf Stream waters. Ophelia turned to a more northerly track early, and
paralleled the North Carolina coast, passing within 30 miles of Wilmington
(maximum sustained winds 42 knots gusting to 59 knots) and brushing Cape
Hatteras before turning east northeast on September 15 (Fig. 11). Ophelia was
downgraded to a tropical storm for the last time on September 16 as it passed
Cape Cod. Ophelia transitioned to an extratropical low on September 18 offshore
Nova Scotia and ultimately dissipated over the North Sea September 23.
Figure 11. Wilmington, North Carolina based National Weather Service Doppler radar image of Hurricane Ophelia.
Ophelia's track forecast was dominated by the lack of
westerly steering. Figure 12 shows Ophelia caught between the sub-tropical high
to the east and a large quasi-stationary high parked over the eastern United
States. These two features kept Ophelia confined offshore on a slow, meandering track northwards. Model resolution of Ophelia's track was inconsistent and problematic at best. The large, poorly organized eye complicated the task of accurately determining Ophelia's center of rotation. The lack of deep mean layer steering allowed Ophelia to perform two slow clockwise loops beneath the broad upper-level ridge.
The blocking highs which constrained Ophelia's meandering
track also provided weak upper-level divergence. This upper level environment
(Fig. 13) throttled Ophelia's intensity, keeping winds below 80 knots and
central pressures above 972 millibars. Ophelia finally began to track
northwards September 12 with the eastward retreat of the blocking high (Fig.
14) over the eastern United States and the approach of a cold front September
14 (Fig. 15).
Figure 12. Surface pressure 12Z, September 10, 2005.
Figure 13. 200 millibar geopotential height 12Z, September 10, 2005.
Figure 14. Surface Synoptic chart, September 12, 2005 (Courtesy NOAA HPC).
Figure 15. Surface Synoptic Chart, September 14, 2005 (Courtesy NOAA HPC).
SOUTH CAROLINA EFFECTS:
Ophelia caused high surf and severe beach erosion at Hunting Island State Park on September 8. Numerous rip currents were reported along the coast from September 8-12; fortunately, there were no injuries reported.
Ophelia's outer rainbands brushed Georgetown and Horry
counties September 12-14, causing downed trees, and minor coastal flooding on the
sound side of the barrier islands.
The North Myrtle Beach Airport Automated Surface Observing
System (ASOS) recorded 6.3 inches of rain falling September 12-14. North Myrtle
Beach Airport also recorded 20 knot maximum sustained winds and a peak wind of 38
knots along with a minimum surface pressure of 1000.7 millibars. Figure 16
shows the surface pressure and winds recorded offshore at Frying Pan Shoals
Buoy (41013) as Ophelia brushed the coast.
Figure 16. Frying Pan Shoals Buoy time series (NWS Forecast Office, Wilmington, NC).
Figure 17. Springmaid Pier Data (Myrtle Beach, SC).
Figure 18. Radar derived rainfall estimates from Hurricane Ophelia.
Ophelia's erratic track and variable intensity produced a
complex series of watches and warnings issued for the South Carolina coast:
- September 10: Hurricane Watch posted from the Savannah River to Cape Lookout North Carolina.
- September 11: Hurricane Watch dropped south of Edisto Beach.
- September 11: Tropical Storm Warning posted South Santee River to Cape Lookout.
- September 11: Tropical Storm Warning posted Edisto Beach to Cape Lookout.
- September 12: Hurricane Warning posted South Santee River to Cape Lookout.
- September 14: Hurricane Watch dropped from Edisto Beach to the South Santee River.
- September14: All tropical storm warnings dropped for the South Carolina coast.
SOUTH CAROLINA RESPONSE:
The South Carolina Emergency Management Division activated
the Emergency Operations Center on September 10 when the National Hurricane
Center began forecasting Ophelia to make landfall on the South Carolina coast.
The Emergency Operations Center remained staffed until September 14. There were
no mandatory evacuations; however, Governor Sanford issued a voluntary
evacuation for parts of Horry, Georgetown and portions of Charleston counties
on September 12. The voluntary evacuation targeted people on barrier islands,
oceanfront property, low-lying areas, and property along rivers and
streams. People living in mobile homes
and campgrounds within the targeted counties were also asked to evacuate
voluntarily. Schools in coastal counties were closed as a precaution and
several emergency shelters were opened when Ophelia threatened to make landfall
RECORDED PEAK WINDS:
Unofficial peak wind gusts through 12 AM EDT Wednesday, September 14, 2005, from various observation sites in southeastern South Carolina.
||Ben Sawyer Bridge||56|
|Caro-COOPS Capers Midshelf||51
||Arthur Ravenel BridgeDOT Sensor||49|
|Folly Beach (City Hall)||44
||Downtown Charleston (Coast Guard Station)||44|
|Isle of Palms Police Department||44
||Myrtle Beach Airport||44|
||Isle of Palms||43|
|Navy Tower R2||40
|Folly Beach C-MAN (FBIS1)||38
||Caro-COOPS Capers Island (CAP1)||38|
||Pineville (Lake Moultrie)||37|
|North Myrtle Beach||37
||Goose Creek (Goose Creek High School)||33|
||North Charleston (Rivers Middle School)||36|
|Charleston (Burke High School)||36
||Caro-COOPS Capers Nearshore||33|
|Caro-COOPS Fripp Inlet (FRP1)||30
||Caro-COOPS Fripp Nearshore (FRP2)||29|
|Hilton Head (MESONET)||29
||Beaufort County EM Office (WTOC MESONET)||26|
Special thanks to the National Oceanic and Atmospheric
Administration and its many divisions for the wealth of weather and climate
data made available to prepare this report. Specific thanks to:
- National Hurricane Center, Miami, Florida
- National Weather Service Office, Charleston, South Carolina
- National Weather Service Office, Columbia, South Carolina
- National Weather Service Office, Wilmington, North Carolina
Additional thanks to the Naval Research Laboratory
Monterey's Marine Meteorology Division for the well cataloged library of
satellite imagery used for this report.
Figures from the University of Maryland and Plymouth State
College web sites were also used for this report.