ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1849 Ft. Snelling climatological record consists of: four daily fixed time readings taken from the station's "detached" thermometer; daily precipitation values; four daily fixed time sky cover observations; four daily fixed time observations of wind "force" and wind direction; two daily fixed time wet bulb readings; four daily barometric readings; and four daily readings from the station's "attached" thermometer (i.e. from an indoor thermometer used to adjust barometric readings for the effects of temperature on the station's mercury barometer) . Temperature, sky cover, wind direction/force and barometric observations were taken at or about local sunrise, at or about 0900 hours, at or about 1500 hours and at or about 2100 hours local solar time. Wet bulb readings were taken at local sunrise and at 1500 hours local time. Although extant records give no explicit indication of the time at which 1849 precipitation observations were taken, contextual evidence suggests either a 2100-2100 schedule and/or an early morning (probably "sunrise") schedule (which, in at least in some instances, may have entailed "shifting" of precipitation values from the date on which the observation was actually made to the day immediately preceding).
So far as can be determined, 1849 Ft. Snelling temperature readings were taken from an instrument manufactured by George Tagliabue, New York City and precipitation observations were taken from a DeWitt rain gauge (which was probably mounted on a pole or post on the fort's parade ground). Unfortunately, however, many of the 1849 readings taken from these instruments are problematic, the apparent result of haphazard and/or deficient observational and recording practices and/or poorly preserved/semi-legible copies of original records . Specifically, 1849 temperature records contain several obvious transpositions (e.g. 31 written as 13); numerous errors involving computation of daily and monthly AVERAGES and/or values blocked out or obscured by poor quality microfilm. Any such shortcomings are, however, comparatively minor when considered in the context of the quality of the 1849 precipitation record. Contextual evidence suggests, for example, that many daily precipitation values were entered by clerks who, because they did not understand decimal notation, confused inches and tenths of inches, leaving a legacy of entries which are open to several different, but equally plausible, interpretations. In other instances, daily precipitation values do not add to the monthly totals entered in the "precipitation total" columns on the station's monthly meteorological registers. In still other instances, monthly precipitation totals seemingly bear little relationship to the monthly records in which they appear. And, in still other instances, fort observers appear to have measured precipitation several times daily and, instead of entering an aggregate total, entered several individual values in the record for any given
day (e.g. .11.12 rather than .23).
The result is a hopelessly confused and apocryphal record, specific examples of which include:
_ Conflicting January 1849 precipitation totals. Daily January values, as recorded by Fort observers, add to a meager 0.10 inches. Yet, the entry at the bottom of the station's January 1849 meteorological register indicates a monthly total of 1.00 inches, a value subsequently used in several early Twin Cities climatological summaries (including those prepared by the Surgeon General, the Army Signal Corps and the U.S. Weather Bureau). Extant records are silent as to the reasons for this discrepancy: there are, however, several possible -- but highly speculative -- ways in which it might be explained: a) that a substantial portion of the precipitation which fell during January 1849 was recorded on forms which have since been lost or discarded; b) that the one inch value is a snowfall estimate derived by applying the 1:10 rule (0.10 x 10 = 1.00); or c) that the one inch value is the result of a misplaced decimal (probably one of many such recording/copying errors made in 1849 by clerks who did not understand decimal notation). On balance, however, available evidence establishes the 0.10 inch total as the only credible January 1849 precipitation value -- a value which, accordingly, has been used in preparation of this compilation.
_ An apparently incomplete/inadequately documented February 1849 precipitation record. Although recorded precipitation totaled only 0.01 inches, many early climatological summaries (Signal Corps, U.S. Weather Bureau, etc.) give a monthly total of 0.61 inches. Extant records are silent as to the source of the greater value. As in the instance of the January 1849 record, there are, however, several ways in which such a discrepancy might be explained: a) that the clerks who transcribed precipitation totals from original records to the Ft. Snelling climatological record read 0.01 inches as 0.61 inches (zeros, in the handwriting of many Ft. Snelling clerks, can easily be read as sixes); b) that a substantial portion of the precipitation which fell in February 1849 was recorded on forms which have since been lost or destroyed; or c) that, although unlikely, the greater value may be a monthly snowfall value. However, in addition to whatever amount of precipitation was actually measured by Fort observers during February 1849, extant records indicate several unmeasured precipitation events: an unrecorded amount of rain and snow during the night of 20-21 February and an ambiguous entry suggesting that unrecorded precipitation may have fallen during the night of 24-25 February . Consequently, as indicated in the accompanying compilation, the February 1849 precipitation record is assumed to be incomplete/partially missing.
