Updraft Category Archive: dew point

Cooler with scattered thundershowers, freezing rain possible northeast Minnesota

Posted at 6:38 AM on March 26, 2012 by Craig Edwards (0 Comments)
Filed under: Freezing rain, Rainfall, dew point

Yesterday's maximum temperature topped out at only 35 degrees at International Falls, which was four degrees below the average high of 39. The high on Saturday at the Falls was 58 degrees. In the Twin Cities the afternoon temperature failed to reach 60 for the first time since we settled for 52 degrees on March 12th. It was a good run well above normal temperatures.

Clouds are expected to prevail today. The maximum temperature in the Twin Cities may struggle to reach 50 degrees with periods of showers and thundershowers. Showers and thunder spread from central to northern Minnesota this evening. Many places are still short of precipitation for the month of March.

Here's a look at the potential precipitation totals for the next couple of days.

Due to the low dew points expected to hold over northeast Minnesota today and tonight, some of the precipitation is likely to occur as freezing rain. A Freezing Rain Advisory has been posted for a sliver of the Arrowhead Region for tonight. Freezing rain will coat tree limbs and pwer lines during the cover of darkness.

Details can be found by clicking on this statement from the National Weather Service in Duluth.

Strong winds are on tap as a low pressure system winds up over the upper Midwest later today. The National Weather Service has issued a Wind Advisory for portions of western Minnesota, where gusts could top 35 mph. Brisk winds are expected across much of the state on Tuesday as well.

The NAM depicts a strong surge of warm air as the low tracks towards International Falls at midday on Tuesday. This pressure pattern illustrates the potential for wind gusts to 40 mph in southern Minnesota.

It appears the trend continues to be our friend as we head into April. NOAA's Climate Prediction Center posted their April temperature outlook earlier this month. They sometimes refresh this outlook on the last day of the month.

Precipitation outlook from NOAA for April.

The normal maximum/minimum for the Twin Cities on April 1st are 50/31 degrees.
CE

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Warmth of August sun, minus the humidity

Posted at 4:30 PM on August 2, 2011 by Craig Edwards
Filed under: Climate, Hurricanes, dew point

I spent a couple hours outdoors this morning and it sure felt warm in the August sunshine. With only a slight cooling breeze it was a blessing to have dew points some twenty degrees lower than Tuesday. The dew point at the Twin Cities International Airport was 74 degrees yesterday and a more comfortable 55 degrees this afternoon.

While the mercury has climbed to ninety degrees or better at MSP this summer season on fourteen days, we are looking at a period out a couple weeks were it may be more to our delight with regard to heat. The average temperature for July in St. Cloud was about 4.5 degrees warmer than normal. The Twin Cities average temp was 5.6 degrees above normal for July 2011.

We have turned the corner for "normal" maximum temperatures in the heart of summer and are slowly creeping down into the lower 80s. By the time we reach August 13th the average high in the Twin Cities is down from 84 to 81 degrees. The 8-14 day outlook from the Climate Prediction Center depicts odds favoring at or somewhat below normal temperatures for the upper Midwest.

Check out the July climate reports for St. Cloud, Minneapolis/St. Paul, Eau Claire and Chanhassen here.

In case you think we had it bad here, and we did with the high dew points, the average maximum temperature for July in Dallas, TX was over 101 degrees. More than 70 percent of Texas is in an exceptional drought. They could use a decaying tropical storm to move inland and dump generous rainfall. That doesn't appear likely soon.

Keeping an eye on Tropical Storm Emily and the computer generated track is the challenge for hurricane forecasters in NOAA's Hurricane Forecast Center.

Here's the link to follow the tropical storm's the reminder of the season. NOAA's Hurricane Center website.

The latest update on the storm named Emily predicts a path that takes it over Haiti with winds of 50 mph and rainfall of over five inches. From the Hurricane Center's most recent statement this afternoon....Tropical Storm EMILY Public Advisory:
RAINFALL...EMILY IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
OF 6 TO 10 INCHES IN PUERTO RICO WITH ISOLATED AMOUNTS OF 12 INCHES.
RAINFALL ACCUMULATIONS OF 6 TO 12 INCHES WITH ISOLATED AMOUNTS OF 20
INCHES ARE POSSIBLE OVER THE DOMINICAN REPUBLIC AND HAITI. THESE
RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

Track projection as of early this afternoon for Emily.

Always subject to change, but the forecast strength remains below hurricane force of 75 mph winds until early next week.

Enjoy the seasonal temperatures the next couple of days. Overnight temperatures may allow you to shut down the A/C and bring in some outside air.

