Summary of this post, if you don’t want to read everything(tl;dr):

• Tuesday 8/9/11 will be the hottest day of the next week.
• No rain in the forecast the next 7 days.
• We will likely break the record of most consecutive 100+ degree days this Friday, at 42 days.
• Possible cold front this upcoming weekend, may lower afternoon highs below 100 degrees finally.
• High afternoon temps and high overnight lows placing energy grid on exceptional load.
• Worst one year drought in Texas’ history expected to persist or worsen the next 1-2 months.
• Expect above average temps and below average precipitation through spring 2012!
• Tornado risk may be increased early spring of 2012.

Weather details the next seven days:

Currently, the dominant high pressure ridge across the region is expected to persist and possibly shift to our west slightly. A broad upper level low will develop across the eastern U.S. later this week. A weak cold front is expected to slide down from Kansas on Tuesday, and stall out along the Red River. Some scattered afternoon thunderstorms are expected along and north of this cold front. Unfortunately no convection is expected to slide across the border into north Texas, and the region should continue to remain rain free.

The presence of this cold front however is expected to generate enhanced subsidence to it’s south, and increase daytime highs. Tuesday high temperatures for far northern north Texas will likely reach 110 degrees, while the Metroplex will be around 107 to 109. Tuesday 8/9/11 will likely be the hottest day of the entire week here in Dallas/Fort Worth.

The rest of the week, high pressure continues shifting to our west and our daytime high temperatures will decrease slightly. Highs are still expected to remain above 100 through the end of the week, so we will very likely break the 42 consecutive day record set back in 1980. No rain is expected in the Metroplex or north Texas (except for immediately along the Red River on Tuesday) through Friday.

The next weather system to watch for is coming up this weekend. Depending on the location of this high pressure ridge, we may see a cold front move through the area and have daytime high temps finally drop below 100. I use the term ‘cold front’ loosely however. Currently I don’t see any rainfall expected with the cold front. It is still a week away however, so that forecast could change.

What makes this heatwave especially difficult?

Meteorologists use a figure called Degree Days Cooling and Degree Days Heating to determine approximate energy usage based solely on outdoor air temperature. This takes an hourly temperature difference from the baseline of 65 degrees, and averages it out across 24 hours. The final number can provide an estimate of how much energy was utilized in that period to cool or heat buildings. 65 degrees is used as the baseline, as this is usually the threshold where households switch from cooling to heating. The closer to 65 degrees, the less climate control energy is used.

Typical summer afternoons in Florida would average anywhere from 17 to 20 degree days cooling(meaning, the day’s 24 hour temperature averaged 17 to 23 degrees warmer than 65). The last several weeks here in north Texas, our Degree Days Cooling have averaged at 30.

This number is very high because our overnight lows have remained quite high, throwing the average up. Days with 30 degree days cooling or more put an exceptional load on our power grid, and can result in rolling blackouts during peak energy consumption (around 3-7pm local). This has also prompted the National Weather Service to continually keep heat advisories or excessive heat warnings issued for the entire region for several weeks in a row.

This extreme heat event, coupled with the worst one year drought ever experienced in the state of Texas, has made this summer exceptionally bad. Wildlife, plant life including crops, even our own hydrological needs with area lakes as our water reservoirs are strained quite severely. This takes me into our long term outlook…

Long Term Climate Outlook:

As you can see, the only area of the state that is not currently under a drought is a very tiny plot of land in extreme coastal south Texas. Otherwise the entire rest of the state is under some type of drought conditions. The area around the D/FW Metroplex continues to worsen, with us now in a D2 or worse drought status.

These drought conditions are considered the worst one year drought in Texas’ history. These conditions were brought on by a natural cycle in the tropical Pacific ocean known as La Nina. Cooler than average sea surface temperatures begin a chain reaction of events in our atmosphere, that eventually lead to storm systems tracking much further north in the United States. This brings less precipitation to the southern states along with higher than average temperatures.

Current long term forecasts from the Climate Prediction Center indicate at least another 1-2 months of above average temperatures and below average precipitation. Month 3 still shows above average temperatures, but equal chances of above/below average precipitation. Month 3 puts us in the October/November time frame. October is historically the 2nd rainiest month for north Texas, behind May.

Currently the ENSO (El Nino Southern Oscillation) shows neutral to possibly very weak La Nina conditions. Overall the atmosphere still indicates a La Nina type of pattern. The Climate Prediction Center also estimates now through early winter that the ENSO will remain neutral. In mid to late winter, weak La Nina will likely re-develop.

In north Texas, this means we should continue to expect above average temperatures and below average precipitation now through at least early spring of 2012!

