Past IEM Features tagged: low

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High and Low Distributions

25 Apr 2017 05:35 AM
High and low temperatures on Monday were on the mild side of average with lows generally in the mid 40s and highs in the mid to upper 70s. The featured chart presents histograms for April 24th highs and lows based on period of record observations from long term Iowa climate sites. The stepped line represents the actual distribution, while the dashed line is the simple normal distribution based on the mean and standard deviation. The high temperature distribution is slightly wider showing the increased variability over low temperatures for this time of year.

Voting:
Good: 4
Bad: 0
Abstain: 1

Tags:   high   low  

Mostly Record Highs

06 Mar 2017 05:34 AM
The pleasantly warm weather this weekend was a reminder of the record warm just a while back during February. During which time we were setting a number of new daily record high temperatures. The featured chart presents the record high and low temperature set dates and beat margin. These events are computed as they are established with the passage of time. For example, records set in the 1940s may no longer still be records today, but are included in this chart. Anyway, the point of the plot is to show that recently we have certainly seen a larger share of record high temperatures set vs record lows.

Voting:
Good: 15
Bad: 2

Tags:   high   low   record  


Wind Direction

27 Oct 2016 05:40 AM
The featured chart displays a time series of wind direction reports from all automated airport weather stations in the state. A low pressure system moved over the state yesterday and a high pressure system settled into the state overnight. The impact of both systems on the distribution of wind direction reports is interesting to look at! The chart shows consistent wind direction reports on Tuesday from the east and southeast. The circulation around the low pressure system on Wednesday spread all the reports to show all directions reported at the same time in the state. The high pressure overnight effectively reversed all those reports as the circulation is opposite. Kind of neat!

Voting:
Good: 10
Bad: 0

Tags:   low   high   wind  

Biggest Step Down

04 Nov 2014 05:45 AM
The coldest air of the season arrived this past weekend with low temperatures in the 20s for most of the state. This bested the previously coldest temperature by around 10 degrees. The featured chart presents the largest "step down" in low temperature each fall season. The "step down" being the amount a new daily low temperature was colder than the previous fall minimum for that year. Rewording, if our current fall minimum temperature is 20 degrees, we probably would not expect to see a sub zero temperature until we had another day down to 10 degrees first.

Voting:
Good: 15
Bad: 8
Abstain: 10

Tags:   low  

Common Temperatures

18 Sep 2014 05:47 AM
The featured chart presents the frequency of daily high and low temperature combinations for Ames. The largest frequency to have a high of 84 to 86 and a low of 60 to 62, which is roughly the climatology for much of the summer season. The chart shows an interesting artifact around the freezing mark with higher frequencies showing up just below freezing for the daily low temperature. It is relatively more common to have a low temperature just below freezing than to have one just above. The reason being during the cold season with snow on the ground and/or cold soils, the temperature will often drop to below freezing after a daytime temperature above freezing. Restating, it is difficult for the air to maintain a warm temperature at night when the soil and/or snow are at sub-freezing temperatures.

Voting:
Good: 13
Bad: 6
Abstain: 4

Tags:   high   low  

3 Degrees in August

08 Aug 2014 05:44 AM
Temperatures were again a struggle on Thursday with highs near 70 instead of our average near 85! For Des Moines, the high temperature was only 71 with a low temperature of 68. This three degree difference between the high and low was the smallest such difference on record for the site for August. The featured chart presents the smallest difference in daily high and low temperature by month. The "largest" values are during the summer time when it is extremely difficult to prevent the sun from even slightly heating the ground. The forecast looks cool and dry, which should make for great Iowa State Fair weather!

Voting:
Good: 18
Bad: 10
Abstain: 12

Tags:   high   low  

No freeze yet

08 Oct 2013 05:37 AM
This is about the time of year by which much of Iowa has experienced its first freezing temperature. The featured chart presents the year to date lowest temperature after 1 July climatology for Ames. While not strictly the same metric, the intersection of the black line (average lowest temperature to date) and dashed line (freezing temperature) around this time approximately matches the average first freezing temperature of the fall. The minimum to date temperature for this year shows that we are well on the warm side of long term average. The shaded areas represent the percentile ranges of 50% and 95% of the daily data. The red line should remain flat for at least the next seven days with low temperatures well above 40 degrees.

Voting:
Good: 46
Bad: 16

Tags:   fall   freeze   low  


Only initial date of record event is shown and hourly ties were not considered

Time of Record Temps

10 Nov 2012 01:35 PM
Very warm air is surging into Iowa this Saturday with numerous record high temperatures being set. Des Moines set its record high today by reporting 78 degrees at 12:35 PM. Is it unusual for a record high to be set just after noon? The featured chart provides an estimate of the time of day record high and record low temperatures occurred at. The daily records are from a different dataset than the hourly temperature archive, so some estimates were done and a constraint that the extreme hourly temperature was within 4 degrees of the record temperature. Having a record high near 1 PM has happened previously, but that won't put a damper on today.

The lone blue dot (record low) shown at 5 PM on 25 Sep 1942 appears to be legitimate estimate.

