DOWNLOAD PDF ANALYSIS OF EXTREME PRECIPITATION EVENTS IN SOUTHERN NEVADA

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1 Chapter 1 : Darryl Randerson Open Library Note: Citations are based on reference standards. However, formatting rules can vary widely between applications and fields of interest or study. The specific requirements or preferences of your reviewing publisher, classroom teacher, institution or organization should be applied. For extended analysis of regional temperature and precipitation patterns,as well as extreme events, please see our full report that will be released on February 11th. Significant climate events for January January was warm and dry overall for the contiguous U. This ranked as the 24th warmest January in the record and marked the warmest January since The average contiguous U. Most of the Lower 48 was drier than average, with drought worsening in parts of the West and Midwest. No state was record warm for the month. Parts of the Southern Plains and Northeast were cooler than average while no state had a top 10 cool January. According to preliminary data, during January, there were 3, warm daily temperature records broken or tied 1, warm maximum and 1, warm minimum, compared to cool daily temperature records broken or tied cool maximum and cool minimum. Most areas of the U. The Southern Rockies and Plains and the coastal Mid-Atlantic were wetter than average, but no state had a monthly precipitation value ranking among their 10 wettest. California had its fourth driest January, with 15 percent of average monthly precipitation. This was the third consecutive January with much-below-average precipitation for the state, which is typically the wettest month of the year. Several cities in northern California were record dry, including San Francisco, which received no measureable precipitation in January for the first time on record. January is also climatologically the wettest month of the year for San Francisco, according to the normals. This marked the 18th smallest January snow cover extent in the year period of record. Boston, Massachusetts, received The storm was rated a Category 3 "Major" for the Northeast, based on the Regional Snowfall Index that considers both the snow amount and population affected across the region. According to the February 3rd U. Drought Monitor report, Drought conditions also worsened for much of the Hawaiian Islands. For extended analysis of regional temperature and precipitation patterns, as well as extreme events, please see our full report that will be released on February 11th. Page 1

2 Chapter 2 : Precipitation Change in the United States - Climate Science Special Report Books by Darryl Randerson, Analysis of extreme precipitation events in southern Nevada, Characterization of cloud-to-ground lightning flashes on the Nevada test site. Information provided by the Northeast Regional Climate Center The Northeast experienced its second warmest August on record with an average temperature of All twelve states in the region recorded average temperatures this month that were above normal. Maryland experienced its third warmest August, followed by New York with its fourth warmest, and Pennsylvania recording its sixth warmest on record. Temperature departures for the month ranged from 4. This summer was also warmer than normal for all twelve states in the Northeast. With an average temperature of Rhode Island experienced its warmest summer on record, with a temperature departure of 2. Each state ranked this summer among their twenty warmest on record: The Northeast received 5. On average, Maine and Vermont were slightly drier than normal, but the other states in the region recorded a wetter-than-normal August. Pennsylvania ranked this as its ninth wettest August on record. With an average of After receiving an average of Maryland experienced its fourth wettest summer, and West Virginia had its seventh wettest summer on record. Summer precipitation departures ranged from 6. Dry conditions improved across the Northeast as the month progressed. At the beginning of August, dry conditions were largely present in northern New York and New England. Abnormal dryness was impacting 18 percent of the Northeast, and 10 percent of the region was in moderate drought. Abnormal dryness eased in much of New Hampshire and southern Maine throughout the course of the month. By the end of August, 13 percent of the Northeast was abnormally dry and seven percent of the region was experiencing moderate drought. Heavy rain led to flooding in parts of Pennsylvania, New York, and New Jersey throughout this past month. On August 2, an EF-0 tornado touched down in Queens, New York, damaging a few homes and downing trees and power lines in its short path, but no injuries were reported. Severe weather moved through New England a few days later on August 4, resulting in minor damage from an EF-0 tornado that moved through in Windham County, Connecticut. Later that same day, an EF-1 tornado in Webster, Massachusetts led to structural damage downtown and displaced about 30 residents from their homes. These storms caused more than 9, customers to lose power. Fallen trees damaged homes in Selden, New York and house fires were reported from lightning strikes associated with these powerful storms. Railroad services were suspended across parts of Long Island and more than 10, customers were without power that night. On August 13, Lakewood, New Jersey received 8. In Seneca County, New York, a similar sequence of events occurred during that same time frame. Hector, New York recorded 6. Road closures were reported along coastal New Jersey and in southern New York that same week as rivers started to overflow their banks, prompting a state of emergency to be issued in many of those areas. The severe storms on August 15 caused a mandatory boil water order to be in effect for nine days and resulted in the cancellation of the Phish Festival in Watkins Glen, New York due to the unavailability of clean drinking water for the 30, people that were expected to attend. Flooding in Lancaster County, Pennsylvania on August 21 resulted in closed parks and roadways as streets became flooded. An EF-1 tornado touched down in Brockway, Pennsylvania that same day, and was on the ground for about four miles, but no injuries were reported. Information provided by the Midwest Regional Climate Center Precipitation in August was a mix of above and below normal rainfall. All nine Midwest states had areas with both above and below normal totals. The driest areas in August were in north central Minnesota where less than half the normal rain fell. Other areas with less than 75 percent of normal were in Minnesota, eastern Upper Michigan, and near the confluence of the Ohio and Wabash rivers at the southwestern tip of Indiana. Scattered pockets of rainfall more than two times normal were scattered across every Midwest state except Minnesota. Region wide, rainfall was percent of normal with statewide totals of 89 percent in Minnesota and above normal values in the other eight states. Totals ranged from percent of normal in Michigan to percent of normal in Missouri. Very heavy rains fell on the 20th and 21st just to the west of Page 2

