Relative Humidity and Dewpoint

Tuesday, October 2, 2017 provided an excellent example of why meteorologists turn to dewpoint temperature to get a better picture of moisture in the air. Relative humidity is a good index to monitor drying potential, disease potential, or fire risk, but relative humidity is relative to the air temperature. When the air temperature changes, the relative humidity changes. Dewpoint temperature is an absolute measure of water vapor, independent of air temperature.

Wheat dew on heads(2)

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Cool August Slows Cotton Maturity

Friday morning has arrived and so has another rainy August day in Oklahoma. All the rainy days this August has meant more cooler days. Those cooler August days have left cotton farmers wondering if they’ll have enough heat units to fully mature this year’s crop.

One of the ways to track a crop’s daily and accumulated heat units is with the Oklahoma Mesonet Degree-day Heat Unit Calculator. This tool allows you to enter a crop planting date and get a table of heat units for any Mesonet site. The table shows daily heat units from planting to the most current date and the accumulation of those heat units over the season.

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Inversion, Dispersion and Spraying

You’ve got a busy day ahead! If part of the day’s work is spraying, it’s tempting to kick on the sprayer as the morning sun lights up your crop and soil. If you’re spraying a herbicide, you don’t want to spray when an inversion is present.

Morning mist is a visible indicator of an inversion, but don’t assume an inversion is gone. The mist maybe gone, but  inversion may still be in place. Read on for a sure way to know when an inversion has fully dissipated.

morning-mist-wallpaper-c2017-08-08.AgBlog.Inversion Dispersion.Morning Mist Soybean Continue reading

Pecan Scab Attack

When warm nighttime temperatures overlap times of high moisture, pecan scab spores have a good environment to commence their attack. In Oklahoma, we often see these weather conditions in late May and early June.

2011-06-21.Pecan scab.leaf.stem.William Reid.Northern Pecans

(Photo: Leaf with pecan scab (William Reid/Northern Pecans)

Spores released in the spring can infect leaves and young stems. This begins the growing season cycle of pecan scab infection. Spores germinate to enter tender leaf, stem, and nutlet tissue. Fungal hyphae grow inside leaves and stems to produce more spores that infect more leaves, stems, and nuts. Continue reading

Beaver 2017, Too Long Between Rains

Western Oklahoma’s latest rain was critical to the success of this year’s winter wheat and canola crops. It also brought much needed relief to fire fighters as it drenched areas where large, devastating fires occurred in early March. The rain came with storms on March 28-29, 2017.

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If we just looked at rainfall totals, we’d be hard pressed to believe that 2017 is dealing with “dry” year conditions. That’s because rainfall totals since January 1st fail to tell the story of real-world conditions. One has to drill down and scrutinize rainfall totals under the microscope of daily rainfall events and amounts. And the Oklahoma Mesonet has just the tool to do that, the Mesonet Long-Term Averages Graph maker.  Continue reading

Wind’s Weather Role in NW Oklahoma Complex Fires (part 3 of 3)

The stage was set. The players for a drama of tragic proportions assembled. Two leads waited their cue. Already on stage were fine dead fuels from previous growing seasons, low moisture in February, and super low humidities. The next player in the drama entered, high wind speeds. This article is part 3 of 3 articles exploring weather conditions that set the stage for the Northwest Oklahoma Complex Fires that broke out on Monday, March 6, 2017.

2017-03-16.1Mb.Fire wall behind field and farmer.Terena Burke Bridwell.Barby Ranch.The Oklahoman

(Photo: Terena Burke Bridwell/Barby Ranch Beaver County)

At 11:00 AM March 6th winds across Beaver County were out of the southwest. Wind speed at the Oklahoma Mesonet Beaver site was 37 miles per hour. Continue reading

Relative Humidity’s Weather Role in NW Oklahoma Complex Fires (part 2 of 3)

As relative humidities drop, standing, dead plant stems dry out. Dense, dead, dry grasses were the primary fuel source for the devastating fires that flared up on March 6, 2017 in Oklahoma, Kansas, and Texas. This article is part two of a three part series. It covers the relative humidity conditions in Oklahoma leading into this horrendous fire day.

AgBlog.Fire and dead grass.Kathy Larson and Joe Coffey.The Cayenne Room.Oregon (1)

March kicked off with relative humidities unusually low across Oklahoma. Continue reading

February’s Weather Role in NW Oklahoma Complex Fires (part 1 of 3)

Intense, devastating fires flared up one week ago in Oklahoma, Kansas, and Texas. This article is part one of a three part series. It covers the long-term conditions leading into this horrendous fire day. Part One covers weather factors in February that contributed to extremely dry conditions in Beaver, Harper, and Woodward Counties.

2017-03-07.NW OK Complex Fire.fire and truck line at night.Carmen Fire Dept 2

(Photo: Carmen Fire Department 3/7/17)

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