_ A March 1849 precipitation total (4.11 inches) seemingly unrelated to the amount of precipitation (probably 0.67 inches) actually recorded by Fort observers during that month. Like the January and February 1849 values noted above, the higher March total appears in several early Minnesota-Twin Cities climatological compilations and, also like the seemingly aberrant totals for the previous two months, can be explained only if: a) it is assumed that significant amounts of precipitation were recorded on forms which were subsequently lost/discarded; or b) it is assumed that the higher value is a monthly snowfall value, not a meltwater value . There is, however, no tangible evidence to support these or any other similar conjectures. Consequently, the record probably "defaults" to the lower value.
_ A semi-legible and highly ambiguous May 1849 precipitation record. The station's May 1849 meteorological register gives a monthly total of 6.59 inches (or, on another reading, 6.57 inches), a value which, so far as can be determined, was derived by adding the daily values entered in the station's original May 1849 record. Unfortunately, however, several of these daily entries are muddled/unclear and, as a result, are open to any of several plausible interpretations. The 11 May precipitation entry could, for example, be construed either as 1.03 inches (as it is in the accompanying record) or as 1.30 inches. The most puzzling entry, however, consists of a virtually illegible 31 May precipitation value followed by a decimal point and accompanied by remarks indicating "slight rain". This entry could be interpreted in many different ways: perhaps as indicating rainfall of 2.00 or 3.00 inches or, given the accompanying remark suggesting "slight" rainfall (and assuming a misplaced decimal point ), perhaps as indicating only 0.30, 0.20, 0.03 or 0.02 inches of rain. Finally, when taken in combination, the 31 May and 11 May values (together with other ambiguous precipitation values in the May record) could be interpreted in such a way as to yield monthly precipitation totals ranging from 4.62 inches to 7.59 inches.
_ A July 1849 precipitation record which, like its May counterpart, contains several highly ambiguous entries. Microfilm copies of the original record indicate a 12 July precipitation value of 12.11 and an 18 July value of .11.32. So far as can be determined, these entries involve misplaced decimal points (to be interpreted, respectively, as 1.21 and 1.13 inches) or, alternatively, involve two separate measurements (to be combined into daily totals of 0.23 and 0.43 inches, respectively). The latter interpretation yields a monthly total of 4.41 inches: the first (and more expansive) interpretation yields a monthly total of 7.49 inches (neither of which correspond to the 7.59 inch value indicated in the original 1849 record, a value which, in turn, appears in several earlier climatological summaries prepared by the Surgeon General, the Army Signal Corps and the U.S. Weather Bureau).
_ An August 1849 precipitation record which, like the July 1849 record, appears to have been compromised by a combination of misplaced decimals and/or multiple, unaggregated daily measurements. The questionable entries include daily precipitation values for 9 August (originally entered as 11.19); 11 August (originally entered as 18.11); and 15 August (originally entered as 14.52). Like similar entries in the July record, these values can be interpreted, respectively, as 1.12 inches, 1.81 inches and 1.45 inches or as 0.30, 0.29 and 0.66 inches, respectively. The first interpretation yields a monthly total of 10.07 inches; the second interpretation yields a total of 6.53 inches (neither of which correspond to the earlier "official" value of 9.60 inches).
The dubious value of much of the 1849 precipitation record (particularly the aforementioned January, February, March, May, July and August records) obviously frustrates any attempt to determine the amount of moisture which actually fell (and/or which was recorded) during 1849. The foregoing 1849 climatological summary, accordingly, provides four different sets of precipitation values, none of which can be considered definitive (or perhaps even plausible). The first record is based largely on totals entered at the bottom of the precipitation column in the original 1849 record and, as such, is the record which, until recently, was considered to be "official". The second is a record reconstructed by Twin Cities consulting meteorologist Bruce Watson and published in the 1976 edition of the Twin Cities Weather Almanac. The third record was compiled in 1997 and involves an "expansive" interpretation of many of the ambiguous values found in the original 1849 record (e.g. the August 1849 entry of 14.52 is assumed to mean 1.45 inches). The fourth record (which in several instances corresponds closely to the 1976 Watson record) was also compiled in 1997 but, unlike record three, involves a "conservative" interpretation of ambiguous values (e.g. the August 1849 entry of 14.52 is assumed to reflect two individual measurements, the combined value of which is 0.66 inches).