Voting:
Good: 42
Bad: 13

Tags:   record   high   low  



Biggest Changes

21 Feb 2011 09:38 PM
Recently, Bartlesville Oklahoma went from a low temperature of -28 F on the 10th of February to a high temperature of 82 F on the 17th. This is a remarkable 110 degree change on the seventh day. Can any site in Iowa compete with this? The featured chart presents an IEM computation of historical climate data in Iowa and the largest value is 106 degree change on the 9th day. This happened during a remarkable period in February 1930 for Webster City after a low temperature of -34 was followed by highs in the 60s and then 72 on the 24th. Please note that the number for the 0th day is simply the difference between the high and low temperature (Tripoli 18 Jan 1996).

Voting:
Good: 13
Bad: 3

Tags:   climate   high   low   extreme  


Daily High & Low Correlation

05 Feb 2011 05:46 AM
The featured chart presents the daily computed correlation between the high and low temperature. Higher values imply a closer relationship between changes in highs and lows. For example, a cold low temperature would typically imply a cold high temperature for that day. There is a clear annual signal shown, but the question is what causes it... One reason may be that the increase in moisture and warming soil temperatures cause overnight lows to moderate and not vary as much. Another potential explanation is that air masses dominate in the winter season and perhaps that causes highs and lows to be more regular. What do you think? Feel free to comment on this via facebook!

Voting:
Good: 20
Bad: 7

Tags:   climate   high   low  


click image for better view

How fleeting are hot or cold days?

07 Jan 2011 05:56 AM
The featured chart presents the average temperature departure from average after a day that has either a high temperature two standard deviations (two sigma) warmer than average or a low temperature two sigma colder than average. You could think of this plot as examining how persistent really warm or cold days are. The plot is divided up by seasons showing how warm temperatures in the summer time tend to stick around longer than in the other seasons. Warm weather in the winter time is not as fleeting as one might have expected. Cold weather tends to stick around slightly more in the winter time than other seasons. Very cold air is set to arrive this weekend and stick around for most of next week.

Voting:
Good: 20
Bad: 7

Tags:   climate   high   low   extreme  


Where to find the coldest weather?

05 Oct 2010 06:57 AM
Yesterday's feature looked at the warmest spots in the state and today's feature shows the favored spots in the state with the lowest daily minimum temperature. This plot nicely shows some topographic effects that even occur in a flat state like Iowa. Northeast Iowa is the relatively cool, but the observation sites in the Mississippi River valley are sheltered some by the warm water during the fall season. Northwest Iowa is another location and it extends down into westcentral Iowa along the Nishnabotna Valley.

Voting:
Good: 23
Bad: 6

Tags:   low  


Years since the record

13 Sep 2010 05:55 AM
The featured chart presents the number of years since the record high or low temperature was set for Ames. Ties were not considered. Ames went another meteorological summer without setting a record high temperature. One has to go back to 1988 to find the last record high for Ames during June, July, and August. For July, the youngest record for high temperature was back in 1955! No records are in the forecast for this week.

Voting:
Good: 18
Bad: 3

Tags:   climate   high   low  


Record rainfall and temperatures

08 Apr 2010 05:12 AM
Roughly a week ago, some places in Iowa were setting records for warmest temperatures and then with the most recent storm, record rainfall. The featured chart looks at the frequency of having a record temperature around the days of having a record daily rainfall based on data for Ames. You can see how record maximum high temperatures frequently occur before a record rainfall as very warm air masses would imply stronger fronts, which should help produce higher rainfall amounts (as what recently happened). Record minimum highs (cold) also appear to be a common after a record rainfall. The climatology for any of the days shown on the chart would be one record.

Voting:
Good: 29
Bad: 10

Tags:   climate   high   low  


Hope for warming

03 Feb 2010 06:10 AM
The featured graph displays the difference in climatological average high and low temperature for Ames between the first and the last of the month. Positive values would indicate that the trend for the month is warming. The ten degrees of warming shown for February would feel nice right about now with bitterly cold air once again settled into the state. Some warmer weather is in the immediate forecast, but with the chance of more winter storms.

Voting:
Good: 20
Bad: 6

Tags:   high   low  


Note: the 1890s decade only had 7 years of data

Records by decade

04 Jan 2010 07:28 AM
The end of 2009 also brought the end of the first decade of the 21st century. The featured graph looks at the number of days per decade our current set of daily high and low temperature records consists of. Roughly 1/3 of our current daily high temperature records occurred during the 1930s and most of our daily low temperature records occurred before the 1950s.

Voting:
Good: 15
Bad: 7

Tags:   climate   high   low  


Days are not double counted if there was both a two sigma high and low on a given day.

Two Sigma Weather

22 Oct 2009 06:12 AM
The featured chart plots the number of days per year that experienced a high or low temperature exceeding two standard deviations from average for Ames. For example, some of last week's cool high temperatures in the 40s were two sigma below average. This chart is an attempt to quantify how "extreme" a given year was. In general, the highest values were prior to 1940 which is probably a reflection of the data quality for that period, although the very hot years in the 1930s show up nicely in this chart.

Voting:
Good: 14
Bad: 5

Tags:   high   low  


Best chance for warmer days

10 Apr 2009 06:17 AM
The featured chart is the percentage of days per month that experience either high or low temperatures at least 1 degree warmer than the previous day. April has the largest value for high temperature, but is just a mere few percentage points larger than October which only equates to approximately 1 more day per month. This chart would imply that climatology does not have a strong influence on actually seeing our day to day temperatures warm. Day to day temperatures are more strongly influenced by the passage of air masses.

Voting:
Good: 22
Bad: 18

Tags:   climate   high   low