Saturday, March 10, 2012

Severe Weather Threat for Tomorrow

I am printing a general risk of thunderstorms with embedded stronger cells for southern Missouri and most of Arkansas as a small jet streak and lower level jet stream combine to produce some wind shear that will be of use to any storms that try to develop. While instability mechanisms will not be the most abundant, a higher theta-e (basically increases instability in higher theta-e) and negative tilt to the storm system should cover the cost.

There is an orange area in central Arkansas, which indicates my thinking of a potential of some potential weak super cells and severe weather reports tomorrow. I outlined an orange area as the most recent WRF highlights some high-precip storm cells in that area, usually indicative of some severe weather in those cells. Also, the highest theta-e may be present in the general area in orange, adding instability to the storm cells. Additionally, the Storm Prediction Center has highlighted central Arkansas for a 30% risk of severe weather, which is a high-end slight risk of severe weather. The lower level jet stream will also be over 40 knots, increasing wind shearing and also the risk for some tornadic activity in the atmosphere.
Meteorologists use something called a hodograph to determine if the atmosphere is conductive for tornadoes. It is looking like the atmosphere will be supportive for some spinning motion, but again, instability is crucial, and we will have to see if the higher theta-e and negative tilt to the storm will step up to replace that missing CAPE.


Severe Weather Risk in Arkansas for Tomorrow

The Storm Prediction Center has issued a slight risk for severe weather tomorrow in Arkansas, with even a 30% risk of severe weather present in the state, making for a high-end slight risk area.

This risk had not gone unnoticed and has been tracked here at The Weather Centre for at least a couple days.

The storm system responsible will be ejecting northeast. As it does, showers and thunderstorms will loosely form along a somewhat linear boundary, maintaining the possibility for some discrete super cells. Here's a very localized image forecast off the most recent WRF, thanks to WxCaster.

This is 6-hour precipitation, so it does not show the actual storm cells. However, it is showing several strong storm cells, judging by precipitation put down in this image. Arkansas looks to be raked by these storms tomorrow.

Here's what's holding me back from being convinced that something big will happen. There will be a lot of helicity in the atmosphere, but the problem is the lack of instability, which is in color. To get the strong storm cells, we would want CAPE values in the yellow, and I believe that is why the SPC will not go with a moderate risk of severe weather tomorrow.

Here's one of the more intense WRF members from the University of Illinois WRF member suite. It shows strong storms raking Missouri and Arkansas.

This is maximum reflectivity, meaning this is theoretically as bad as things could get with the storms, and  believe that this will not verify in Missouri. Arkansas seems more reasonable, however, with those red lines likely being more of discrete super cells than diagonal line segments.

Tomorrow, we will be your storm central for the severe storms, here at The Weather Centre.

Severe Weather Possible in Long Range

A storm system looks to come riding in on a 120 knot jet stream that could make for some severe weather in the long run.

This is the long range, so things will definitely change, but when you get a storm system as strong as this producing this much pressure on a jet stream, something exciting is bound to happen.

As much as 80 knots of deep layer shear is also eyeing the Plains, making that region the potential hotspot if this system is to verify. It has been showing up on several runs recently.

Seeing as the jet stream will be displaced from Canada to Arizona, some cool air is expected to be surrounding this storm system. This would only increase the threat of severe weather as cool Canadian air crashes against the warm Gulf air freely flowing across the eastern half of the US, depicted by the jet stream displaced far north.


South Plains in Line of Fire for Strong Thunderstorms on Sunday

Here is member 'G' of the WRF member suite at the University of Illinois, depicting some very strong thunderstorms possible in the Southern Plains Sunday afternoon.

A strong storm system will be ejecting northeast across the middle and upper plains, bringing with it a frontal boundary that will be producing showers and thunderstorms. Lack of instability mechanisms means this will not be a major severe weather event.

Because a strong storm system will be moving northeast rather than straight east, a jet streak is likely to form in response to pressure on the jet stream.
The jet stream is like a rubber band- flexible but still has some limits on how far it can stretch. A storm system is like a finger pulling on the rubber band. In response to more pressure from pulling on the rubber band, there will be increased pressure from the rubber band to move the storm system back and thus ease the rubber band. This increased pressure in the atmosphere results in higher jet stream winds.
These higher jet stream winds of over 100 knots may very well fuel some more intense thunderstorms closer to the back end of the storm cluster.

These storms will probably be putting down some gusty winds and occasional small hail. However, as previously mentioned, a lack of instability will keep the storms from getting too strong.