All 1849 wind force values are expressed in terms of a numeric wind force value selected by the observer after visually noting the effect of wind on flags, trees, signs and other easily movable objects . The degree of cloudiness was similarly quantified, using a scale of zero (complete overcast) to ten (a totally cloudless sky) . In addition, 1849 records include notations indicating the total number of "fair" and the total number of "cloudy" days observed during each month of the year. Unfortunately, the terms "fair" and "cloudy" are nowhere defined: presumably, however, they refer to the general character of each day of the year, with "fair" probably indicating an essentially cloudless day and "cloudy" indicating an overcast or partially overcast day (thus probably including what, in modern terminology, would be recorded as "partly cloudy" days).
Unlike the 1849 daily sky cover record (which includes a complete set of daily entries), the force of wind record is typically incomplete: air movement records include a significant number of wind direction entries UNACCOMPANIED by corresponding quantitative wind speed indicators. Extant records give no explanation for these lapses: perhaps the missing entries indicate a force of wind value of more than zero but less than one or, alternatively, that fort personnel, for whatever reason, were unwilling or unable to expend the time and effort required to take consistent wind speed observations.
Like corresponding records from the years immediately preceding (and, given its obvious shortcomings, perhaps even to a greater extent than in previous years), the 1849 Ft. Snelling record appears to significantly understate the number of days with precipitation and/or measurable precipitation. This suggests that -- following the example of their predecessors -- Fort observers did not routinely/consistently measure and/or record small precipitation events, sometimes either ignoring less significant deposits of rain or snow (or. alternatively, using terms such as "inappreciable" or "slight" to denote small, but perhaps otherwise measurable, amounts of precipitation).
Although the 1849 Fort Snelling record includes daily liquid/melted precipitation values and a record of the TYPE of precipitation observed, it includes NO QUANTITATIVE snowfall values (whether of fresh snowfall or accumulated snow cover). Any snowfall values contained in the foregoing compilation, therefore, are estimates obtained by applying the National Weather Service meltwater-snowfall conversion matrix to the meltwater values recorded by Ft. Snelling observers on 1849 "snow days".
In addition to outdoor temperature, sky cover, precipitation and air movement data, the 1849 Ft. Snelling record includes four daily readings taken from the station's mercury barometer and from the "attached" thermometer (readings which, as noted above, were probably used to correct barometric readings for the effects of temperature on the mercury in the station barometer). So far as can be determined, 1849 barometric values are station pressures (i.e. readings which have not been adjusted to compensate for elevation above mean sea level).
Some parts of the 1849 Ft. Snelling temperature record may have been compromised by improper instrument exposure and/or erratic observational schedules. Specifically, fixed time temperature readings taken during the warm months of 1849 show inordinate "compression" of daily readings taken at 0900 and 1500 hours. This suggests, of course, that the station thermometer may have been exposed to the mid-morning rays of the late spring and summer sun and/or that observations were often taken at times significantly different from those indicated in the official record.
Beginning with the April 1849 debut of the Minnesota Pioneer, Ft. Snelling records are enhanced by journalistic accounts of St. Paul area weather events. These accounts often provide interpretive detail not found in the sparse and sometimes cryptic remarks in the Fort station's meteorological registers and, as such, are invaluable in checking and evaluating east central Minnesota's pioneer era records .
The foregoing 1849 climatological record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperature values. The unadjusted record consists, in turn, of two values: a) the simple averages of fixed time readings taken daily at sunrise, 0900, 1500 and 2100 hours; and b) the simple average of fixed time readings taken daily at sunrise, 1500 and 2100 hours only. Because it disregards the often anomalous 0900 hour readings, the second set of unadjusted averages illustrates the extent to which sun contamination may have distorted the 1849 Ft. Snelling temperature record. Adjusted averages are from Charles J. Fisk's 1984 "Reconstruction of Daily 1820-1872 Minneapolis-St. Paul Temperature Observations". These values were obtained by averaging statistically derived estimates of the daily maxima and minima which would have been recorded had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight . The foregoing 1849 record also includes both the monthly and annual extremes (highest daily minimum, lowest minimum, etc.) estimated by Fisk and the monthly extremes actually recorded by fort observers. All 1849 temperature distributions (e.g. days 90 F or higher, 32 F or lower, etc.) are based on Fisk's estimates of daily maxima and minima.
All foregoing monthly mean cloudiness values are the simple average of the station's four daily numeric sky cover entries. The foregoing prevailing wind values are based on daily entries indicating the direction of the wind at sunrise/0900/1500/2100: prevailing/predominate winds are those most frequently observed/recorded during any given month.
