Monsoons and early morning weather in Tempe, AZ

Update

It has been a few weeks since I have updated this blog. To fill you in, my life has been crazy hectic! I recently moved to the sunny state of Arizona, and got a job as a Foreclosure Specialist at Nationstar. I have also found a great place to live and have been making new friends here in the valley. Arizona has turned out to be a real gem of a state. Such natural beauty, I can hardly wait to explore more of it once it cools down.

Monsoons and Weather

Naturally, coming from a weather background, I cannot help but notice all the weather that has been going on in the area. From torrential downpours, too extreme lightning, Arizona appears to be rich with weather activity. It is monsoon season! Scientifically speaking, monsoons are classified as a change in the predominant wind direction. There are two types of monsoons: dry and wet. Arizona usually experiences a wet monsoon. As you can see from the pictures that I posted, monsoons can have a big impact on the environment and us.

So what forces contribute to wind flow changes in Arizona?
How does the National Weather Service recognize when monsoon season has started?
Lets take a look!

Forces Contributing to Monsoon Season

In order to understand wind flows, you first have to understand thermodynamic principles. The laws of thermodynamics states that energy must flow from areas of high pressure to areas of low pressure. In meteorology, we are all about temperatures, dew points, densities, pressure, ect. So when we talk about pressure, we are really saying that areas of high pressure can be assumed to have cooler temperatures, and areas of low pressure can be assumed to have warmer temperatures. That is why in the summertime, it is always cooler on the floor of your home, and it is always hot towards the ceiling (hot air rises, cool air sinks. Think of the air as density). 

On a broader scale (scale, another important meteorology concept), Arizona begins to experience increasingly hot temperatures leading into the summer months. Factoring in what we learned earlier (hot air rises), a thermal low pressure system begins to develop over the Arizona region. This low pressure system is the beginning phase of the wind shift. As the low pressure system develops, the subtropical high pressure ridge pushes into the central United States. When this happens, we begin to see a change in wind flow. Instead of winds coming from the west north west, we begin to get a warm and moist southerly flow of air. Humidity (dew points rise) in the desert region increases significantly, and thus storms are able to develop. 

How to recognize monsoons and the National Weather Service's definition for monsoons

Recognizing the beginning of monsoon season is not rocket science. I'm sure all of us in Arizona are used to the 101 flooding or cars washing away. 

Diving into a more scientific approach, the NWS has stated that it classifies the beginning of monsoon season when dew point temperatures are above 50 degrees fahrenheit for more than 3 days. This illustrates that a direction change in the predominant wind has had a chance to impact the region. 

So lets take a look at current weather conditions (obviously we are in monsoon season, this is just to hammer home my point). This picture shows temperature and dew points (temperature being on top and dew point being on bottom).

As we can see, dew point temperatures are at 61 degrees. So we are still in monsoon season.

Just to further illustrate how well this works, the below picture is of a graph showing dew point temperatures and rainfall patterns in the Phoenix area.

Dew Point Temperatures:

Rainfall/Thunderstorm records:

Comparing the two graphs reveal that the higher percentages of rain and thunderstorms occur when the dew point temperatures are above 50 degrees.


To wrap things up, I hope you all enjoyed my insight into what monsoons are, the forces that drive them, and some defining meteorological characteristics. While everyone says forecasting for a desert is easy, it can still pose interesting weather situations. Thanks for reading!

Sources

http://insurancecompanyofflorida.files.wordpress.com/2012/06/flooding.jpg

http://www.thehindu.com/todays-paper/tp-national/monsoon-plays-truant/article2989193.ece

http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookener1.html

http://en.wikipedia.org/wiki/File:Monsoonmapb.JPG

http://azstarnet.com/news/local/woman-found-dead-in-car-swept-away-in-flooded-wash/article_6412e95c-f902-11e1-a103-001a4bcf887a.html

http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=12#

http://weatherspark.com/averages/30108/Phoenix-Arizona-United-States

Classification Methods Summary

For an advanced cartography class, I compared poverty to education through four different classification methods. The expected result should show high poverty in locations with no advanced background in education and low levels of poverty in locations with advanced backgrounds in education. After displaying the results, we can see that locations with low education do not always correlate to high poverty. A good example of why this correlation is skewed, is due to large cities. The diversity of cities such as Phoenix, or Tucson, skews the data.

Cartography Update 3

Proportional Symbols - Proportional symbols are a good method to use when trying to convey data in relation to different size shapes. The most convenient shape to use is the circle. The circle is hailed as the most stable shape when increasing size. However, the average person viewing a map based on circles will lose up to 50% of the geometric size of the circle when looking away leading to over/under compensation of circle size. This can lead to problems if you choose the incorrect way to size the circles for your map. There are essentially two methods used to create these symbols; Mathematically (poor choice) and Perceptual (good choice).
If the map is done through mathematics to come up with circles that are doubled in area size, then it becomes very difficult to decipher which circle is which (See map below).

Especially in the higher classes, it is impossible to tell which circle is which when looking on the map.


Now if the map is based on the perceptual circles, which actually look twice as large, it becomes much easier to tell which circle is which on the map (See map below).

This allows for the viewer to decipher which circle is which and even switches around the circle arrangements somewhat on the map itself. (Side note, the map above is a bivariable map. Meaning that it displays two forms of information. A choropleth, which shows population per state, and the proportional symbols which show number of EPA sites per state).

Flow Map - Flow maps are used to represent a movement of some object from one place to another. These maps can be very difficult to do. The first step to do is to determine the width of the line for each data group you represent. You can this by:
1.) Sort the data into several groups based on a certain geographic trait
2.) Then calculate each groups percent contribution to the total number
3.) visually represent each group by plotting them on a graph
4.) using natural breaks, group each dataset into a cluster of groups
5.) using a maximum line width (usually 80-90pts.), multiply the percentage of each cluster by the maximum line width then divide by the number of elements in that cluster
6.) Repeat for each cluster, then design the legend based on the numbers calculated from step 5

The flowing is an example of immigration to Canada from surrounding countries