6/3/2023 0 Comments Tropical storm sally![]() ![]() The 12Z Sunday run of the SHIPS model gave an 18% chance that Sally would rapidly intensify by 30 mph in a 24-hour period, and a 12% chance it would intensify by 50 mph in 36 hours. A period of rapid intensification cannot be ruled out if the storm organizes quickly enough. How much Sally strengthens will depend in large part on how quickly it develops a vertically aligned inner core. The forecast from 0Z Sunday, September 13 (left) predicted that Sally would be a dangerous category 3 hurricane with 125 mph winds over New Orleans, but the forecast made just six hours later, at 6Z Sunday, predicted a category 1 hurricane with 75 mph winds at landfall. Predicted landfall wind speed (colors) and sea level pressure (black lines) from two consecutive runs of the HWRF model. There is plenty of heat energy in the ocean waters Sally will be traversing to support rapid intensification, as the storm should remain just northeast of a cool eddy with low oceanic heat content over the southeast Gulf. Sally will be over the very warm waters of the northeastern Gulf of Mexico, where sea surface temperatures are around 29.5☌ (85☏). But during the final six hours before landfall, those upper-level winds caused high wind shear over Laura, halting the intensification process. This band of winds will also ventilate Sally, though, providing an upper-level outflow channel capable of aiding rapid intensification.Ī similar situation had existed during Hurricane Laura when it approached landfall in southwest Louisiana in August: a strong band of upper-level winds to the north of the hurricane helped it to explosively deepen to a category 4 storm with 150 mph winds. This shear will be caused by the strong band of upper-level west-southwesterly winds over the southern U.S. (Image credit: Tropical Tidbits)īy late Monday and into Tuesday, wind shear is expected to tick up a notch, to around 20 knots, which may slow the intensification process. ![]() The thin lines (color-coded by pressure) from the individual members predicted a variety of possible landfall locations, with a stronger storm likely to move ashore farther to the east. The black line is the mean forecast from the 21 member forecasts. Track forecast for Sally from the 6Z Sunday run of the GFS ensemble forecast. The air mass surrounding Sally is reasonably moist, with a mid-level relative humidity around 65%, so dry air is unlikely to be a major hindrance to this process. The shear is expected to decrease to around 10 knots by Sunday night, which will potentially allow Sally to get vertically aligned, close off a center, and begin building an eyewall. Sally is currently tilted with height as a result of the wind shear affecting it. A weakness in the ridge of high pressure steering Sally should allow the storm to turn north on Monday, near the time of landfall. Steering currents will weaken by Sunday night, as Sally begins to feel the influence of a strong band of upper-level west-southwesterly winds over the southern U.S., causing a slowdown to Sally’s forward speed of about 5 mph by Monday. Sally is forecast to move in a general west-northwest motion toward the central Gulf Coast through Monday. (Image credit: Mark Nissenbaum/Florida State University) Forecast for Sally Radar image of Tropical Storm Sally at 11:28 a.m. Satellite and radar images showed a steady increase in the organization and intensity of Sally’s heavy thunderstorm activity on Sunday morning, though moderate wind shear of 10-20 knots caused by upper-level winds out of the northwest was keeping the northwest side of Sally’s circulation devoid of heavy thunderstorms. A strengthening tropical storm with 60 mph winds, moving west-northwest at 12 mph and a central pressure of 998 mb, Sally was bringing heavy rains to western Florida. EDT Sunday, September 13, Sally was centered 135 miles west of St. Marathon, Florida, recorded 8.13 inches of rainfall from Sally on Saturday, also setting a new September daily rainfall record. Media requests for Jeff Masters and Bob Henson.
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