3 Madison, Wisconsin with unofficial reports of 11 to 15 inches to mm which would exceed the hour record for the state. The Wisconsin record was set on June 24, near Mellen, Wisconsin with Daily precipitation records were set over times during August. Each state had at least 30 such records with in Wisconsin, 95 in Iowa, and 88 in Illinois. Summer precipitation was also a mix of above and below normal values. Summer values ranged from just under 75 percent of normal to nearly twice normal. August temperatures were near normal in the western and southern portions of the region and slightly above normal in the northeastern sections. Temperatures averaged 2 to 4 degrees F 1 to 2 C above normal in much of Lower Michigan and the northeastern half of Ohio. Minimum temperatures were above normal for much of the Midwest with only Iowa and northwestern Minnesota near normal for August. Minimum temperatures were 4 to 5 degrees F 2 to 3 C above normal in parts of Lower Michigan and northeastern Ohio. There were few extreme temperatures, just 57 daily record high maximums and 46 record low minimums, but there were numerous record low maximums and record high minimums mostly in the last week of the month when heavy rains were falling. Drought in August was mainly focused on two regions. The first was Missouri and southeastern Iowa where extreme and exceptional drought were reported throughout August. The other region was in Lower Michigan where widespread moderate drought and even some severe drought were reported. Drought peaked in mid-august at just under 20 percent of the Midwest and over 80 percent of Missouri. In Missouri, extreme drought covered more than 25 percent of the state and exceptional drought covered more than 5 percent of the state. Rains late in August brought those numbers down slightly as the month came to a close. Flooding and flash flooding occurred at numerous locations throughout the month of August as heavy rains fell in numerous locations during August. Some of the worst flooding was in southern Wisconsin. There was possibly a Wisconsin state record for hour precipitation set west of Madison on the 20thst and then heavy rains in the last week of the month across southern Wisconsin. Some areas were hit with rainfall totals that matched their normal totals of all of July and August in just a few days. There were evacuations, record flood stages, interrupted Amtrak services, cancelled classes, and six counties were declared in a state of emergency. Roads were closed for days due to flooding and some washouts. Tornadoes were reported in the Midwest on 13 days including clusters of reports on the 19th in southwestern Missouri and on the 28th in central Wisconsin. There were 17 confirmed tornadoes in Wisconsin on the 28th with the strongest rated as EF-2 on the enhanced Fujita scale. Damage to trees and agriculture was widespread but there were no reported fatalities or injuries. Hail was reported on 21 days in August and wind damage was reported on 25 days. For further details on the weather and climate events in the Midwest, see the weekly and monthly reports at the Midwest Climate Watch page. Temperatures were most above normal across far eastern Virginia and northeastern North Carolina, with observed temperatures degrees F 1. Cape Hatteras NC ; tied for first warmest reported a mean temperature of Norfolk VA ; tied for fourth warmest reported a mean monthly temperature of The coolest temperatures in the Southeast were found in western Georgia and parts of Alabama, where frequent precipitation and clouds helped keep daytime temperatures low. Because of the humid conditions, maximum temperatures across the region were generally a little below average while minimum temperatures were slightly elevated, except in the areas with the warmest conditions in Virginia and North Carolina. Only six stations reported maximum temperatures ranked in the top three warmest in August compared to 13 locations, which reported average monthly minimum temperatures in the top three warmest. Fairhope AL ; first coldest reported a minimum temperature that was 3. The highest daily maximum temperature of degrees F No other station in the Southeast reported a temperature exceeding F Mount Mitchell NC reported the lowest daily temperature across the region during the month with 39 degrees F 3. These cool temperatures occurred in the wake of a cold frontal passage, which brought much-appreciated relief from the hot and humid conditions. Many stations in the Southeast observed their coldest temperatures of month during this period. Precipitation was highly variable across the Southeast in August, as is common during the summer. The driest areas included most of the Florida peninsula and South Carolina, and eastern Georgia. Dry conditions were also noted in far eastern Virginia and North Carolina, where the hottest conditions occurred, as noted above. Manteo Airport ; second Page 3