CE

Severe Thunderstorm Watch this morning

Posted at 6:28 AM on August 2, 2011 by Craig Edwards (5 Comments)
Filed under: Thunderstorms, dew point

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

CENTRAL AND SOUTHERN MINNESOTA
WESTERN WISCONSIN

EFFECTIVE THIS TUESDAY MORNING AND AFTERNOON UNTIL 100 PM CDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES NORTHEAST
OF EAU CLAIRE WISCONSIN TO 10 MILES SOUTH OF ORTONVILLE
MINNESOTA.

Heavy rain fell across portions of northeast Minnesota and northwest Wisconsin overnight. Three and a third inches of rain was reported at Askov in Pine County, MN and near Floodwood in St. Louis County, MN. The automated gauge at the Duluth Airport captured two and a half inches of rain.

Severe thunderstorms are possible in the southern portion of Minnesota and west central Wisconsin this morning as a cool front slips through the region. Less humid conditions are on tap for Wednesday.

Here's the complete report of the record dew point for this summer as published Monday afternoon by the Minnesota State Climate Office:

The Exceptionally Muggy Summer of 2011

The National Weather Service is forecasting a break in the high dew point temperatures over the next few days after the muggy day today. So far this summer as of 3pm August 1, there have been 274 hours of dew point temperatures of 70 degrees or higher recorded at the Twin Cities International Airport. The record is 512 hours in 2002. What really stands out are the counts of extremely muggy dew point temperatures. So far this summer as of 3pm August 1, there have been 98 hours of dew point temperatures of 75 degrees or higher. This breaks the old record of 78 hours that was set back on 2001.

Twin Cities International Airport
Greatest Number of hours with dew point
temperature of 70 degrees F
(1945-2011)

Rank Year Hours
----------------------
1. 2002 512
2. 1983 392
3. 1995 387
4. 2001 357
5. 1955 345

1981-2010 average = 182

so far in 2011 274
(through 3pm August 1)

Twin Cities International Airport
Greatest Number of hours with dew point
temperature of 75 degrees F
(1945-2011)

Rank Year Hours
--------------------
1. 2011 98 (as of 3pm August 1)
2. 2001 78
3. 1999 64
4. 1987 60
5. 1995 56

1981-2010 average = 18

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Increasing threat of dangerous storms

Posted at 3:55 PM on August 1, 2011 by Craig Edwards (3 Comments)
Filed under: Climate, Rainfall, Target Field, Thunderstorms, Tornadoes, dew point

This visible satellite image shows a couple of important aspects about this afternoon's weather. First, the clouds that remained over eastern Minnesota and western Wisconsin which kept temperatures from climbing into the lower 90s. Second, the clearing in western Minnesota that has allowed sunshine and high dew points to produce heat index values about 100; including 106 at 3PM in Canby.

In the previous blog you'll note the Storm Prediction Center's rather high probability of tornado potential in western Minnesota. There is a boundary from the differential heating due to the cloud-free area and the persistent cloud cover. This is displayed nicely in the graphic of the dew points, temperatures and pressure field as generated from 3PM surface observations.

Temperature contours are in red, dew point highlighted by colored background and pressure field in black. Basic meteorology suggests the inflow of winds from the south and southeast, along with the advancing low pressure, high dew points and afternoon heating will result in thunderstorm development in eastern South Dakota and western Minnesota.

We'll watch how this unfolds in the later afternoon and early evening hours.

Meanwhile, Pete Boulay of the State Climate Office shared this tid-bit after probing the dew points recorded this summer at the Twin Cities International Airport. So far this summer as of 3pm August 1, there have been 98 hours of dew point temperatures of 75 degrees or higher. This breaks the old record of 78 hours that was set back on 2001.

Some branches were blown down along with power lines as the storms swept through east central Minnesota between 1230PM and 230PM this afternoon. Here's a link to the storm reports out of the Chanhassen NWS Office.

Heavy rain also was reported with over two inches at Hutchison and an inch and a half at Target Field near downtown Minneapolis from late morning to mid afternoon.

Stay abreast of potentially dangerous weather conditions developing as we go into the evening hours.
CE

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Uncharted Heat Index values

Posted at 7:53 AM on July 18, 2011 by Craig Edwards (11 Comments)
Filed under: Climate, Crops, Heat, Microclimates, dew point

Austin Schoen (left), Mark Schauer (center) and Tanner Schauer cool off on the Bumper Boats ride at Lilli Putt in Coon Rapids, Minn., on July 18, 2011. (MPR Photo/Nikki Tundel)

While we are calling this sweltering, oppressive atmosphere a Heat Wave, it equally worthy of being called a High Dew Point Warning. Yesterday afternoon and evening dew points, a very good indicator of the moisture in the atmosphere, were in the lower 80s over a large swath of southern Minnesota. It is very rare to observe sustained high dew points over a broad area this far north.

