Derecho Storm Have some funny help getting started? May 3 2009 Weather Wars

Derecho Storm Have some funny help getting started? May 3 2009 Weather Wars
Rare derecho sweeps across Southern US - widespread damage

Johnny Kelly
Jackson Examiner

Wed, 06 May 2009 03:28 UTC
On Sunday, a significant windstorm called a derecho, swept across 5 states, knocking down trees and power lines across the South.

Southeast Texas, Central Louisiana, South Mississippi, South and parts of Central Alabama, and North Central Georgia all were affected.

© Jacksonville Examiner
A derecho is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line, usually taking the form of a bow echo.

The bow (radar) echo formed during the early morning hours around 6 am in Southeast Texas. These storms began to quickly bow out, signaling strong winds.
The derecho intensified rapidly as it progressed into Central Louisiana.

© WSI


The National Weather Service in Shreveport has confirmed, widespread damage in some parts of Central Louisiana was created by winds near 110 mph. In addition to the damaging winds, 4 tornadoes were confirmed along the path of the derecho. Several people were injured.

The derecho remained intense as it crossed South Mississippi, forming a sharp bow echo. Several areas of intense wind damage was confirmed by the Jackson National Weather Service. Winds as high as 100 mph were confirmed. In addition to the damaging winds, 5 tornadoes were also confirmed.

© WSI
Two of the tornadoes were long tracked. One tornado remained on the ground for 10 miles, tracking from Simpson into Jefferson Davis County. The other tornado remained on the ground for 18 miles, tracking from Northern Covington into Southwest Smith County. One woman was killed as a result of a falling tree during the high wind event across South Mississippi.

As the derecho continued into South and Central Alabama, it began to weaken but tornadoes became more of a threat than the damaging winds as 5 tornadoes were confirmed by the Birmingham National Weather Service.

One tornado remained on the ground for 16.58 miles as it tracked across St. Clair County. Two other tornadoes were confirmed in North Alabama, with a total of 7 tornadoes confirmed across the state.

© WSI
(Note: Over 30 tornadoes have been confirmed in Alabama since April 10)

Overall, wind damage was reported from the Mississippi state line, east across South and parts of Central Alabama to the Georgia state line, as winds of 60-70 mph moved across this area.

The long lived derecho continued to weaken as it entered into Georgia. Winds over 50 mph were confirmed in many areas. Numerous trees and powerlines were downed into the Atlanta area. Over 130 wind reports and over 20 reports of tornadoes occurred along the derecho's path.

This was a significant long lived derecho event that lasted over 13 hours!

Category:

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[Bororeed]

The beam that you see coming from the radar is the sun setting. This happens at every radar site when it rises and when it sets. The large area of blue that appears to develop is the near surface inversion of dust, pollutants, etc, that the beam is striking as it gets trapped by this inversion. This is common is summer months due to the high humidity levels and pollution levels. The beam follows the sun as it sets on the horizon, which is why it appears to move as well.

[DrHolyhellcat]

@Bororeed please show me one other radar with this on it that did not result in a storm. Please.

[DrCumulus]

@DrHolyhellcat No problem :)

[DrHolyhellcat]

@Bororeed It's just these storms were unexpected, and very strong. In other countries, the weather modification is not blacked out by the media. I do believe now, even our own .gov is starting to discuss it. I have not seen this on any other radar. I will agree with you, there was something there.

[DrHolyhellcat]

@Bororeed and only occurs at sunup or sunset? The Dallas storm you see, the sun was set.

[DrHolyhellcat]

@DrCumulus  Thank you!

[DrHolyhellcat]

@poopsyproductions  yes, and they were some really strong storms

[DrCumulus]

@DrHolyhellcat did you know on the radar when you go to save image it will save the furthest right checked box in the legends, if you need more info, i can help, i just did a weather course on the radar for NOAA :)

[poopsyproductions]

That blue stuff is ground clutter right? I'm pretty sure that is what you're seeing.

[Bororeed]

Here's you explination:

Sun Interference. Twice a day, at sunrise and sunset, the radar experiences interference from the electromagnetic energy emitted by the sun. There is a point at sunrise and sunset where the radar dish points directly at the sun and is hit with this energy. This is then displayed as a spike of returned energy on our display. It is brief, typically only occurring during one volume scan

[Bororeed]

What's the simple math then? Many, and I mean many studies show that a significant number of cercho event start near sunset. Tjis is when the warm air cap aloft is beginning to lose some of it's grip and clouds are more likely to bust through the inversion. Also, last time I looked at this video, there are no radar echoes visible, other than the lighter colors, which clearly indicate a lower level inversion near the surface.