Hot or cold: Denver's problematic weather records. (Denver Weather Examiner)
Does a move of 12 miles make a difference in what type of weather is seen in Colorado? Longtime residents know that our weather can vary greatly over short distances and this has many questioning the placement of Denver’s official weather monitoring station.
From 1871 to 1949 Denver’s weather was recorded at the National Weather Service’s office in downtown Denver. In January 1950 a move was made to Stapleton International Airport.
As that facility aged Denver opened Denver International Airport on the plains northeast of Denver in 1995. The weather service followed suit and moved the Mile High City’s official weather station the 12 miles to DIA.
Since that time, many weather watchers have noticed problems – DIA is consistently warmer and drier than the old site at Stapleton. Further, its remote location gives conditions far from where most people in Denver live and thus doesn’t accurately represent what they are experiencing.
Even bigger issues arise when comparing weather data taken today with measurements previously recorded at Stapleton or downtown. The different microclimates of the sites are so different that it becomes much like comparing apples and oranges.
This was recently made evident with the string of 90 degree or warmer days we put together. If you went by the station at DIA, the streak lasted 18 days putting in a three way tie for the second longest streak in Denver history. However, no monitoring station closer to the city was as warm.
Further, while July was certainly a wet month, DIA’s precipitation measurements fell far short of most other locations.
Amid concerns about a warming climate, can we trust the measurements at DIA? How is it possible to compare the weather today with historical weather when there is such a large discrepancy?
We recently tackled this topic on the Denver Weather Examiner and the conclusion is obvious – It simply is impossible to correlate current weather records with Denver’s historical ones. Further, the National Weather Service seems intent on ignoring the issue.
July 31 to August 6 - This Week in Denver Weather History
How does 42 degrees sound right about now? That mark is one of the highlights of this week in Denver weather history. It was the low temperature recorded twice in our past and the coldest July temperature on record. Many more notable events have also occurred.
13-5
In 2008…a streak of 24 consecutive days of 90 degrees shattered the previous record of 18 consecutive days established in 1901 and 1874. Ironically…no new single day record high temperatures were set in the month of July. In August however…a record of 104 degrees was set on the 1st…and another record of 103 degrees was set on the 2nd. In addition…a record low min of 70 degrees was set on August 2nd.
18-2
In 1987…a streak of 16 consecutive days of 90 degrees ranked 4th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
27-31
In 1956…96 percent of the total precipitation for the month of July occurred over the last five days of the month. Heavy thunderstorms produced 4.00 inches of rainfall at Stapleton Airport. This amount of precipitation in 5 days or less had been exceeded only 3 times in previous record. The last time had been in December of 1913 as snow. Considerable property damage occurred across metro Denver from flooding.
31
In 1873…the all-time lowest recorded temperature in July… 42 degrees…occurred. The same temperature also occurred on July 4…1903.
In 1874…during the late afternoon rain and hail fell for 5 minutes followed by brief heavy rain. Pieces of solid ice of irregular shape fell upon the roof of the station. The hail stones measured 1 1/2 inches in diameter. Precipitation (rain and melted hail) was only 0.16 inch.
In 1889…the high temperature climbed to 100 degrees in downtown Denver.
In 1919…heavy thunderstorm rainfall totaled 2.59 inches in downtown Denver during the evening. Rainfall was 1.90 inches in an hour…a new record at that time.
In 1961…over an inch of rain in a short period of time caused flooding of streets and basements in Denver. Rainfall totaled 1.30 inches at 11th and Lincoln in central Denver.
In 1964…the temperature reached 91 degrees in Denver…making this the 27th day of the month that the temperature reached 90 degrees or more. This is the all time record for 90 degree days in a month in Denver.
In 1972…one inch diameter hail fell in Hudson northeast of Denver.
In 1976…during the evening hours extremely heavy thunderstorm rains produced flash flooding in Big Thompson Canyon which killed 144 people between Estes Park and Loveland. No significant weather occurred in metro Denver at the time.
