The Weather Wire
July 2005 Volume 13 Number 07
Avg High 81.1
Avg Low 50.8
Snow - 0.0"
Season Snow - 39.3"
Precipitation - 3.99"
Avg High 88.0
Avg Low 58.7
Avg Snow - 0.0"
Avg Precip - 2.16
Latent Heat Energy|
Here it is July and the peak of thunderstorm season. July has more thunderstorms than any other month of the year. If you have been watching the TV weather or read the forecast discussions that appear at the top of your daily forecast from us, you no doubt have heard the reference to dew point and or relative humidity and the chances for thunderstorm activity. The higher the dew point and humidity the better the chances for showers and thunderstorms. Once the dew point goes above 50 along the Front Range, chances increase significantly for heavy to severe thunderstorms. Other than the fact that higher humidity means there is more moisture to work with, why does increased moisture mean bigger more severe storms?? It all has to do with ‘Latent Heat Energy’.
Latent heat energy is the heat and energy stored in water vapor. Water vapor is the gaseous form of water. Now most of us are familiar with the liquid form of water, we see it every day in our rivers, lakes and streams, not to mention at home when we turn on the faucet. To get liquid water into the gas form all we have to do is heat it. In other words add energy to it. It's as simple as boiling water, we add heat to it, it boils and turns into a gas, if we leave the heat on long enough all the liquid water will be gone. We have added heat energy to the water vapor. Outside of the house it is not necessary to boil the water. Water evaporates all the time from lakes, rivers even from your backyard. It still takes the same amount of energy input to transform liquid water to gas. And the water vapor stores this energy until it returns to a liquid form and releases this stored heat.
This is where showers and thunderstorms come in. As the sun heats the surface areas around us the land areas heat up the surrounding air. Warmer air is lighter and begins to rise. As this air rises it cools and at a certain point it reaches a point where the water vapor turns back into a liquid. The air has reached saturation point. As meteorologists we call this the liquid condensation level. This can be thousands of feet high or right at the surface (fog) depending on how much moisture is in the air and the actual air temperature.
When water vapor returns to the liquid state it gives up the heat energy that turned it into a gas to the surrounding air. This in turn allows the developing storm to grow even taller and stronger as this heat energy is added. So the more water vapor that is converted to liquid in the form of clouds and rain the more energy the developing storm has to work with.
Here along the Front Range we as a general rule are pretty dry. For example. today, July 6th, DIA has a dew point of 35 and a relative humidity of 13%. So pretty dry! To the east in Limon the dew point is 55 and the humidity is 35%. This is typically the case, moisture tends to increase the further out east onto the plains you go. So that any storms that form along the Front Range will stay pretty weak, with gusty winds, some lightning, but little in the way of rain, until they tap into the higher moisture levels to the east and the higher energy levels stored in the higher levels of water vapor to the east. Only when the higher moisture levels make it all the way up to our Front Range will we get the severe thunderstorms.
So there you have it, actually pretty simple, the more available moisture the more heat energy a developing storm can tap into and use. So the next time you hear a reference to a high humidity day you will know we have a better chance for some heavy to severe storms.
Online Forecasts Available Again
Skyview Weather is happy to announce that online forecasts and snow reports are again available on our sister www.anythingweather.com website. Forecasts and snow reports are password protected, but an email to Tim@Skyview-WX.com requesting your forecast and/or snow reports be available online will result in an account being setup for you. As always, forecasts and snow reports are for client use only, but with the online access, forecasts and snow reports are just a click away from any computer with an internet connection!
Little change in drought conditions across most of Colorado, with few areas of drought remaining..
The map below shows forecasted temperature deviances for July 2005. As can be seen, normal temperatures are expected for much of Colorado for July 2005, while a portion of Northwestern Colorado is forecast to have below normal temperatures..
The map below shows forecasted precipitation deviances for July 2005. Normal or near normal precipitation is expected for much of Colorado for July 2005, with the exception of far Southwest Colorado where below normal precipitation is forecast.
As can be seen in the below map, most of the state has come out of the widespread drought conditions of a year ago.
June 2005 became Denver’s 4th wettest month With 3.99 inches of rainfall that pushed us 2.43 inches about normal for the month. Our yearly total is now 8.13 inches which make us right about normal for the year. Normal for the year is 8.09 inches. Again remember that during thunderstorm season rains can be very spotty. For this month DIA just happened to be under a couple of good storms. Also as proof that it was a pretty active month we saw 17 thunderstorm days during the month of June.
The average temperature during June 2005 was 66.0 degrees which is 1.6 degrees below normal. It was a generally pleasant month, with 7 ninety degree days, which is only 1 above normal. Temperatures during the month ranged from a high of 93 degrees down to a low of 39 degrees. Only one temperature record was set, a record high minimum of 66 degrees on the 21st, breaking the old record of 65 degrees last set in 1988.
Denver’s weather is notorious for being changeable. However this is not the case during July. Most July mornings are sunny with clouds developing during the late morning and early afternoon. By mid-afternoon, thunderstorms develop over the foothills and drift across the Denver metro area and then onto the eastern plains. Some of these storms continue to develop and reach severe status. Severe thunderstorms containing large hail, strong gusty winds and heavy downpours are not uncommon during July for the Denver metro area.
The worst hailstorm on record in Denver history moved across western sections of the city on July 11th 1990. This ferocious storm dropped baseball to softball sized hail and caused millions of dollars worth of property damage. July is the stormiest month of the year with thunderstorms occurring about every third day or usually 11 days per month. Most of the rainfall during the month is the result of slow moving thunderstorms which can cause precipitation to vary tremendously at different locations across the metro area. It is not unusual for some areas of the city to receive two or three times as much precipitation as other areas. Flask flooding is also quite possible during July.
Sunrise/Sunset (Denver area)
May - June 2005