Cold, cloudy and apparently very dry January: sunrise readings of -25 F and -29 F on 10, 18 January, respectively. Force seven winds recorded on 12 January. Smoky atmosphere on 28 January. Twenty five "cloudy" days recorded during January. Very cold mid-February. Force six and seven winds on 17 February followed by a sunrise reading of -30 F on 18 February. "Storm wind" on 24-25 February. Readings of -37 F and -40 F noted by observers living in the vicinity of Ft. Snelling on 18 February. St. Paul journalist (writing in April 1849) described the winter of 1848-49 as "the severest known in the northwest for many years...the snow set in on the first of November and for that time until the commencement of the present month, hill and valley....presented an unvaried surface shrouded in the white mantle of winter....the winter was long and tedious but we had few storms...the cold was intense...". Ft. Snelling record indicates that very little snow fell during February. Temperate but apparently relatively dry March. "Very strong" winds on 11 March. All thirty one days of March classified as "cloudy". Wet, cloudy (thirty days classified as "cloudy") and cold April. Excessive rain from 0300 to 1000 hours on 2 April: 3.5 inches recorded. Local flooding on the Mississippi and Minnesota rivers on 4 April. Very windy during April. Force nine winds 12, 13, 30 April; force eight winds on 5, 9, 13, 16, 23, 24, 25, 30 April. "Very strong" winds (no wind force value given) on 7, 8, 9, 12, 28 April. April 1849, as described by a St. Paul journalist was "very rare even in this latitude...the wind blew in great violence from the north and northwest almost every day...the weather was exceedingly cold and disagreeable...the 7th of May was the first really spring day of the season...". Afternoon reading of 32 F on 30 April. Cold, wet and cloudy (all thirty one days classified as "cloudy" ) May. Readings of 24 F and 40 F at sunrise and 1500, respectively on 1 May. Force eight winds on 4, 21 May. "Vivid lightning and thunder" on 19 May. Rising river levels noted during early May. Cool, wet early June. Excessive rains on 4-5 June with part of the St. Paul bluff washed away: St. Paul newspaper noted that a "storm of rain commenced falling on Monday evening and continued almost without cessation until Tuesday night...": 1.9 inches of rain recorded at Ft. Snelling, 4-6 June. Afternoon readings of 56 F and 52 F on 4, 5 June, respectively. Force eight winds on 5, 6 June. Thirty days during June recorded as "cloudy". Wet, cloudy (thirty "cloudy" days) July. Warm early July with a sunrise reading of 78 F on 10 July. An unidentified St. Paul observer noted a temperature of 104 F on 12 July: 93 F recorded at Ft. Snelling on that date. Force eight winds on 3 July. Excessive rains, 17-18 July. Very wet and cloudy (twenty four "cloudy" days recorded) August. Excessive rains beginning at about 0900 hours on 7 August, continuing until about 1100 hours on 8 August: 5.3 inches of rain recorded by fort observers, 7-9 August. Afternoon reading of 64 F on 7 August. Force eight winds on 8 August. Afternoon reading of 62 F on 11 August. Cool late August: reading of 62 F at 1500 on 30 August. Warm September with no frost recorded. Very heavy rains early October: 4.06 inches recorded during rainstorm which began at 0100 on 1 October and ended at 2000 on 2 October. Temperatures in the 40's F and strong east winds on 2 October. Rising river levels noted on 3, 5, 15 October. Warm late October: reading of 70 F at 1500 on 31 October. Cloudy (twenty five "cloudy" days recorded) November. Reading of 72 F at 1500 on 1 November. Sunrise readings of 54 F, 54 F, 53 F, 54 F, 54 F on 1, 3, 4, 5, 16 November. Very little snow during November (1.5 inches recorded by C.N. Goddard in Stillwater). Record indicates that winds during November were generally light. Mild early December followed by severe cold after mid-month. Readings of -22 F and -11 F at sunrise and 1500, respectively, on 29 December. Stillwater observer (Goddard) recorded -25 F and -31 F at sunrise on 29, 30 December, respectively. Reading of -28 F recorded at 0900 on 30 December by an unidentified St. Paul observer. Ft. Snelling record indicates that December precipitation was heavy with snowfall perhaps approaching thirty inches. St. Paul journalists noted snow cover of "more than one foot" at the end of December: Stillwater observer, however, recorded only about thirteen inches of snow during the month.