Weather Radarmeteorological radar
Weather freaks posted radar pictures in all major newspapers during the last heavy storm. As not everyone is a weather freak, one of the most frequently asked question was "what do I see? "Don't worry - this is how you see a weather radar twister.
In the United States, double radar is probably the biggest advancement in weather engineering in the last 50 years. Prior to the early 1980', the weather radar could only recognize rain. From 1988, the National Weather Service introduced a new radar model, sometimes known by the name WSR-88D, which stood for Weather Surveillance Radar-1988, DP.
" The Doppler radar can not only see the rainfall itself, but also see in which direction the rainfall is travelling and how quickly it is travelling - in essence, it can recognise both rainfall and prevailing weather conditions. This winch-facing device is known as the "basic speed" because it measures the speed of the rains and hails in storms.
Being able to see the wind in a storm is a biggie. Weather forecasters almost only issued warning tornadoes if someone discovered one on the surface and announced it, or if the storms on the radar had the classical "hook", which possibly indicated a powerful one.
As they acquired the capability to see the wind rotate in a storm, the time to prepare for the twister alert significantly accelerated, which has saved innumerable human life in recent years. The most tornados are relatively feeble and short-lived, and you would never know they are there when you look at a radar picture with rainfall on a continuous basis.
Here is an example of a rather small super cell with a classical catch when she pulled a big Keil twister through the city of Midtown Mobile, Alabama on Christmas Day 2012. A look at the radar reveals little uncertainty that the wind is turning and is likely to trigger a twister. At the other end, take this picture of Mississippi South-Central back on April 7 this year.
When this picture was taken, there was an equally powerful but three fold bigger twister (1/3 of a nile wide) ripping through a few small farming towns. It is fully covered in rains, so that it looks no different on the rainfall picture than its neighbour. Had this happened in 1982 instead of 2014, weather forecasters would never have given a twister alert if someone hadn't phoned to call.
Here is the same opinion, but with the basic speed picture, which tells us what the wind does in the storms. If you don't know exactly what you see, it's clear that something unusual is going on in the middle of the picture. There was the twister, and this basic speed picture screams only "rotation", when there was no clip on the reflection picture (precipitation).
The basic speed shows wind that either moves in the direction of the radar location or away from it. Most points of sale that publish/display radar images show wind in the form of scarlet colours that move away from the radar, while verdant colours show wind in the direction of the radar. The darker shades indicate lower wind speeds, while the lighter colours indicate them.
Usually the basic speed model is expressed in nodes, but in my radar application I have added enough coding to turn the pictures into MPH, so this is the standard used in the pictures in this article. Finding out where the radar location is most of the elapsed can be difficult, but you don't have to be too worried.
If you look at the radar to see a twister, you want to look for pairs. One pair is when a storm of colours of red versus a storm appears next to each other on the basic speed screen. If pairs are large and relatively feeble, this is a sign of a wide spin within a storm that must be observed but does not show a twister on the floor.
If the pair is narrow and light, it shows a sharp spin within a storm that could create (or are producing) a torch. Here is an example of the pair made by the Mississippi based Mississippi based on the example above. One can see that the colours are very similar and relatively light, which shows a sharp spin within the storm.
Radar rotations vary greatly from gale to gale. At times a twister is so small or happens so fast that the radar has no chance to spot it. In particular, this applies to tornados that appear in far-away tropic landfall regimes, windstorms and windstorms.
This is a side-by-side elevation of the rainfall (left) and wind (right) of a 600-yard EF-3 twister as he relocated through Lincoln County, Tennessee during the twister eruption last weeks. There is the classical Hookenecho in the rainfall pattern to the right, and the winches on the basic speed pattern to the right show a very well delineated flow with strong winches that wrap up in the twister.
Although the picture is stable, the couple is so intensive that you can almost see it rotating. Weather radar technology's latest advancement is the relatively new system of " Dual -Polarisation ", which the NWS has just installed throughout the state. As well as allowing us to see where and how quickly the rainfall moves, double-pole radar enables us to see the magnitude and form of the object from which the radar ray bounces back to the radar location.
Correspondence coefficient", CC for short, is one of the two pole devices that help the meteorologist to recognize a twister. Near 100% means that everything in this area is consistent - all rainfall is the same and of the same form, which means that there is probably only a rainfall.
When you have a small area with very low CCs within the heavy rotational range shown in the basic speed pictures above, there is a good possibility that you will see the radar ray reflected by rubble whirling around within a tail. Two pole has been used to verify the Mississippi twister that I used as an example in this article.
Throughout the twister eruptions last weeks it was also used in detail to help weather forecasters realize if the thick turn produced twisters. Above the tweet shows the CC picture for the EF-4 twister that hit Tupelo, Mississippi last weekend. In the middle of the picture, the low CC-value shows the rubble in the atmosphere.
Well, since you know (hopefully) what to look for on the weather radar when there are some sort of tornados somewhere in the land, don't look for a twister on the radar when you go under a twister caution. Weather forecasters warn against tornados for good reasons - whoever is under one is in jeopardy.
The information is primarily intended to help you comprehend what you see when the weather is far enough away from your site that you are not in jeopardy. Watch The Vane on Facebook (and the writer on Twitter) for more weather.