Tropical Storm Karen formed just north of the Yucatan Peninsula Friday morning (correction: that should be Thursday morning). The system had been moving northwest through the western Caribbean since early in the week. Conditions were finally favorable for development.
Now Karen takes aim on the U.S. It has been moving slowly through the southern Gulf of Mexico and toward the north-northwest. Hurricane hunters found winds of near 60 mph this morning prompting the upgrade to tropical storm status.
As of 11 p.m. EDT, Thursday, Tropical Storm Karen was 340 miles south of the mouth of the Mississippi River moving north-northwest at 10 mph. Maximum sustained winds were 65 mph in squalls to the northeast.
|The wind field around Tropical Storm Karen as of 00z October 4, 2013. Winds are measured in knots. The Yucatan Peninsula can be seen in the lower part of the image. Click on the image for a larger view. Image Credit: NOAA/NHC.|
The satellite picture for late this afternoon showed an asymmetric pattern to the storm from a southwestern wind shear. This was keeping the system from intensifying quickly as most of the thunderstorm tops were displaced east of the center. It is possible that Karen could increase to hurricane strength before landfall, however shear is expected to increase as it approaches land. This may weaken the storm before reaching the coast.
|The satellite image of TS Karen as of 11 p.m., October 3, 2013. The track models are plotted from the 00z data. Click on the image for a larger view. Image Credit: WLTX-TV.|
Mid-level shear is not much at this time, but that will change in a few days. A vigorous trough has moved into the western U.S. This is already creating an early fall storm with heavy snow expected in western South Dakota. Much colder air is spreading through the northern Rockies. The trough is digging into the West sharpening the ridge over the Southeast. Southwest winds will increase the shear and steer the storm as it make landfall.
|The 500 mb pattern for 12z October 3, 2013. Note the trough digging into the western U.S. Click on the image for a larger view. Image Credit: WLTX-TV.|
The forecast is in line with the track models. Karen should move northward to the central Gulf coast and then turn northeast. The steering currents will probably accelerate the forward motion as it makes landfall. There is a wide range of solutions as to the forward speed. This will make a big difference in the timing of the storm and the duration. It will also affect how much rain falls.
|The National Hurricane Center forecast as of the 11 p.m. EDT advisory on October 3, 2013. Click on the image for a larger view. Image Credit: WLTX-TV.|
The weather will be very warm and increasingly humid on Saturday. No rain is expected so it should not interfere with the Kentucky/USC football game Saturday evening. Clouds will be moving into the midlands of South Carolina by Sunday morning. There will be an increasing chance for showers and thunderstorms during the afternoon. Most of the rain will come Sunday night into Monday morning. The beginning and end of the rain will be determined by the storm’s speed.
Rainfall it not expected to be particularly heavy, but the computer models at the range of 4 days indicate it should be in the range of 0.5 – 1.0 inches. As usual with tropical systems there could be isolated amounts to 2 inches.
|Rainfall forecast as of 8 p.m. EDT, Monday, October 7, 2013, from the European model. Click on the image for a larger view. Image Credit: WLTX-TV.|
|Rainfall forecast as of 8 p.m. EDT, Monday, October 7, 2013, from the U.S. model. Click on the image for a larger view. Image Credit: WLTX-TV.|
Karen will likely be a tropical depression as it moves through South Carolina and it could be losing tropical characteristics. The path of the storm may increase the possibility of isolated tornadoes, but that will be closer to the coast if the center moves through the Midlands. Winds gusts to 25 or 30 mph may be possible, but the winds should be less than 20 mph most of the time.
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