Joe’s Weather Blog: Storms Yes But Questions (SUN 6/22)

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Good afternoon…getting hotter by the hour out there today as temperatures are popping with the sunshine in place. As of the noon hour we’re already well into the 80s and 90s for some are coming, especially downtown KC.

Forecast:

Rest of today: There have already been some thunderstorms across NE KS and NW MO early this afternoon. We’ll need to see if that activity can throw out an outflow boundary or two and ignite renewed activity in spots later this afternoon in all the heat out there. Chance of any one spot getting this is low at this point around the KC area. Highs near 90° (above in spots) with a heat index 95-100° (in the shade) and S winds of 10-20 MPH helping just a bit.

Tonight: Storms moving through the KC area between 7:30 and 9PM. Some locally heavy rain is possible along with some gusty winds of 30-45 MPH or so. Rainfall should be under 1″ for most areas. See radar in the discussion part of the blog.

Monday (Sunday-10PM Update): We’ve been worked over pretty good thanks to the Sunday night storms so as a result it’s tough to imagine how we get much, if any, activity on Monday aside from perhaps some scattered areas of light rain. Overall it should be an OK day after all. Highs between 80-85°.

Discussion:

I thought I’d start today with some radar talk since I’ll be showing the radar from the NWS in Pleasant Hill after this.

The good news is that some of the radars in the country have been recently upgraded to do things they were capable of doing in the past and their operation during severe weather situations has been enhanced tremendously.

I want to introduce you to two acronyms. One is SAILS and the other is AVSET. What do they stand for? SAILS stands for Supplemental Adaptive Intra-Volume Low-Level Scan. In the past the weather radar in Pleasant Hill would scan about 14 different levels through the atmosphere to get an idea on what a storm was in the process of doing. This would take roughly 4-4 1/2 minutes or so to complete. Meteorologists need that information too see if a storm is growing, weakening, creating hail and roughly what the size of the hail would be and also getting an idea of the air motions in the storm itself. The thing about it is that, especially in a tornadic situation, we’d always be most concerned about the lowest elevation scan, the one closest to the ground. What SAILS does is stop the radar from taking a FULL volume scan (roughly halfway up) and sends the radar beam back to the lowest level to “add in” another low level scan before resuming it’s previous volume scan. So in effect we’re getting a “bonus” lowest level radar picture. So instead of getting this low level scan every 4 1/2 minutes or so…now you get a lowest level scan every 2 minutes (give or take). Here is an image form the NWS in Milwaukee, WI showing what I described.

 

I think you can see why meteorologists in severe weather scenarios would want to have that extra low level scan…especially when we’re looking for radar signatures of low level rotations or straight line winds.

In addition to SAILS which at this point the NWS in Pleasant Hill has but not the NWS in Topeka…there is another upgrade called AVSET.  AVSET stands for Automated Volume Scan Evaluation and Termination

In a nutshell what this upgrade will do is give the radar operator the opportunity to tell the radar that if the radar does not hit anything important in the higher scans probing the atmosphere it can terminate the volume scan and start at the bottom and work upwards again. Here is some additional information from the NWS in Milwaukee that explains things…

Here’s what that means. When our radar is operating in severe weather mode, by default it will scan the atmosphere at 14 different elevation angles, starting at .5° elevation and peaking at 19.5°. It does this in 4 to 4 1/2 minutes (depending on the specific mode it is in). The completion of all these elevations is called a Volume Scan. There are times when the radar beam will overshoot all of the storms when it is scanning at the higher elevation angles.  At this point there is no operational benefit to continuing the volume scan at these higher elevation angles.  With the installation of AVSET, the volume scan will terminate early with the net effect of shortening the elapsed time between data collection at the more critical lower levels. 

All users of our radar data will benefit by getting more critical data at a faster interval (so long as upper elevation angles are clear of significant radar returns).  For a radar operator responsible for issuing warnings, this can help to get warnings out sooner and with more accuracy.”

Both the NWS in Pleasant Hill and Topeka now have this capability.

The radar systems were created several decades ago and replaced an aging system that was created in the 1950s. The radars were originally developed to last for about 20 years (give or take). Well here we are some 25 years later and they’re still going. They have upgrades from a hardware (dual-pol) and software standpoints…and now it appears they are going to be with us for the foreseeable future…odds are another 10-15 years. As you might imagine the expense of replacing a network of radars through the country is astronomical and with the government being what it is with respect to the weather budget outlays (especially in relation to weather data that is used on a daily/hourly basis)…we’re going to be using these things for years to come.

Perhaps of the radars could detect climate change? But I digress.

So let’s show you the latest radar perspective from the NWS in Pleasant Hill…

 

Notice the activity across N MO (as of this writing). There are some decent downpours in some of those cells. Now the question for the rest of the afternoon is whether or not some outflows will push from those storms to the south and affect the KC region in a few more hours.

There also may be a tiny little swirl in the clouds near Manhattan, KS as of 1PM…that too could create some activity in spots later this afternoon. With all this potential in the atmosphere the SPC has placed the region under a slight risk of severe weather

From tonight through Tues AM all bets are off. There should be additional storm clusters drifting our way, but how they hold together and where they track are all impossible to answer with specifics at this point…it will be a watch and wait type thing I feel and we’ll basically be nowcasting for the next 36 hours or so. The GFS has become very bullish in cranking out the rain through early TUE for the I-70 corridor (over 2″) which is possible considering how moist the atmosphere is. The NAM also has 1-2″ of rain through Tuesday in the area as well. Again still questions about how all this plays out but potential heavy rainfall is there.

To add to the complexity of things is a slow to move cold front that will be near the area later tomorrow. There are no guarantees that this will totally move through, unless there are enough thunderstorms to help push it through. So that adds additional complexities to the forecast. The bottom line is that there are various features in play that give me confidence that there will be rain out there, but unfortunately there are still questions about the whens/wheres and amounts.

Joe

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1 Comment

  • Patrick Trudel (@sedsinkc)

    Good for local NWS to have the ability to get data from critical heights near the surface more rapidly during severe weather events. This should increase lead time on tornado and severe thunderstorm warnings some more. Was helping set up for our neighborhood picnic in the park across the road from my house awhile ago and it’s quite the steambath out there today!

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