Warm Air... and Waiting...

Last blog, we wrote about how we were riding a ridge of warm air northwards.

For a Canadian in March, warm air is usually a welcome and much anticipated change. All of us know that warmer temperatures will bite into the snowpack, and hopefully do some serious damage to a winter's worth of accumulated snowfall.  

However, warm air can also create some problems... and a special set of challenges for those of us who fly.

Technically, it really isn't the warm air that creates all of the trouble. When we were in Arizona, we had plenty of warm air. The flying was great! You may remember a spot two blogs ago where we mentioned that that visibility was at least 200NM! This is a high standard for someone who flies by way of visual references to the horizon like we do. 

So then, why the sudden change? Why do we now barely see across the street, and suffer with clouds that at best scrape along the tops of the telephone poles?


In a word, moisture.

You see, this parcel of air that we have been following since yesterday was sent northwards on giant a conveyor belt--one that starts somewhere in the Gulf of Mexico. The Gulf is one of the most powerful generators of warmth and moisture on the planet, and boy has it been pushing truckloads of it north over this past week. Although it may be hard to believe, a lot of the foggy stuff that we have seen the past little while has originated in the deep south!

Meteorologists call such a mass of air Maritime Tropical. Like a sponge full of water, it is sopping wet, and it starts out warm just like it has come freshly out of the washbucket. When we have a pattern and winds aloft that are ridging in weather speak, then we have the mechanism to send all this air northwards into the chilly plains of the North American continent.

Just think, right now there is a taste of Louisiana, Mississippi, and Texas for y'all! 

However, all this sopping wet stuff leads us to a particular challenge. Of course, these warmer temperatures will bite into the snowpack. This does give those of us a reason teo cheer... Winter is abating!

But...

This eating away of the snowpack also comes at a heavy cost to someone who hopes to get airborne. Flyers by way of Visual Flight Rules beware, for difficult things such as fog, low ceilings, and impossible visibilities may well be headed your way.

Why?

Well, warm air when put together with moisture exacts a price. Down in Arizona, the air contains little moisture. We were in the desert! However, now that we have put a lot moisture into the mix, it is going to cost us. In fact, we are charged not once, or twice, but THREE times  in the scenario that we are now facing as we wait with low ceilings and heavy fog in Nebraska.

For a moment, imagine a hot muggy summer day. (Remember, such days are not all that far away!) Next,  imagine a cold beverage of your choice as you sit out on the patio. What happens to that beverage as it sits in the sunshine on that patio table? We all know that the outside of that can or glass will appear to magically collect water, and that it will start to bead up with droplets of moisture. Companies like Pepsi, Coke, and many others take great pains to market their beverages with just such a picture. What could be more refreshing? 

This, then, is the first charge that moisture exacts. Take warm moist air, pass it on over top of something cold... (whether it be a snowpack or one's cold beverage!) and the moisture will then get all "wrung" out of the air and turn into something that we can see... fog and cloud. It becomes moisture in a visible, palpable, and tangible form, instead of the hidden form that was in before cooling. 

For those of you who have paid attention in ground school, you will recognize that something meteorologists call advection fog has just been described. This is not at all good if you are planning on flying... or for that matter, driving down the highway!

If this isn't bad enough, then allow me to describe the second charge that this moisture will levy on the aviator.

To understand this one, it is probably best that you think of nice hot shower. As one scrubs themselves clean, the showerhead pours vast quantities of moisture into the surrounding air. Eventually, the air becomes as full of moisture as it can possibly be moisturized, and reaches a point called saturation. We see this as fog.

It may be hard to visualize, but that snowpack that is melting is behaving much the same as the water that pours out of your shower head. Both methods are adding moisture to the surrounding air, and we will see the results of maximum moisturizing  (or more correctly saturation!) as fog.

The final and third part of this moisture trouble is related to lift. If one lifts air, it cools. As we found out through our beverage example earlier, cooling moist air leads to trouble. Lifting air causes it to cool, and when we do this it will eventually condense and create visible moisture.

Some of the best lifting agents in nature are related to low pressure systems and their associated fronts... and this is exactly what we were flying towards today! A huge and relatively stagnant low--one that doesn't move much and has little upper level support--is currently sprawling across the prairies of the North American Continent. (Meteorologists like to call what we have right now a "Closed Low") 

It isn't moving much.

It just keeps on sucking moisture up from out of the Gulf... warming the snow and adding moisture to the already sopping wet sponge... cooling it slightly as it runs across that same snowpack, and getting lifted as it slowly swirls into a Low of Continental Proportions.

So then, we are not moving much.

As this is being written, we are currently in North Platte, Nebraska. An early start out of Hugoton allowed us to ride a beautiful jet of clear, warm air towards home. The snowpack was non-existant in these more southern parts of the continent. The center of the Maritime Tropical Airmass was centered over the Oklahoma Panhandle. You can imagine that in Hugoton there wasn't a significant way to cool this warm, moist air that was rushing Northwards.

About halfway to North Platte, the skies were still clear. Enjoying the view, and having skipped breakfast to get out early, we remembered that we had some pizza onboard left over from last nights dinner. We enjoyed a hearty airborne breakfast.

It wasn't long before things started to change.

As we approached North Platte, however, we were nearing the snowpack and the low. Breifers warned us that IFR was only a few miles to left and a few miles to the right. We did not need to be told this, as we could very clearly see it. Things very quickly started to take a turn for the worse. We could actually see the moisture and clouds in the air to the left of us and to the right of us. It was almost like the biblical crossing of the Red Sea.

The lowering ceilings and decreasing visibilities caused us to carefully check the weather ahead as we stopped in North Platte. Could we continue?

Unfortunately, no! Ceilings ahead of us were only 200-300ft. Visibilities were reported to be 1/4 mile in snow and/or freezing rain. Not a good mix for a VFR pilot, and even many an IFR pilot would shudder with such conditions! 

We waited the rest of the day... hoping for some sort of a break in the weather and the ability to work northwards... however, a solid wall of low ceilings and visibilities held us at bay. We finally gave up our vigil at the airport around 7PM and got a shuttle into town for a stay.

Oh... and what did we have for supper? Well, right across the street from the hotel there happened to be an Applebee's...

And it most certainly wasn't McDonald's!