In 1987…1 inch diameter hail fell in Lakewood and 3/4 inch hail fell near Louisville. Southeast Boulder County was drenched with 1.25 inches of rain in just 20 minutes.
In 1993…thunderstorm winds damaged a chimney of a home near Parker.
In 1996…a weak tornado (f0) was sighted 12 miles east of Denver International Airport. No damage was reported.
In 1998…heavy monsoonal thunderstorm rain triggered a mud slide in Blackhawk. The mudslide blocked Main St. and caused an estimated half million dollars in damage to a casino. Heavy thunderstorm rain…up to 3 inches in an hour…caused a flash flood along Buffalo Creek. Portions of County Road 126 just south of the town of Buffalo Creek were washed out. The flood waters nearly washed away the bridge as mud and debris slammed into the structure. Hail to 1 3/4 inches in diameter fell near Idaho Springs.
In 2004…severe thunderstorm winds toppled a 65-foot blue spruce tree in Parker. The tree landed on a home damaging the roof and gutters. The downed tree poked dozens of holes into the shingles.
When the Space Shuttle Atlantis came to a slow stop on the runway at Kennedy Space Center on July 21, it was the end of an era of spaceflight. Astronauts aboard the International Space Station captured amazing imagery of Atlantis’ last descent through the atmosphere.
It was a sad day for many Americans when the space shuttle era came to a close with the last shuttle mission. Shifting priorities, lack of direction and leadership and politics have all wreaked havoc with the United States’ space program.
As Atlantis is prepared for retirement as a museum piece along with her sister ships, NASA is left without a way of its own to put a human in space. Meanwhile, cash-strapped Russia manages to forge ahead with its Soyuz program and an emerging space power in China threatens our nation’s leadership in space.
Astronauts aboard the International Space Station captured this image of Space Shuttle Atlantis as it returned to the Earth on July 21, 2011. (NASA)
From NASA:
Like a comet streaking across the atmosphere, the Space ShuttleAtlantis left space for the final time on July 21, 2011, descending to a smooth landing at NASA’s Kennedy Space Center in Florida. This astronaut photograph, taken from the vantage of the International Space Station (ISS), shows the streak of an ionized plasma plume created by the shuttle’s descent through the atmosphere.
At the time of the image, the ISS was positioned northwest of the Galapagos Islands, while Atlantis was roughly 2,200 kilometers (1,367 miles) to the northeast, off the east coast of the Yucatan Peninsula. The maximum angle of the shuttle’s descent was roughly 20 degrees, though it appears much steeper in the photo because of the oblique viewing angle from ISS. Parts of the space station are visible in the upper right corner of the image.
In the background of the image, airglow hovers over the limb of the Earth. Airglow occurs as atoms and molecules high in the atmosphere (above 80 kilometers, or 50 miles altitude) release energy at night after being excited by sunlight (particularly ultraviolet) during the day. Much of the green glow can be attributed to oxygen molecules.
July 24 to July 30 - This Week in Denver Weather History
As we near the end of July the weather in Denver tends to be a bit more stable. That doesn’t mean the severe weather threat disappears as can be seen at our look back at this week in Denver weather history. Particularly notable are lightning injuries and deaths, flash flood events and even tornadoes.
7-25
In 1934…a streak of 15 consecutive days of 90 degrees ranked 5th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
13-5
In 2008…a streak of 24 consecutive days of 90 degrees shattered the previous record of 18 consecutive days established in 1901 and 1874. Ironically…no new single day record high temperatures were set in the month of July. In August however…a record of 104 degrees was set on the 1st…and another record of 103 degrees was set on the 2nd. In addition…a record low min of 70 degrees was set on August 2nd.
