A potential for strong to damaging winds exists Friday morning across eastern NC, especially in northeast NC and southeast VA. A 1007 mb surface low upstream near Savannah GA at 01Z is progged to begin a period of rapid intensification as it tracks northeast along the Carolina coast early Friday morning. Virtually all model guidance is indicating synoptic pressure falls on the order of 7-11 mb/3-hr in that area, with a 50-60 knot LLJ as low down as 950 mb, in the presence of heavy precipitation in vicinity of the track of the H85 low.
Although diurnal timing and the CAD wedge currently in place would argue for little high wind potential on the western periphery of the surface low, especially in the WFO RAH coastal plain, strong pressure falls will give rise to strengthening and increasingly isallobaric (northerly) surface winds, which will result in low-level cold advection and steepening low-level lapse rates (sfc-1000 ft agl) and may help to erode the near-surface stable layer, allowing for better downward momentum transfer (than would otherwise be the case) in the presence of heavy precipitation.
The best chance for strong winds will be along the immediate coast (esp. OBX) in southerly flow on the eastern periphery of the surface low where at least the 18Z NAM simulated reflectivity product shows isolated convection penetrating inland along the coast. Interestingly, the aforementioned simulated reflectivity product shows isolated low-topped convection ‘pinwheeling’ N/NW further inland, most likely in association with strong low-level steering flow in vicinity of the H85 low.
It is difficult to pin down exactly where (or even if) there will be an enhanced potential for strong winds inland along or just west of the track of the H85 low given that it will highly depend on the exact track of the surface low, the deepening rate over the Carolinas, and the location of the strongest pressure falls – especially since forecast models are notorious in having a difficult time nailing down the track of a surface low within 25-50 miles when a cold air damming wedge is present.
Additionally, although the upper level pattern is not as amplified as it has been in most of the gravity wave cases I’ve seen, it is certainly possible that gravity waves could be present given the presence of a ducting layer associated with CAD and ageostrophic adjustment aloft in association with the presence of an amplifying shortwave over the Carolinas.
NWS Raleigh, NC
Peak Wind Gusts During the Morning of 02/08/2013