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Looking Into Developing Late Week Rain Chances & Cooler Weather

Good morning bloggers,

The weather pattern continues to cycle regularly and this next part of the pattern is right on schedule.  Plotting the 500 mb chart is usually done by drawing in the 540 line and the 570 line.  Do you know what I mean by the 540 and 570 lines?  This chart below shows the flow at 500 mb.  The top of the atmosphere has no weight at all above it, with no atmosphere left. The pressure at the top of our atmosphere is zero, or 0 mb.  MB stands for millibar.  500 mb is the middle of the atmosphere in weight as the pressure near the surface has an average of 1013.25 mb, or 29.92 inches of mercury pressure.  So, it is near 1000 mb, and 500 mb would be about half way up, or around 18,000 feet. This is the best level to find the LRC. The LRC affects every level, however.  The 570 and 540 lines are the 5,700 meter level and 5,400 meter level. What? This map shows the level where the pressure is 500 mb. So, the pressure is exactly the same, but at different levels, and this allows us to find the storm systems, the cyclones, and the anticyclones.  I drew in the 5,700 line, or the 570 line, and I drew in the 540 line, which is just that one circle way up north showing the vortex over Canada.  The main jet stream is farther north now that it has been all year. The weakest and farthest north jet steam usually happens during the last week of July into the first week of August, so it is happening in this next two week stretch. Then, the jet stream begins strengthening.  And, I am sure we are ready for the new pattern to begin evolving. The new LRC does not truly begin, however, until early October.

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On this map, the H shows where the center of each anticyclone is located.  The southwestern United States will be sizzling hot this week.   Kansas City will be firmly under the control of northwest flow aloft around that vortex in Canada. This will provide the conditions favorable for a pretty nice flow of cooler air from Canada making it into the plains.  And, it will provide the set up for a very good chance of thunderstorms later this week into next weekend.

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The surface map above shows the front stalling over Kansas.  In May the fronts stalled just north of this position leaving us hot and dry. In the late July version, thank goodness, the front is farther south and we have a pretty good chance of seeing thunderstorms and experiencing the cooler air.  Let’s see how this all sets up later this week.

Thank you for spending a few minutes of your day reading the Action Weather Blog featuring Weather2020 and the LRC. Go over to the Weather2020 blog to join in the conversation.

Gary

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