18-2
In 1987…a streak of 16 consecutive days of 90 degrees ranked 4th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
20-25
In 1965…heavy showers and thunderstorms doused metro Denver with significant rain each day. Rainfall for the six days totaled 5.16 inches at Stapleton International Airport. Massive rainfall occurred on the 20th…21st…and 25th… Flooding streets and basements and causing streams to overflow. The heaviest rainfall…2.05 inches…at Stapleton International Airport occurred on the 25th.
24
In 1896…heavy cloudbursts in the foothills west of Denver caused flash flooding on Bear Creek…Clear Creek…Golden Gate Gulch…and Mount Vernon Creek…resulting in a total of 27 deaths. The downpour dislodged large Boulders…one of which crushed a house. The heavy rain also caused a dam on cub creek to wash out…adding even more water to the flood. A wall of water as high as 10 feet flooded Evergreen and passed down bear creek…washing away many structures along the way. The flood crest produced 3 feet of water in downtown Morrison during the early evening. Flash flooding on Mount Vernon Creek added to the flooding in Morrison. In Golden…the flooding washed out bridges on clear creek and on Cresman and Tucker gulches and forced the closure of the power plant. In Denver…a thunderstorm produced hail of unknown size during the afternoon and rainfall of 1.23 inches overnight.
In 1958…a thunderstorm wind gust to 52 mph was recorded at Stapleton Airport.
In 1965…heavy rain caused flooding on clear creek and tucker gulch in Golden and west Denver. Damage in Golden was estimated at 80 thousand dollars. Heavy rain south of Denver washed out temporary earthen bridges constructed following the June floods in Castle Rock…Littleton… Englewood…and Denver. Bear creek in south Denver reached flood stage. A cloudburst on cub creek in Evergreen washed out bridges and roads. Heavy rain fell over all the Denver and Aurora areas…causing some flooding of roads…streets… And bridges. A man drowned in a flooded irrigation canal near Hudson. Heavy rain caused flooding of streets and roads in Blackhawk and central city. Hail caused minor damage in Idaho Springs.
In 1967…seven bridges were washed out along a normally dry creek bed south of State Highway 7 west of Brighton. One car was washed into the creek when a bridge gave way.
In 1970…hail stones to 1 1/4 inches in diameter fell in the foothills of Jefferson County southwest of Denver.
In 1971…golf ball size hail was reported in foothill areas of Jefferson County west of Denver. A funnel cloud was sighted in Aurora. Wind gusts estimated at 60 mph…hail… And heavy rain up to an inch in 15 minutes caused local flooding and some other damage in several areas of metro Denver. Hailstones to 3/4 inch in diameter fell 7 miles southeast of Denver.
In 1973…a thunderstorm wind gust to 52 mph was recorded at Stapleton International Airport where one inch diameter hail was measured.
In 1981…strong winds downed a power line in northeast Denver. Wind gusts to 50 mph were recorded at Chatfield Reservoir.
In 1987…3/4 inch diameter hail fell 5 miles northeast of Commerce City.
In 1996…hail…up to 1 3/4 inches in diameter…fell at Chatfield Reservoir. Hail to 3/4 inch in diameter was measured near Bennett.
In 2000…lightning struck near two golfers at ute creek golf course near Longmont…knocking them to the ground. The men received only minor injuries.
In 2001…lightning from a thunderstorm knocked out electrical power to about 1500 residents in the city of Denver.
In 2004…a chilly day with fog and thunderstorms resulted in two temperature records. The low temperature of 49 degrees was a record minimum for the date. The high temperature of only 58 degrees was a record low maximum for the date.
July 17 to July 23 - This Week in Denver Weather History
Our weekly look back at Denver weather history always has interesting items but this week one stands out in particular. Denver has never officially recorded snow during the month of July. However, before official records began in 1882, the U.S. Army Signal Service weather observer reported snow on July 17, 1872!