How does this impact tornado forecasts next year?

ENSO has a less direct influence on tornado genesis and behavior. Various research papers have been written studying the relationship between the two, and just as many opinions have been formed about the relationship.

One paper published in 1999 by the Storm Prediction Center indicates a weak correlation between La Nina months and increased tornado frequency(source: Storm Prediction Center). Another paper published on behalf of Colorado State University in 2005 shows higher than average number of tornadoes, more violent tornadoes, and higher risk of tornado outbreaks during strong La Nina years (source: link).

For reference, winter and spring of 2011 was classified as a strong La Nina event. The research paper published on behalf of Colorado State University seems to correlate to the actual observed events well.

The next most recent weak La Nina event was during Winter season of 2008/2009. During that winter, numerous tornadoes developed in the southern plains including the first deadly tornado of 2009 in Lone Grove, OK.

This winter we can expect very similar conditions, a weak La Nina developing mid winter, and possibly reverting to a neutral pattern afterward. If we use history as any indicator, this means the southern plains including north Texas may have above average tornado potential in late winter/early spring.

This is of course strictly my opinion based on my experience and using history as a guide. Use this information for your reference if you so desire.

That’s all for this post. North Texan’s, keep cool and keep safe out there!

You may also be wondering when is it going to get real cold here? Well nobody knows for sure, but when you consider weather history from years past, the answer would be ‘soon’. According to the National Weather Service, DFW Airport’s average first freeze date is November 22. This, coupled with this years climate forecast indicating above average precipitation and normal or slightly below normal temperatures, might indicate that we can expect our first freeze within the next two to three weeks. Below is a graph of the average freeze days recorded per month from DFW Airport. You can see that December and January will likely be the two coldest months of the season.

For more information including seasonal averages and extremes, see the Freeze Summary for DFW Airport, provided by the National Weather Service.

As a side note, Tropical Storm Ida is about to make landfall in Mobile, AL with 60mph winds. The storm encountered strong upper level wind shearing and cooler gulf water temperatures and lost a majority of its strength prior to landfall. There is still some minor flooding occurring along several southern Alabama and extreme western Florida panhandle counties. Additionally high street flooding and 5 foot storm surge is reported in eastern New Orleans in areas outside the hurricane flood control system. This storm is forecast to make a right hand turn and dissipate within 36 hours.

Looking at the Climate Prediction Center’s 6-10 day and 8-14 day forecasts, north Texas can expect more above average temperatures and below average precipitation. Keep in mind these forecast begin 6 days out, which will be after the rain event we will encounter the next several days. Beyond that, El Nino conditions tend to create warmer than average, as well as stormier than usual conditions for north Texas in the Winter.

Below is a small list of reports that NOAA, the National Weather Service, and AccuWeather have put together regarding recent observations where weather conditions have departed from normal.

El Niño Arrives; Expected to Persist through Winter 2009-10

El Niño’s impacts depend on a variety of factors, such as intensity and extent of ocean warming, and the time of year. Contrary to popular belief, not all effects are negative. On the positive side, El Niño can help to suppress Atlantic hurricane activity. In the United States, it typically brings beneficial winter precipitation to the arid Southwest, less wintry weather across the North, and a reduced risk of Florida wildfires.

El Niño’s negative impacts have included damaging winter storms in California and increased storminess across the southern United States. Some past El Niños also have produced severe flooding and mudslides in Central and South America, and drought in Indonesia.

An El Niño event may significantly diminish ocean productivity off the west coast by limiting weather patterns that cause upwelling, or nutrient circulation in the ocean.  These nutrients are the foundation of a vibrant marine food web and could negatively impact food sources for several types of birds, fish and marine mammals.

NOAA: Global Ocean Surface Temperature Warmest on Record for June

The world’s ocean surface temperature was the warmest on record for June, breaking the previous high mark set in 2005, according to a preliminary analysis by NOAA’s National Climatic Data Center in Asheville, N.C. Additionally, the combined average global land and ocean surface temperature for June was second-warmest on record. The global records began in 1880.

Climatology of Hurricane Seasons with a Late Start – By NWS WFO Ruskin

As expected, there is no major correlation to a late start to the season and characteristics of the season. Several seasons saw 10 or more TCs form with 5 or more landfalls, while other years saw 4 or 5 storms form with just a couple landfalls.

3,000 Low Temp Records Set This July! – By AccuWeather.com

1,044 daily record low temperatures have been broken this month nationwide according to NCDC — count record “low highs” and the number increases to 2,925, surely to pass 3,000 before the end of the month.