Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 8:29 PM GMT on September 29, 2010
The season's fourteenth named storm, Tropical Storm Nicole, is here, but not for long. Observations from the Hurricane Hunters and satellite imagery show that the storm is being stretched along a north-south axis as it gets absorbed into a trough of low pressure along the U.S. East Coast. A separate extratropical storm is developing along a stalled-out front along the coast of South and North Carolina, and much of Nicole's moisture and energy will begin feeding into this new storm today and Thursday, leading to the demise of Nicole by Thursday. Nicole continues to dump torrential rains on Jamaica, Cuba, the Cayman Islands, South Florida, and the western Bahamas as it tracks steadily north-northeastwards up the U.S. East Coast. Some rain amounts from Nicole since yesterday morning include 9.14" at Plantation Key, FL and 8.47" at Irwindale in western Jamaica. In Southeast Florida, radar-estimated rainfall amounts of 4 - 10" are common across the coast (Figure 1.)
Surface observations don't show any winds in excess of 25 mph near the center of Nicole, and the strongest winds are located several hundred miles southeast of the center. Some of the stronger winds measured today were at Guantanamo Bay, Cuba (39 mph, gusting to 53 mph) and Cayman Brac Island in the Grand Caymans (33 mph, gusting to 43 mph).
Figure 1. Radar-estimated precipitation for South Florida. Nicole has brought over ten inches of rain to the Middle and Upper Keys.
Extreme rainfall for eastern North Carolina
In North Carolina, the the precursor moisture from Nicole has generated an epic rainfall event. Wilmington, NC has measured 15.83 inches of rain over the past three days, as of 4pm EDT. This is the city's second highest 3-day total in history, behind the 19.06" that fell in September 1999 during Hurricane Floyd. The non-tropical low pressure system developing along the South Carolina/North Carolina coast today will move northwards, giving North and South Carolina an additional blast of heavy rain tonight, which will be followed by more heavy rain from Nicole (or Nicole's remains) Thursday morning. By the time the rains from Nicole finally clear the area Thursday afternoon, an extra 5 - 10 inches will have fallen, and Wilmington will be looking at a 4-day rainfall total of 20 - 25 inches, the highest in recorded history there. Severe and damaging flooding is likely today and tomorrow from the record rains. Fortunately, eastern North Carolina was under moderate drought conditions prior to this week's rainfall onslaught, so the flooding damage will not be as great as the billions of dollars of damage wrought by Hurricane Floyd.
Figure 2. Radar-estimated precipitation for North Carolina since Saturday shows that the precursor moisture from Nicole has brought widespread rain amounts in excess of eight inches to eastern North Carolina, with over fifteen inches (white colors surrounded by dark purple) near Wilmington.
Elsewhere in the tropics
A tropical wave a few hundred miles east of the Lesser Antilles Islands is generating a modest amount of disorganized heavy thunderstorms. The wave is under a moderate 10 - 20 knots of wind shear, and has some dry air to the northwest of it that is interfering with development. None of the models develop this disturbance, and NHC is giving it a 10% chance of developing into a tropical depression by Friday. The wave is headed into a region of higher wind shear, and is not likely to develop.
Another tropical wave located about 900 miles west-southwest of the Cape Verdes Islands is more of a threat. This wave is currently moving west at 15 - 20 mph, and is generating a large area of disorganized heavy thunderstorms. Wind shear is 10 - 20 knots over the wave, and shear is forecast to decline by late this week. The latest 2am EDT runs of the NOGAPS and GFS models show some slow development of the wave late this week, and the storm is forecast to pass near the northern Lesser Antilles Islands on Sunday or Monday. NHC is giving the wave a 10% chance of developing into a tropical depression by Friday.
Disturbed weather will continue in the Western Caribbean for at least the next ten days, and the NOGAPS and GFS models continue to predict that the region could spawn a tropical depression 6 - 7 days from now. However, the models are being less aggressive about such a development than in yesterday's runs, and the models have not been consistent about the timing or location of such a storm.
I'll have an update Thursday morning.
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