7-25
In 1934…a streak of 15 consecutive days of 90 degrees ranked 5th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
13-5
In 2008…a streak of 24 consecutive days of 90 degrees shattered the previous record of 18 consecutive days established in 1901 and 1874. Ironically…no new single day record high temperatures were set in the month of July. In August however…a record of 104 degrees was set on the 1st…and another record of 103 degrees was set on the 2nd. In addition…a record low min of 70 degrees was set on August 2nd.
16-18
In 1997…an extended hot spell resulted in 3 temperature records being set. The maximum temperature reached 98 degrees on each of the days…setting records on the 16th and 18th. The low temperature of 71 degrees on the 17th was a record high minimum for the date. The high temperature reached 100 degrees on the 17th at the site of the former Stapleton International Airport.
17
In 1872…the U.S. Army Signal Service weather observer recorded snowfall during the early morning hours in the hand written daily weather journal: “rain commenced at 1:30 a.m. changing about 3 a.m. to snow & in about half an hour to rain again; it continued until 6 a.m.” this is the only recorded occurrence of snowfall in Denver in July…but this report is not included in the “official” station snowfall records…which did not begin in Denver until January 1…1882. The low temperature on this morning was 45 degrees…which is sufficiently cold for the occurrence of light stratiform snowfall.
In 1918…a thunderstorm produced hail to an inch in depth on the ground. The stones varied in size from a small cherry stone to nearly 1/2 inch in diameter. Not much permanent damage was done to crops. Precipitation totaled 0.40 inch…and northeast winds were sustained to 25 mph with gusts to 28 mph.
In 1971…the temperature reached a high of 101 degrees at Stapleton International Airport.
In 1983…3/4 inch diameter hail fell at Lafayette…while golf ball size hail pelted Brighton and Northglenn where funnel clouds were also sighted.
In 1986…1 1/2 inches of rain fell in an hour and 15 minutes in southeastern Aurora. Thunderstorm rainfall totaled 0.89 inches at Stapleton International Airport.
In 1987…a small tornado was sighted near Watkins…in the vicinity of Front Range airport.
In 1997…lightning ignited an oil well tank holding 10 thousand gallons of oil…16 miles northwest of Bennett. About 200 acres of grassland burned before the fire could be extinguished. A dry microburst produced a wind gust to 52 mph at Denver International Airport.
In 2000…an estimated 2 inches of rain fell in less than an hour…causing two secondary roads in buck and miller gulches in the hi meadows fire burn area to wash out. Water also covered Jefferson County road 68 which connects to Bailey. Homeowners in pine valley estates attempted to divert some of the runoff by piling stacks of hay on the hillside above their homes. Torrential rainfall…up to 3.50 inches an hour…caused flash flooding along Whiskey Gulch near Elizabeth. Several roads were washed out and basements flooded during the storm. Along County Road 13… About 6 miles north-northwest of Elizabeth…rushing water washed away a 15-foot section of the road. The floodwaters forced debris and mud into four huge culverts…sending water over the road. At Denver International Airport…an United Airlines ground crew worker was struck by lightning as she was loading a Boeing 747 jumbo jet. The woman was injured when lightning either hit the jet or the loading equipment that she was working near. The 25-year-old woman received only minor injuries.
In 2006…outflow from severe thunderstorms to the southeast of metro Denver produced southeast sustained winds to 35 mph with gusts as high as 52 mph at Denver International Airport during the late evening.
18
In 1874…the temperature climbed to 90 degrees or more for the 18th consecutive day…setting a record. The record was equaled from July 6th through the 23rd in 1901.
In 1902…a thunderstorm produced northwest winds sustained to 45 mph with gusts to 48 mph along with rain and hail. Total precipitation was 0.53 inch.
In 1911…a shower produced north winds sustained to 44 mph.
In 1958…1 1/2 inch diameter hail fell 9 miles west-southwest of Stapleton Airport.
In 1981…a thunderstorm bombed Evergreen with about 2 inches of rain in 45 minutes. A heavy hailstorm left 5 to 7 inches of hail on the ground in some places and stopped the Colorado Open golf tournament at Hiwan.
