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Tanith

Weather terminology

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Starting this topic because well, I'm curious. And I thought it would help us all to learn more.

Often I see or hear phrases used by meteorologists that aren't entirely clear to me. For example, "brief spin-up tornado" is getting a lot of use these days, as one would expect during springtime. But what does it mean? I am guessing it simply means a weak, brief tornado but wanted to be sure.

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Good topic!!!

Often, there will be specific severe weather parameters that cause these quick spin up tornadoes, specifically a low CAPE/high shear environment.  Shear is the rotation or twist in wind direction as you go up in altitude, and CAPE (Convective Available Potential Energy) is what is sounds like, the amount of energy available to a given thunderstorm. 

If both are available in sufficient quantities, you can get big thunderstorms that can produce large tornadoes. But if you're missing some of those ingredients, such as the CAPE, then the energy needed to sustain a big storm and strong tornadoes isn't there. But... with strong shear, you can still quickly spin up a weak tornado and have it disappear within a couple of minutes. 

The reason that quick spin-up tornadoes are very difficult to forecast and issue warnings for are due to a weakness with low level radar scans. The NWS radar updates every 2 to 5 minutes when the radar enters severe weather mode or SAILS - Supplemental Adaptive Intra-Volume Low-Level Scan. During this time span, a quick spin up tornado can form and immediately disappear before the radar can "see" the tornado signature. These quick forming tornadoes are dangerous since they can strike with little warning, but due to the nature of the quick spin up and spin down, they are generally very weak and in the EF-0 to EF-1 range. 

2 hours ago, Tanith said:

Starting this topic because well, I'm curious. And I thought it would help us all to learn more.

Often I see or hear phrases used by meteorologists that aren't entirely clear to me. For example, "brief spin-up tornado" is getting a lot of use these days, as one would expect during springtime. But what does it mean? I am guessing it simply means a weak, brief tornado but wanted to be sure.

 

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So, one thing I have been reading more lately in relation to sever weather chances are the phrases “Bowing” and “Squall Line” what do these mean?

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16 minutes ago, Asperman1 said:

So, one thing I have been reading more lately in relation to sever weather chances are the phrases “Bowing” and “Squall Line” what do these mean?

A squall line is:

Quote

A squall line or quasi-linear convective system is a line of thunderstorms forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts.

 

Bowing in a squall line is usually an indication that there are high winds causing the line to "bow" Last night the MCS that was pushing in from Alabama had a bow to it. Those lines that do have a strong bow to them generally have higher straight-line winds and wind damage.

2880px-Bow_echo_diagram.thumb.png.217338c1fadf1e10fe69fc256fd87d29.png

Quote

Typical evolution of (a) into a bow echo (b, c) and into a comma echo (d). Dashed line indicates axis of greatest potential for downbursts. Arrows indicate wind flow relative to the storm. Area C is most prone to supporting tornado development.

 

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Snap346062641-19.thumb.jpg.fef0a7a7c66ea97ae8a9d6d508138282.jpg

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
711 AM EDT FRI APR 19 2019

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  ROCKDALE COUNTY IN NORTH CENTRAL GEORGIA...
  SOUTHWESTERN BARROW COUNTY IN NORTH CENTRAL GEORGIA...
  SOUTHEASTERN DEKALB COUNTY IN NORTH CENTRAL GEORGIA...
  GWINNETT COUNTY IN NORTH CENTRAL GEORGIA...
  NORTHWESTERN WALTON COUNTY IN NORTH CENTRAL GEORGIA...
  NORTHWESTERN NEWTON COUNTY IN NORTH CENTRAL GEORGIA...

* UNTIL 115 PM EDT FRIDAY.

* AT 711 AM EDT, DOPPLER RADAR INDICATED THUNDERSTORMS PRODUCING
  HEAVY RAIN ACROSS THE WARNED AREA. UP TO THREE INCHES OF RAIN HAVE
  ALREADY FALLEN. FLASH FLOODING IS EXPECTED TO BEGIN SHORTLY.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
  LAWRENCEVILLE, CONYERS, WINDER, SNELLVILLE, BUFORD, LILBURN,
  LOGANVILLE, AUBURN, STONE MOUNTAIN, DACULA, GRAYSON, OXFORD,
  LITHONIA, WALNUT GROVE, BETHLEHEM, BETWEEN, CARL, LAKEVIEW ESTATES,
  GEORGIA INTERNATIONAL HORSE PARK AND CANDLER-MCAFEE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TURN AROUND, DON'T DROWN WHEN ENCOUNTERING FLOODED ROADS. MOST FLOOD
DEATHS OCCUR IN VEHICLES.

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