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Joe’s Weather Blog: Strong early September front in KC + Irma (SUN-9/3)

Hope you’re having a good Labor Day weekend…it feels like the swan song of summer out there now and it should get hotter Monday as a strong (for September) cold front moves into the area. The timing of that front will play a role in how hot we get…slower and Downtown KC could make a run towards 95°…faster and the temperatures will be about 5° “less hot”. Interestingly…not a lot of rain is expected with the passage of the front. There will be a chance of storms, but the better chances may reside towards the south of KC. Then MUCH cooler weather will move into the region overnight into Tuesday…and highs on Tuesday may struggle to get into the 70-75° range.


Forecast:

Tonight: Clear skies and mild with lows in the 60s

Monday: Mostly sunny and hotter with highs in the upper 80s to lower 90s. There may be some late day storms developing as the front moves into the area…especially from KC southwards and into the MO side of things

Monday night: Clouds around with cooler air moving in and a chance of showers.

Tuesday: Cooler with morning rain chances fading then partly cloudy skies with breezy conditions and highs 70-75°


Discussion:

This week will feature two contrasting air masses. The hotter air moving in on Monday and the the reversal towards MUCH cooler weather for Tuesday>Thursday. The week overall will be dry…and IF we miss out on the decent rain with this transition…many very well may, there isn’t much rain coming, if any, for another week or so. It’s been a while since the grass needed a good drink of water…we’re getting there now it appears.

The cold front in question will be moving into the region tomorrow afternoon/evening. Ahead of the front we’ll heat up…near to over 90° highs are VERY possible, especially from KC southwards…farther north it may be a bit cooler. These fronts typically have storms/rain moving with them, especially considering the timing is good for convection. There will be a lot of instability out there BUT with the winds ahead of the front mostly from the SW direction and the winds behind the front from the NW direction…there isn’t a lot of convergence occurring.  with all of that said it makes me a bit nervous to take storms out of the forecast for later tomorrow afternoon/evening. Fronts like this SHOULD have storms with them even with a lack of convergence considering it’s coming through during the ideal time to generate storms in the area.

Bottom line…storms are possible after 4PM from KC southwards…

Not much else is expected after that for the rest of the week. Cooler air will spread into the area and we’ll need to watch the record low of 43° (1988) on Wednesday morning and 47° (1986) on Thursday morning especially. Regardless it will be about 10-15° below average for several days. As a matter of fact the NAM model would suggest the potential of some patchy frost across N MO towards the IA border IF the winds were to drop off.

Morning lows Wednesday…IF this is right…we get a record low!

So aside from the cooler weather…not much else to talk about beyond that in KC for awhile.

Irma:

Continues to go through weakening and strengthening phases as the core winds increase and decrease some 10-20 mph or so when the phases occur. It appears it may be trying to strengthen again on the satellite pictures. The images below are the infrared shots so look for the darker blacks and expanding reds indicating the colder and taller cloud tops around the center of the storm.

Irma is moving more towards the west it appears…and it’s still around 900 miles away from any land areas. This westwards movement was not necessarily expected today…there was an expectation that a more WSW movement would occur for a longer period of time. The more west movement, in a sense, is interesting as this may reduce the overall threat to the Caribbean Islands.

It’s NOT a particularly BIG hurricane and the winds around the smaller core are the main concern right now. IF you have travel plans towards the Caribbean or the Puerto Rico area…this next map showing the arrival of 39+ mph winds may be helpful.

In terms of positioning and strength…

The time frame that the USA starts to worry about is towards next weekend. Notice the forecast position on Friday…in the far SE Bahama Islands towards the Turks and Caicos Islands.

There are some 700 islands in the Bahamas of which about 30 are inhabited.

This region will be under the gun potentially towards the end of the week. From there it’s more complicated although IF the storm is still moving NWards…the chances of a US landfall will increase and the modelling has been strongly suggesting that areas from FL northwards to the Carolina’s especially will need to watch this storm for later next weekend and early the following week.

Some meteorologists like to show on TV the “spaghetti” models forecast. This is a run of many different GFS model ensembles with various pros and cons to their physics. I don’t like to show them on TV because I think they’re confusing to see and understand in that format…however on the blog they’re perfect. Basically we look at these to see if there are commonalities in forecast tracks especially. When the models diverge considerably, which typically happens the farther out in time you go…that leads to lower confidence…when the model track forecasts are more overlapping…higher confidence. The BLUE line with circles represents the GFS model run that many weather folks are familiar with.

Then there are the tropical specific models that are run..again there are pros and cons to these model forecasts as well. Some models take into account some things but not others. Some models are strictly based on climatology and statistics.

The smaller numbers…24, 48, 72, 96, 120, 144, and 168 represent the forecast position 1,2,3,4,5,6 and 7 days out.

So you can see the concern for the Bahamas…and the concern developing for the SE US.

The latest EURO model has the hurricane several hundred miles off the coast of central FL next Sunday evening. It’s being blocked according to this model from moving northwards because of higher pressures across the NE part of the country…so it really has nowhere to go on that model. Of note as well is that there is a LOT of warm to very warm water down there and that will provide “gas” to the hurricane engine as we get through the end of the week. This is measured in heat potential and is shown below. Notice where the hurricane is now…there isn’t a lot of heat potential to feed off of…maybe part of the reason why it’s in “maintain” mode and not able to sustain any strengthening.

As Irma gets into the SW Atlantic Ocean towards the Bahamas…it’s going to get a shot of “premium” gas.

This is why we’re expecting some impressive strengthening of the storm over the next 5 days or so.

The takeaways…

  1. Still wayyyyy to early for the folks in FL to NC to be freaking out about this storm. although they’re being urged to prepare as they should since we’re coming into the peak of the season anyway. Easier to get stuff now as opposed to next weekend.
  2. We do expect, at the very least, the Bahamas to have issues with the storm
  3. The Gulf of Mexico has a lessor chance of being affected by this system however it is also still on the table based of some data today.
  4. IT’s still possible that the core of Irma remains totally offshore and doesn’t directly hit the US coastline at all although there will be high surf/waves battering the FL coast regardless next weekend and then the Carolinas early the following week.
  5. It’s still worth monitoring because there are many variables that will be changing over the next 5-10 days.
  6. A recon mission into the front side of Irma is scheduled for later this afternoon…so we may get at least a better idea of the storms health then
  7. IF you have vacation plans towards the SE US next weekend OR into the following week (the 11th) please pay attention to the forecast of Irma.

Our feature photo comes from Glenna Oidtman

Pretty!

Joe

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