Tropical Storm Grace has shown an increase in thunderstorm activity overnight but there is very little organization being indicated on the satellite loops. Tropical Storm Grace continues westward and into an environment of strong wind shear which should weaken it to a depression later today and to a remnant low perhaps in another day or so.
SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...14.1N 41.0W ABOUT 1360 MI...2185 KM E OF THE LESSER ANTILLES MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 20 MPH...31 KM/H MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. The National Hurricane Center is forecasting Tropical Storm Grace to move along and weaken into a depression and then to a remnant low over the next few days .
The satellite loop shows the shear already blowing tops of the thunderstorms away to the northeast and the shear only increases as Tropical Storm Grace heads further to the west. It is hard to see how Tropical Storm Grace will survive this over the next 96 hours because the shear is only going to increase even more with time.
The first map above shows the average shear over the next 5 days while the map below shows the shearing forecast specifically Thursday night 8pm. The shearing if anything actually increases through much of the Atlantic south of 25 degrees north. Also shearing is forecast to increase off the African coast which may effectively end the Cape Verde Season a few weeks earlier than usual. The very strong El Nino pattern is just to overpowering for tropical systems to overcome this season.
Wind shear is simply an atmospheric condition where wind speed increases as you go higher in the atmosphere. Tropical Storms abhor strong wind shear environments as they prevent the storm from achieving a straight up and down uniform vertical structure. The increasing winds aloft blow off the tops of thunderstorms away from the circulation center. In time the low level center becomes completely exposed and separates from the thunderstorms, weakening into a low level swirl of low clouds. This happens a lot in the Pacific once storms move northward into high shear environments. Nothing in the long range pattern suggests that this overall pattern is going to change anytime soon so tropical storm development will be limited to small areas were shear is minimal. There are very few areas right now that qualify with this condition.
The picture above is the visible satellite of Tropical Storm Grace The low level center appears to be right on the edge of the convection and the tropical storm has taken a oval shape is upper winds distort the circulation. The picture below is of an area of disturbed weather southeast of Bermuda that is sitting in a low shear environment and could develop into a tropical cyclone over time. The system is forecast to remain stationary over the next few days.