Lake Havasu City 2010 Weather Summary, Lecture notes of Life Sciences

Download Lake Havasu City 2010 Weather Summary and more Lecture notes Life Sciences in PDF only on Docsity! Lake Havasu City 2010 Weather Summary Doyle Wilson, Water Resources Coordinator The four weather stations tracked by the city year-round are located at the Public Works Maintenance Facility (PWMF) on London Bridge Road (elev. 472 feet), at City Hall (elev. 730 feet), at Mohave Community College (MCC) (elev. 640 feet) and at fire Station #5 on Lake Havasu Avenue north of Mesquite Avenue (elev. 503 feet). The PWMF site data is what is sent to the National Weather Service everyday and the MCC station is monitored by AccuWeather. More detail of these stations is given in the 2006 summary report. A combined average is compiled for high and low temperature and for precipitation amounts from the four stations. Three of the stations record peak wind speeds and a monthly combined average is also calculated. 2010 began with the culmination of a moderately strong El Nino event with higher than normal winter precipitation and definitely cooler temperatures than normal well into the late spring. This transitioned into La Nina conditions in the late summer, which strengthened through to the end of the year. As described in last year’s summary report, La Nina conditions do not necessarily have a major affect on the region’s weather. Temperatures A moderately strong El Nino (warmer than normal equatorial seawater surface temperatures (SST) off the west coast South America) ushered in the New Year keeping temperatures down through June, but waned and was replaced by a growing La Nina (cooler than normal SST) condition through the end of the year. El Nino implications to the Lake Havasu area are explained more fully in last year’s summary report, but briefly, this phenomenon tends to produce cooler than average temperatures from winter through late spring. Past Lake Havasu City temperature and rainfall data indicate that La Nina conditions do not force a significant difference from normal conditions. 2010 High and Low Average Daily Temperatures 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 12/13/2009 2/11/2010 4/12/2010 6/11/2010 8/10/2010 10/9/2010 12/8/2010 D eg re es F 2010 Ave. Highs 2010 Ave. Lows Figure 1: 2010 high and low temperature profiles for Lake Havasu City. The month of May was the coolest May since 1980 and the second coolest on record with a four station high temperature average of 89.3oF. The 1980 average came from only one station, which was located at the former Island Airport. The average low temperature for May was also cooler than normal at 65oF, which was the first time it was this low since 1991. May 23rd reached a record low 56.4oF at the City Hall weather station. The previous low record for this date was 64oF set in 1996. April also had the coolest low temperature average for an April since 1999. Cold fronts were passing through the area on a regular basis in April and May bringing in cooler than normal air temperatures. September, on the other hand, was the second warmest on record (since 2001) with a four station average of 104oF. September 27th tied a record high of 108oF for that date. December was also the warmest since 2000 at 66.1oF even though the last week of the month cooled down considerably. Also the average low temperature for December was the highest on record at 47.8oF, but the month also included a tie for the lowest temperature of the year, which occurred on December 31st at 33.1oF (It was the second time this year that the thermometer reached this value (12-27-2010). The month of February also had one of warmest low temperature averages for that month since 2000. December was rather manic in that three of several cold fronts, besides bringing in rain, timed their passage so that successive daily lows and daily highs occurred within a few hours of each other: 12-15 to 12-17: The weather system that passed through on the 15th was evidently a combination of first a warm front and later a cold front. The low for that day was at 2:30am and the first front passed through at 3:30am, when the barometric pressure was at its lowest, but the temperatures began to rise. Later that day at 5:00pm the winds shifted Comparison of Monthly Precipitation Bewteen 2010 and the 40-year Average 0.00 0.50 1.00 1.50 2.00 2.50 P re ci pi ta tio n ( in ch es ) 2010 Ave. 40-year Ave. Jan Mar May July Sep Nov Dec Figure 3: Average monthly rainfall (over four stations) for 2010 compared with the City’s 40-year monthly averages. Figure 4: Storm flooding from the October 20th rain event. Most of the water probably came from the Mohave Mountains as the storm cell was centered over that area. Figure 5: A Cut-off low pressure air mass from which a tiny storm cell grazed passed the east side of the city on October 20th, but produced flooding within the city. Lake Havasu City 2010 Monsoon Season Monsoon season was remarkable only in its inability to bring in rain, but it was typically humid and sticky. Moreover, it did not last long and was broken up by periods of drier air especially in early September before returning in late September and October. Almost no rain fell until the first part of September, but only averaged 0.06” from four weather stations for the one storm event that did occur. Dew Point Temperatures Very low dew point temperatures, those in the single digits or below zero, indicate very dry air masses (they are actually called frost points when below 32oF). Relative humidities are also low when dew points are very low, but not necessarily single digits. Lake Havasu City usually experiences these conditions in June and the first of July prior to monsoon season, but in 2010 the only single digit dew point temperatures in the first half of the year was for four one-half hour intervals on July 2nd during the late afternoon and early evening. The lowest value was 3.4oF (relative humidity at 2%) when the outside temperature was 109.6oF. The next single digit dew point temperatures did not occur until the late evening of November 24th. The dry air mass stayed over Lake Havasu City for another day and a half with the lowest dew point at -3.4oF (relatively humidity at 11%) with an outside temperature of 49oF. The only dew point temperature lower than this for 2010 occurred on New Year’s eve, at -5.3oF (relative humidity at 11%) with an outside temperature of 46.5oF. Peak Wind Speeds Peak wind speeds recorded every 30 minutes are averaged over each month to compare general wind conditions over the course of a year. There are three weather stations in the city that generate peak wind data and these are averaged together each month. Wind conditions for the first half of 2010 normal when compared to the average over the last eight years, the span of available documentation. July was the windiest month followed closely by June, April and May (Table 1). The second part of 2010 was a little different with August peak winds averaging one per hour faster than the eight year average, September experienced a one mile per hour decrease and November an amazing 2.5 miles per hour increase. This November was quite different from other documented Novembers in that the barometric (air) pressure record indicates that more fronts with a significant pressure change between the high and low pressure centers passed through the area even though no rain was associated with any of them. The greater magnitude of pressure difference between the high and low centers and the closer they are to each other will yield increasing wind speeds. November 2010 had at least five and maybe even seven low pressure fronts with four having significant pressure changes (Figure 6). Month 2010 8-year Average January 8.13 8.74 February 8.18 8.57 March 9.48 9.25 April 10.58 10.88 May 10.80 10.64 June 11.08 10.97 July 11.40 10.88 August 10.73 9.72 September 6.89 8.79 October 8.84 8.56 November 9.95 7.48 December 7.91 8.02 Average 9.57 9.37 Table 1: Peak wind speed averages in Lake Havasu City for each month in 2010 and over an 8-year average. The overall averages are comparable, but the second half of 2010 contains departures from the norm.