WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Ophelia lumbering towards the coast
Ophelia is lumbering towards the coast at a snail's pace of 4mph, and remains over warm enough water (82-83F) to keep a slow strengthening trend going. Long range radar out of Wilmington, NC shows an modest increase in intensity and coverage of the rainfall, but the inner eyewall of about 20 miles diameter that was trying to form this morning has collapsed. Now that Ophelia is moving, the upwelling of cold water stirred up by her winds is not going to be an inhibiting factor. However, the water temperatures within about 80 miles of the coast cool off to about 78 - 80F, and this should put a halt to Ophelia's slow intensification once she gets close to the coast on Wednesday night or Thursday morning.
Although NHC has been advertising Ophelia as having peak winds of 70 mph, the actual peak winds measured at the surface by buoys is 50 mph. Apparently the stronger winds at higher altitudes measured by the Hurricane Hunters and by Doppler radar are not mixing down to the surface as efficiently as usual for a hurricane. The NOAA aircraft's SFMR instrument has measured surface winds of 55 kt (63 mph), but this estimate is not supported by buoy measurements, and the SFMR winds are probably too high by 5 knots.
Shear is low (5 knots) and the upper-level outflow good, but there is still too much dry air and cool water surrounding Ophelia to support anything stronger than a 80 mph Category 1 hurricane. The chances of a coastal observation site actually recording sustained winds of hurricane force (74 mph) are probably about 20%. Wind damage from Ophelia should be low, but her winds have had a lot of time to pile up a big mound of water near her center, and the storm surge of 4 - 6 feet will cause most of this storm's damage.
Flooding of low-lying areas from rain could be a problem in some places; areas just south of Wilmington, NC have already received 4 - 5 inches or rain. Another 5 - 10 inches of rain is likely from this wet, slow-moving storm. If eastern North Carolina were not under mild drought conditions, this would have been a much more serious storm.
Figure 1. Surface wind estimates this afternoon from the NOAA aircraft's SFMR instrument show a large area of tropical storm force winds, primarily on the west side.
Jeff Masters
Although NHC has been advertising Ophelia as having peak winds of 70 mph, the actual peak winds measured at the surface by buoys is 50 mph. Apparently the stronger winds at higher altitudes measured by the Hurricane Hunters and by Doppler radar are not mixing down to the surface as efficiently as usual for a hurricane. The NOAA aircraft's SFMR instrument has measured surface winds of 55 kt (63 mph), but this estimate is not supported by buoy measurements, and the SFMR winds are probably too high by 5 knots.
Shear is low (5 knots) and the upper-level outflow good, but there is still too much dry air and cool water surrounding Ophelia to support anything stronger than a 80 mph Category 1 hurricane. The chances of a coastal observation site actually recording sustained winds of hurricane force (74 mph) are probably about 20%. Wind damage from Ophelia should be low, but her winds have had a lot of time to pile up a big mound of water near her center, and the storm surge of 4 - 6 feet will cause most of this storm's damage.
Flooding of low-lying areas from rain could be a problem in some places; areas just south of Wilmington, NC have already received 4 - 5 inches or rain. Another 5 - 10 inches of rain is likely from this wet, slow-moving storm. If eastern North Carolina were not under mild drought conditions, this would have been a much more serious storm.
Figure 1. Surface wind estimates this afternoon from the NOAA aircraft's SFMR instrument show a large area of tropical storm force winds, primarily on the west side.
Jeff Masters
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.