The map above (from CIMSS) shows the shear tendency and total tropospheric wind shear. We can actually see both the polar jet and the subtropical jet. The environment is just too hostile right now to support tropical cyclone activity.
It would be an understatement saying there is a lot of rainfall coming next week, but when (and why)? As this lovely map above shows, the bulk of the rainfall will be confined to the Gulf Coast and areas to the west of the Carolinas. Here is a map of the upper level low that will eventually act as kerosene on a burning fire for storm activity.
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| The upper level low is over Texas on Sunday (300mb level winds, from www.weather.unisys.com) |
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| And the 500mb vorticity for Sunday, from www.weather.unisys.com |
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Saturday still has a very strong dry layer aloft, which all but crushes rainfall chances across the Carolinas. Note the pre-existing upper level high across south Florida and the moisture plume aloft it is carrying towards the Gulf States.
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| Saturday's 500mb moisture content |
The charts on unisys do not make it clear but the upper level low over Texas eventually drops down towards the Gulf Coast as a trough in the northerly branch of the jet stream deepens. This trough deepens as it traverses down the Rockies. This stretches out the upper level low component to it, contracting the trough and making a more favorable environment downstream. The upper Midwest will have a stormy day on Sunday. The deepening trough will shunt the southern branch farther south as well. Thus, even Sunday is precipitation free for the Piedmont but we will see the cloud cover roll in. There is a chance of a popup shower in the Mountains on Sunday.
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| Sunday's 300mb winds |
While the precipitation is confined to the southern states on Sunday, a now synoptically supported upper level flow in conjunction with a surface moisture flow off the Gulf will REALLY enhance thunderstorm activity across the Gulf Coast. Now, we have a very long line of thunderstorm and rain activity extending along the Mississippi River.
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| Sunday's upper level relative humidity. |
With the deepening trough for the northern branch of the jet stream, the moisture plume from the upper level low over the Gulf Coast (and from the southern jet) are both carried much farther into the United States.
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| Sunday's 500mb vorticity |
The subtropical jet will provide additional moisture on Monday. Hence, this is the kerosene on the fire and when we will start to see our rainfall and thunderstorms. I think the model output has the rainfall as too high, but I can see between a half inch and 3/4" for Monday alone.
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| Monday 300mb winds |
The precipitation doesn't make it into the Piedmont until Monday morning. I think the models are pinging too high a rainfall amount but I do support the end result of there 1-2" up to Wednesday.
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| Monday upper level relative humidity |
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| Tuesday upper level humidity |
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