In 1985…over 2 inches of rain doused the southwest suburbs of Denver. Street flooding occurred in the Montbello area of northeast Denver.
In 1992…nickel size hail fell across central Douglas County near Castle Rock and Sedalia. One inch diameter hail fell in Castle Rock.
In 1993…thunderstorm winds gusted to 60 mph at Strasburg east of Denver.
In 2004…heavy thunderstorm rainfall caused flooding over parts of the Virginia Canyon Road near Idaho Springs. Several sections of the roadway were washed out. The road was closed temporarily for repairs.
Denver easily broke the 24 hour precipitation record for July 13th.
It is readily apparent that July has thus far been a wet month given that we have seen eight straight days of thunderstorms. Yesterday the storms set a record for precipitation and Denver is on pace to make the month one of the wettest Julys on record.
Out at Denver International Airport yesterday, 1.03” of precipitation was recorded. This set the record for the date easily besting the old record of 0.45” set in 1993.
Here in Thornton we recorded 0.45” yesterday so a good bit less than out at the airport but still a decent shot of precipitation.
This brings Denver’s official total to 3.19” for the month so far. Average for the entire month of July is 2.16” so we are far ahead of that.
Number 10 on the ‘top 10 wettest Julys’ occurred in 1985 with 3.71”. Given the fact that the forecast continues to contain daily thunderstorms for the foreseeable future, there is a good chance we will exceed that before the month is over.
Thornton is ahead of the game in comparison to DIA as we have recorded 4.52” so far this month.
Lightning strikes east of 120th Avenue and Fairfax during Tuesday night's storms. View more images in the slideshow below. (ThorntonWeather.com)
For eight days in a row monsoonal flow fed thunderstorms have struck Thornton and Tuesday night brought arguably the best show yet. Heavy rain, hail, gusty winds and an extraordinary amount of lightning roused residents soon after nightfall.
Storms initially formed in the afternoon and were focused south of Denver in Elbert County. Near Kiowa, Elizabeth and Agate hail up to 1 3/4” in diameter was recorded. The slow-moving storms deposited as much as five inches of rain near Agate. Three twisters were reported in Elbert County but no damage was realized.
It appeared for a time that Thornton was going to escape the intense weather but once the sun went down the picture changed dramatically. Seemingly out of nowhere a storm cell popped up at around 9:20pm and moved across the north Denver metro area.
Heavy rain fell across a large part of the area from downtown northward to Thornton. 1.76 inches of rain was recorded north of downtown Denver at DenverWX.com as the storm passed through.
Street flooding was reported across the surrounding areas causing difficulty for motorists.
Here in Thornton we were pounded with heavy rain and a great deal of pea-sized hail. ThorntonWeather.com recorded its first inch of rain in only 14 minutes and the storm total for the overnight storm was 1.90 inches.
Strong winds also brought down trees and power lines knocking out power to nearly 10,000 Denver area residents including some in Thornton. Xcel Energy reports power has been restored to most areas this morning.
Denver International Airport recorded a thunderstorm wind gust of 66mph shortly before 10:00pm. A ground stop was issued and all flights were temporarily delayed while the storm moved through.
Forecasters had predicted a late and shorter than normal monsoon season due to La Niña’s lasting effect – that however has not proven to be true.
A common scene this past week - thunderstorms develop over the Denver area. Watch video of the recent street flooding in Thornton below. (Twitpic / CodyCrouch)
La Niña is winding down and normally we would expect a drier than normal monsoon. Mother Nature however has other plans as she not only brought the season to Thornton early, it came with a vengeance this week.
In a presentation that just came out at the first of the month, the National Weather Service discussed the coming monsoon. At that time forecasters predicted a drier and shorter than normal monsoon for the Colorado Front Range. Thus far it has been anything but.
