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Month Long Forecast For May

Good morning bloggers,

Kansas City Weather Time-Line:

  • Today: Mostly sunny with increasing afternoon clouds. High: 67°
  • Tonight: A chance of rain near I-70 in a thin band that could affect the Royals game. Low: 47°
  • Wednesday: A 90% chance of rain near Kansas City. Nearly a 0% chance near the Iowa border. Amounts will range from none up north to over an inch south and east of KC. High: 49°
  • Thursday: Lingering showers. High: 63°
  • Friday: A week to two week dry spell begins with limited chances for rain. A warming trend into the 70s this weekend.

The mid-week weather set-up:

There is a very interesting set up for Wednesday as the next storm system develops and intensifies as it passes the Kansas/Missouri state line Wednesday. This is creating a tough forecast for tomorrow near Kansas City.

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This forecast map on the left shows the 500 mb level valid at 7 PM this evening. 500 mb is half way through the atmosphere in weight and we use this forecast level to track upper level storms and to find the cycling pattern. 0 mb is the top of the atmosphere as there is no weight, and 1,000 mb is the pressure near the surface. The average sea level pressure is actually 1013.25 mb, or 29.92″ of mercury. 500 mb is around 18,000 feet up.

On this map you can see a series of disturbances. There is a lead disturbance that will shoot an area of PVA (Positive Vorticity Advection) out over the I-70 region near Kansas City this evening. This will likely result in a narrow band of lifting which will result in clouds. During th
e winter this would likely be dry, but in the spring months this type of pattern has more moisture available and will likely result in an evening area of rain that must be watched for the Royals game tonight.

The disturbances will then carve out this developing storm by Wednesday:

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The faster this storm intensifies and closes off the more likely it will draw Wednesdays rain a bit farther north. The NAM out performed the other models this past weekend on rainfall amounts near KC, and it was the only model bringing the rain north of I-70 as of yesterday. The other models have caught on and this is why my confidence level of forecasting rain into Kansas City on Wednesday has increased substantially.

Rainfall Forecast Ending Thursday:

gfs_apcpn_scus_11

The Kansas City viewing area is forecast to have anywhere from not one drop of rain to over 2″ of rain. This is the GFS model that has trended north on every model run in the past 24 hours. Let’s see how this sets up and I will discuss this on 41 Action News tonight and on KSHB.com where you can always watch our forecasts and newscasts streaming.

How Did This Very Dry Weather Pattern Turn Wet?

Puzzle-2

The weather pattern is cycling as described by the LRC. The LRC is the centerpiece of this big atmospheric puzzle. There are other influences:

As I clearly showed in the video posted two days ago, the pattern that we just experienced is directly related to the pattern that produced severe weather outbreaks on January 2nd and February 28-March 1. These severe weather set ups occurred 57 and 60 days apart or 117 days after January 2nd was this past weekends stormy set up, roughly a 58.5 day cycle. What is next, the part of the pattern that blasted Kansas City’s viewing area with a severe weather outbreak on March 6th and Wednesday into Thursday is 58 to 59 days later.

How did the pattern suddenly turn wet in late March and April after it was so dry with a developing drought? The other influences have changed in the past few weeks. There may very well be an El Niño or ENSO (El Niño Southern Oscillation) influence. And, the AO and NAO have suddenly gone into negative territory, possibly deeper into the negative than they have been all season.

Screen Shot 2017-05-02 at 6.19.39 AM

As you can see above, the weak La Niña winter rapidly transitioned into the potential very early stages of El Niño. The forecast for where the ENSO index will go from here is certainly unclear. It appears it will either be a very weak El Niño next winter or neutral but on the El Niño side of the graph. When there is an El Niño the potential for a LRC trough over the western states near the Rocky Mountains or west of there is increased. This influence on the cycling pattern may be one of the reasons for the sudden shift into these stronger storm systems. Very important point here: The same pattern continues as shown in the video two days ago. But, these other influences may be the cause of the sudden production of rain, and so much rain.

The AO and NAO:

The Arctic Oscillation and the North Atlantic Oscillation also are indicators that influence the cycling pattern. While ENSO is an influence from the Tropical Pacific Ocean, the AO and NAO are likely influences north of the westerly belt. When the AO and NAO go deeper into negative territory, the jet stream can be energized and forced farther south. Both of these indexes are forecast to dip lower than they did during the entire winter.

ao.sprd2

nao.sprd2

These two influence on the overall bigger picture that we are sharing with you are likely part of the reason why it suddenly turned wet and very wet in the plains. It is not what I was expecting or forecasting. This is likely the cause.

The Month Long Forecast For May:

Well, how did we really do in this past month of long range forecasts?  Weather2020 made the very bad forecast of predicting the drought to grow, then April to have below average rain. WRONG! The critic will take these couple of bad forecasts and let us know over and over again.  This is the nature of what the weather forecaster has to deal with.  How about the NFL draft predictions. Do you realize that the best predictions were around 25% accurate. How about Baseball Perspectus.  They are right around 30% of the time. These are also future predictions and people are forgiving. I will stand behind our accuracy. If we are 60 to 75 percent accurate in the 20 day to 200 day range, that is actually very, very good. This is what we are doing here and sharing with you.

Now, here was a forecast I showed on the air 60 days ago. I found this graphic yesterday in my archives. I showed this on the air. There was severe weather each of these days, just not in Kansas City, which I always think is a good thing.

Have a great day bloggers. I hope this made sense to you. Watch 41 Action News tonight and I will go in-depth into our explanation of how this is setting up.

Gary

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