Dew point measurement can me impacted by the microclimate of the sensors location. We see dew points at their highest in southern Minnesota from mid July through about mid August. A number of us in the weather business believe that these seasonally high dew points are the results of the evapo-transpiration of the maturing corn corps across Iowa and southern Minnesota. Moisture is released back into the low levels of the atmosphere and we feel its affects.

A slight drop in dew points is seen for today. We may well see a few degrees of additional heat on the thermometer. That translates to Heat Index values of 105 to 115, in the shade, during the middle of the day. This is excessively sweltering when you add into the equation direct sunlight. Stay out of the sun today if you can. Unless you are standing in the lake.

Dogs and cats instinctly slow down in this weather. If your dog needs to have a walk, make it a quick trip early in the morning or in the evening. Provide plenty of water for pet during this sultry period.

Follow the advice from health officials with regard to your well being. Apply the number one rule; slow down. Dress in light colors with a brimmed hat.

Heat spell breaks a bit towards the end of the week. Just so you know; the climate records document the next seven to ten days as the warmest period during the calendar year.

The sensible temperature is about fifteen degrees warmer in the direct sunshine.

Think cool thoughts today.
CE

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Measuring atmospheric moisture at the surface

Posted at 4:03 PM on July 7, 2011 by Craig Edwards (2 Comments)
Filed under: dew point

When you listen to a weather observation it sounds so simple. There are a number of automated meteorological observation units that take nearly continous weather observations. The official NWS automated observations are recorded and transmitted by ASOS-Automated Surface Observation System.

The FAA has augmented these observations with their own units known as AWOS-Automated Weather Observation Systems. Here is a link to the automated observation sites. In addition, the Minnesota Department of Transporation has some weather observing sites.

When I began my career with the NWS at Mitchell Field in Milwaukee I was a weather observer. Fortunately we had automated sensors already in the early 1970s. We were required to observe the cloud cover, along with the horizontal visibility on an hourly basis. This visual observation along with the temperature, dew point, wind and pressure was transmitted by teletype.

On a regular basis we would ensure the automated temperature and dew point sensor was reading accurately. Once a week the weather observer would stand in a shaded grassy area and swing a sling psychrometer that would measure the dry bulb and the web bulb temperatures. We would then calculate the dew point; ultimately deriving the relative humidity.

Here's a photo of how they still determine relative humidity when on a forest fire incident.

Though not clearly viewed, there is a sling psychrometer in his right hand.

If you want to read more about the meteorological measurements you can check your knowledge at this NWS website.

I was partial correct when I said you would notice an increase in dew points today. The Twin Cities International Airport had a dew point of 51 degrees at this time on Wednesday. The dew point rose to 65 degrees when light rain fell at 6AM, but has since fallen back to 56 degrees. The dew point is in the lower 60s at Rochester this afternoon.

Check out the change in cloud cover from early this morning (see previous blog) to this afternoon on the visible satellite image.

Thunderstorms were firing up in portions of the Minnesota River Valley in west central Minnesota.

Latest computer model information still supports the best chance for thundershowers in central Minnesota on Saturday afternoon and evening.

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Dazzling Mt. Etna video; Lightning vs. plane at Heathrow

Posted at 5:42 PM on May 12, 2011 by Paul Huttner
Filed under: Volcanoes, dew point

Italy's Mt. Etna is Europe's most active volcano and erupts frequently, but it doesn't get much better than this for video. Check out the dazzling images as Mt. Etna erupts again in Sicily.

The story from UPI:

"CATANIA, Italy, May 12 (UPI) -- Mount Etna on the Italian island of Sicily sent smoke, volcanic shards and ash thousands of feet into the air Thursday.

"Sunday's stage is not at risk. The stretch in question is only the last 4 miles on Etna," director Angelo Zomegnan said. "But on-site teams are already working to clear the road. We are calm."

Lightning vs. plane in London:

I buried this near the end of this mornings post, but it's probably worth another look.

Check out this amazing video of lightning hitting a plane last month at London's Heathrow Airport.

Fishing opener weather history all over the map:

My detailed forecast for the fishing opener 2011 is here.

The Minnesota Climatology Working Group has a great recap of historical weather conditions for the Minnesota fishing opener. As you might guess, the weather can be all over the place in mid-May.

2011 Minnesota Fishing Opener Weather

Minnesota's Fishing Opener weather is typified by partly cloudy to cloudy skies, morning temperatures in the low 40's, and afternoon temperatures climbing to near 70. Three out of four years are free of measurable precipitation. A trace of snow has been reported in northern Minnesota on at least five of the last 63 fishing openers. On at least four occasions, some lakes were still frozen for the opener. Generally there is enough wind to be felt on the face, maybe enough to 'fly' a flag. Weather on Minnesota fishing opener dates is highly variable. 63 years of fishing opener weather data are summarized here to offer a glimpse of what is 'typical' and what is 'extreme'.