This past week copious amounts of moisture have streamed into Colorado. Coupled with daytime heating leading to a good deal of atmospheric instability, thunderstorms have been a daily occurrence. Strong winds and heavy rain have occurred virtually daily.
Over the past five days Denver has recorded 1.78 inches of rain at the city’s official monitoring station at Denver International Airport. Closer to where population actually lives even greater amounts have been seen.
On Friday evening, a slow-moving thunderstorm dumped heavy rain on the southern parts of Thornton. Video footage from storm chaser Tony Laubach (below) shows the end result as streets in the area of I-25 and 84th Avenue were flooded.
Is there an end in sight? Not in the immediate future. For at least the next few days atmospheric moisture will continue to be in abundance and we will continue to see the same general pattern. By mid-week we may see some drying but we can’t entirely eliminate the threat of afternoon thunderstorms.
July 10 to July 16 - This Week in Denver Weather History
Our look back at this week in Denver weather history demonstrates why July is considered the Mile High City’s stormiest month. Many instances of flooding rains, damaging wind and hail and dangerous lightning are seen in our past.
From the National Weather Service:
1-18
In 1874…a streak of 18 consecutive days of 90 degrees tied for second with another streak that was later set in the summer of 1901. The record of 24 consecutive days was established in the summer of 2008.
6-23
In 1901…a streak of 18 consecutive days of 90 degrees tied for second with another streak set in the summer of 1874. The record of 24 consecutive days was established in the summer of 2008.
7-25
In 1934…a streak of 15 consecutive days of 90 degrees ranked 5th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
9-10
In 1980…a series of severe thunderstorms hit metro Denver… Dumping heavy rain and producing a spectacular lightning display lasting for several hours. A number of homes were damaged by lightning. Winds gusted to 60 mph at Stapleton International Airport where about half an inch of rain fell in just 10 minutes along with 1/4 inch diameter hail. The evening thunderstorms continued into the early morning hours with total rainfall of 1.35 inches at Stapleton International Airport.
In 1998…thunderstorm rainfall totaled 2.04 inches at the site of the former Stapleton International Airport.
10
In 1878…a lunar rainbow was observed during a light mist and fog.
In 1895…the temperature warmed to a high of only 53 degrees… The all-time record lowest maximum temperature for the month of July.
In 1967…golf ball size hail damaged aircraft at Jefferson County Airport near Broomfield.
In 1983…two people were injured when struck by lightning just southwest of Morrison. A man was injured when he was swept downstream by a flash flood on a tributary of clear creek in the canyon 8 miles west of Golden. Heavy thunderstorm rains caused mudslides which closed several roads. Rainfall amounts included: 1.75 inches in 20 minutes in southeast Denver…1.26 inches in 35 minutes in Boulder…2.14 inches in 2 hours in Lakewood…1.70 inches in 45 minutes in Aurora…and 1.25 inches in 30 minutes atop Floyd Hill in the foothills west of Denver.
In 1992…storm spotters reported 3/4 inch diameter hail near the construction site of the new Denver airport just northeast of the city.
In 1995…microburst winds toppled a pine tree 60 feet high and 2 feet in diameter in Denver. The tree fell and injured a man nearby. Microburst winds to 59 mph broke the glass on a door at the national weather service forecast office at the site of the former Stapleton International Airport.
In 1998…thunderstorm rainfall totaled 2.35 inches at Denver International Airport.
In 2000…three children were injured…one critically…when lightning hit a nearby tree at panorama point atop Flagstaff Mountain just west of Boulder. Lightning hit the tree…entered the ground…then struck the children. Lightning sparked a grassfire that burned about 50 acres at the Rocky Flats Environmental Test Facility. Also… Lightning sparked at least 6 fires in the Hudson and Keenesburg areas as thunderstorms…accompanied with heavy rain…large hail…and tornadoes…moved through southern Weld County. Over 2 inches of very heavy rain caused flooding along an I-76 exit ramp near Keenesburg. The fire department rescued 15 stranded motorists as high water inundated sections of the exit ramp and adjacent highway. Basements were also flooded in Keenesburg. One home reportedly had 7 feet of standing water in the basement before the rain subsided. A weak tornado (F0) touched down briefly near Brighton…but caused no damage.
