Fred, Is that You?
Posted September 21, 2009
It may have been declared a remnant low way back on the afternoon of Saturday, Sept 12th, when its center of circulation was 3,012 miles from Raleigh (as estimated on the iControl Stormtracker in our "Hurricanes" section), but what was left of former major hurricane Fred has continued to drift west across the Atlantic in a weak state ever since, variously in the form of a remnant low or tropical wave.
By midday Sunday, it had made its way to a position a few hundred miles east of Florida and was interacting a bit with a stalling frontal boundary to its north, with little closed circulation noted, but some clusters of convection scattered about (first attached satellite image, from the links at the National Hurricane Center web page) while by today at around 8:15 am it had drifted a little farther northwest, with a notable cluster of showers and storms on its east side (near 30 North 70 West in the second image).
You can see how yesterday's Global Forecast System computer model was treating the trough in the next three images, in which the system shows up as a series of northward pointing "kinks" in the isobars off the southeastern coast highlighted by an orange color contour that corresponds to an area with some cyclonic rotational energy. In each successive image (from Penn State's tropical models page), it progresses toward and then into the southeastern U.S., and thus it appears that in a long-delayed, roundabout and much weakened manner, Fred will end up bringing some precipitation to parts of our area.
There are still the usual uncertainties about timing and intensity as I write this early on Monday, but for now it looks as though we will see the chance of rain increase from the east through the day on Tuesday, and by Tuesday evening there is a reasonably good chance many of us will see some sprinkles or showers, with a slight chance at some thunder. The frequency and intensity of rain will likely be greater over the eastern half or so of the viewing area, and potentially drop off rapidly farther west. Recent model results suggest anywhere from around 1 to 3 tenths of an inch of rain by later Tuesday evening in the Triangle and perhaps one-half to three-quarters of an inch over the eastern coastal plain, but of course localized bands and streaks often end up producing notably more or less rain than the general average. All told, Tuesday should be a good day for keeping an umbrella or poncho in the vicinity for those of us in the eastern half of North Carolina, while those in the mountain and foothills to our west who have been very wet for the past 2-3 days should see rain coverage diminish a good bit.