Good Luck!

Dew point records smashed Tuesday:

UM Climate Guru and my MPR colleague Mark Seeley has some great info on how Tuesday's July like air mass featured tropical humidity levels that smashed dew point record for May 10th.

Topic: High Dewpoint Records for May

"Tuesday, May 10th was quite a day in Minnesota. During the afternoon strong southeast winds brought in very warm, moist air across southern counties. Many observers reported near-record setting or record setting temperatures in the 90s F, spiking between 4:00 and 6:00 pm. Some of the record-setters included:

The dramatic rise in temperature and dewpoint helped fuel severe weather across the state. There were over 40 reports of large hail during the evening of May 10th including 2.0 inch diameter hail stones at Chanhassen, Eden Prairie, Forest Lake, and Brainerd. Golden Valley, St Louis Park, and Fort Ripley reported 2.5 inch diameter hail, and Albertville reported 2.75 inch diameter hail."

As always, you can hear Mark's commentary exclusively on MPR's Morning Edition with Cathy Wurzer at abour 6:45 Friday morning.

PH

Freezing rain chances greatly diminished

Posted at 9:09 PM on December 29, 2010 by Craig Edwards
Filed under: dew point

Milder air has pentetrated Minnesota this evening. Not only have temperatures climbed into the middle thirties over the southern half of the state, but dew points have increased as well. This will result in the potential for dense fog.

As a trough of low pressure sets up over far western Minnesota overnight and Thursday a large portion of the state will stay on the mild side of this system. A light rain is likely for southeast Minnesota.

Accumulating snowfall is still in the forecast for far northwest Minnesota into Thursday afternoon. A band of mixed rain and snow is possible from about Granite Falls to Hibbing.

The second system on Friday remains a work in progress. A band of heavy snow is likely to set up in west central Minnesota and expand east and northeast during the afternoon and evening.

An icy blast of arctic air is in the offing to begin the New Year.

From HRRR model valid at 8AM CST. Note temperatures well into the 30s for all but far northwest Minnesota. Winds are indicated in knots.
CE

Corn adding humidity to Minnesota

Posted at 4:45 PM on August 17, 2010 by Paul Huttner (6 Comments)
Filed under: dew point

Update 4:45pm: (Original post 8:29am)

Check out the 4pm dew point reading of 68 degrees at St. James Tuesday.

Notice how the 68 degree dew point reading is a good 10 degrees higher than many of the surrounding surface sites. It looks like the corn is doing a good job of evaporating soil moisture into the lower atmosphere in corn country today!

PH

Anyone who's driven through southern Minnesota knows corn is king in the summer landscape. Now we know it's making our summers a bit more humid too.

According to Pete Boulay at the Minnesota State Climatology Office, Minnesota's corn crops may be boosting dew points by as much as 1 to 5 degrees on summer days in and near cornfields.

Pete confirmed the readings last week by taking measurements with a little thing called a "pshychro-dyne" instrument which measures temperatures used to calculate the dew point. August 12th was a hot steamy day (high was 92 at MSP) with relatively light winds in the morning. So Pete headed out into the dense corn stand at the UM St. Paul Campus and began to take readings.

Here's what he found: (These are excerpts from Pete's email)

Hello all,

State Climatology Office
DNR - Division of Ecological and Water Resources

The salient point here is that Pete found dew points between 1 and 5 degrees F higher in the corn on a hot summer day, than in nearby areas. Now, this is by no means a comprehensive scientific study, it's just one really qualified climate expert taking readings in a corn field. But I'll take Pete Boulay and his "psychro dyne" readings any day.

A little inside baseball here. Several of us in the local meteorological community have wondered if automated weather stations like St. James read higher dew points because they are located very near cornfields. Corn is an efficient evaporator of soil moisture, and releases that moisture into the surrounding air.

My take away from Pete's little experiment is that corn does play a role by increasing summer dewpoints in densely planted areas. The effect is real, and millions of acres in the Midwest are planted with corn. This is not instrument failure, but rather success in picking up on the air mass modification by some row crops.

The next question is; are the higher moisture levels significant enough to cause additional low level moisture to fuel thunderstorms and enhance rainfall? In science, we call this process a "feedback loop."

There are still many unanswered questions about corn and humidity. But on one day in August in the sweaty summer of 2010, a guy with a "psychro dyne" in a corn filed in St. Paul confirmed what many meteorologists have long observed. The corn is making things more humid in Minnesota....at least in the middle of the corn field.

Also unanswered is whether or not Pete saw Shoeless Joe Jackson dissapear into the corn at the UM St. Paul Campus. (Sorry, I couldn't resist.)

PH

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