In 2001…a severe thunderstorm dumped 7/8 inch diameter hail in wheat ridge.
In 2002…severe thunderstorms pelted the southern suburbs of metro Denver with large hail. Hail as large as 3 inches in diameter fell 6 miles southeast of Parker. Other large hail reports included 2 inch diameter hail around centennial airport and 3/4 inch hail near Sedalia and Deckers. Hail as large as 3/4 inch was also reported in Broomfield. Runoff from heavy thunderstorm rainfall in the Hayman fire burn area flooded lost creek ranch with up to 18 inches of water just off State Highway 126. Floodwaters damaged a very expensive rug in the lodge. A driveway to a residence was washed away. In Douglas County…runoff damaged forest access roads in the Turkey Creek drainage.
Two of the most famous signers of the Declaration of Independence could also be considered weathermen.
Certainly anyone who has studied the Founding Fathers is well aware of Benjamin Franklin’s electrifying kite-flying experience. What many Americans may not know is that he was one of the first storm chasers and his fellow signer of the Declaration of Independence, Thomas Jefferson, was a weatherman in his own right.
Benjamin Franklin’s interest in the weather spanned virtually his entire lifetime. He was intrigued by the weather and deduced the movement of storms going on to accurately theorize about low and high pressure as the basis for weather patterns.
His Poor Richard’s Almanac featured some of the nation’s first weather forecasts, penned by Franklin under the pseudonym of Richard Saunders. Later in life he would record weather observations during his numerous Atlantic crossings and six years before his passing he published a number of “Meteorological Imaginations and Conjectures.”
Franklin also was one of the nation’s first storm chasers. In a letter to Peter Collinson dated August 25, 1755 Franklin relayed his experience chasing what he called a whirlwind in Maryland the prior April.
He wrote, “We saw, in the vale below us, a small whirlwind beginning in the road and showing itself by the dust it raised and contained. It appeared in the form of a sugar-loaf, spinning on its point, moving up the hill towards us, and enlarging as it came forward. When it passed by us, its smaller part near the ground appeared no bigger than a common barrel; but widening upwards, it seemed, at forty or fifty feet high to be twenty or thirty feet in diameter. The rest of the company stood looking after it; but my curiosity being stronger, I followed it, riding close by its side, and observed its licking up in its progress all the dust that was under its smaller part.”
America’s first statesman goes on to detail how he followed the meteorological phenomena saying, “I accompanied it about three-quarters of a mile, till some limbs of dead trees, broken off by the whirl, flying about and falling near me made me more apprehensive of danger; and then I stopped, looking at the top of it as it went on, which was visible, by means of the leaves contained in it, for a very great height above the trees.”
Certainly it would appear Franklin encountered a strong dust devil or possibly even a weak tornado.
On July 4, 1776, Thomas Jefferson was doing more than just signing the Declaration of Independence – he also was buying a thermometer for £3-15 in Philadelphia from merchant John Sparhawk. The author of the document that started the United States of America bought nearly 20 of the instruments over his life.
Just three days prior, on July 1, Jefferson began his first “meteorological diary.” From then on his daily routine included checking a thermometer at dawn and in the late-afternoon and recording the readings. Occasionally he would also use a barometer and hygrometer to supplement his measurements.
Jefferson believed that to understand the climate measurements would need to be taken across the young nation and he tried to spur others to do the same. He wrote that documentation would require “steady attention to the thermometer, to the plants growing there, the times of their leafing and flowering, its animal inhabitants, beast, birds, reptiles and insects; its prevalent winds, quantities of rain and snow, temperature of mountains, and other indexes of climate.”
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