4 driest in far eastern North Carolina reported 1. Two other long-term stations in Brunswick GA and Andrews SC reported amounts that were the 5th driest for their locations. The areas that were most above normal in precipitation included the Appalachian Mountains, central North Carolina and Virginia, western Georgia, and eastern Alabama. Most of western North Carolina and Virginia as well as parts of western Georgia and southeastern Alabama reported amounts that were percent of normal precipitation this month. In those areas, 21 long-term stations observed precipitation totals that were ranked within their five highest values on record. Asheville NC reported As is typical of August, localized heavy rainfall produced flash flooding across parts of the region. Thunderstorms that began on the evening of July 31 and continued into August 1 brought precipitation amounts of over 4 inches in a hour period to Albemarle County in Virginia and surrounding counties. Flooding from the heavy downpours resulted in numerous water rescues from cars that drove through water-covered streets. On August 11, Naples FL reported 3. Atlanta GA received their 5th wettest one-day August rain with 3. In general, the wettest periods were from August 1 to 4 and August 19 to 23 as strong cold fronts approached the area. The driest period occurred between August 24 and 29, as a strong ridge of high pressure was positioned over the area. There were severe weather reports across the Southeast during August, which is percent of the median monthly frequency of reports during At least one severe weather report was recorded in the region on 25 days during the month. Page 4

5 Chapter 3 : Summary Information State of the Climate National Centers for Environmental Information (N Randerson, D., Analysis of Extreme Precipitation Events in Southern Nevada. NOAA Technical Memorandum ERL ARL, National Oceanic and Atmospheric Administration, Silver Spring, Maryland. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use Bioretention to collect stormwater runoff Bioretention is an adapted landscape feature that provides onsite storage and infiltration of collected stormwater runoff. Stormwater runoff is directed from surfaces to a shallow depression that allows runoff to pond prior to infiltration in an area that is planted with water-tolerant vegetation. As runoff accumulates, it will pond and slowly travel through a filter bed pictured on the right where it either infiltrates into the ground or is discharged via an underdrain. Small-scale bioretention areas are often referred to as rain gardens. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use Blue Roof to hold precipitation after a storm event and discharge it at a controlled rate A blue roof is designed to hold up to eight inches of precipitation on its surface or in engineered trays. It is comparable to a vegetated roof without soil or vegetation. After a storm event, precipitation is stored on the roof and discharged at a controlled rate. Blue roofs greatly decrease the peak discharge of runoff and also allow water to evaporate into the air prior to being discharged. The water can either be slowly released to a storm sewer system or to another GI practice such as a cistern or bioretention area. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use Permeable pavement to allow runoff to flow through and be temporarily stored prior to discharge Permeable pavement includes both pavements and pavers with void space that allow runoff to flow through the pavement pictured left. Once runoff flows through the pavement, it is temporarily stored in an underground stone base prior to infiltrating into the ground or discharging from an under drain. Permeable pavers are highly effective at removing heavy metals, oils, and grease in runoff. Permeable pavement also removes nutrients such as phosphorous and nitrogen. Soil and engineered media filter pollutants as the runoff infiltrates through the porous surface. The void spaces in permeable pavement surfaces and reservoir layers provide storage capacity for runoff. All permeable pavement systems reduce runoff peak volume. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use Underground storage systems to detain runoff in underground receptacles Underground storage systems vary greatly in design. Underground storage systems detain runoff in underground receptacles that slowly release runoff. Often the underground receptacles are culverts, engineered stormwater detention vaults, or perforated pipes. One of the benefits of underground storage is that it does not take up additional surface area and can be implemented beneath roadways, parking lots, or athletic fields. Underground storage systems are typically designed to store large volumes of runoff and therefore can have a significant impact in reducing flooding and peak discharges. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use a stormwater tree trench to store and filter stormwater runoff A stormwater tree trench is a row of trees that is connected by an underground infiltration structure. At the ground level, trees planted in a tree trench do not look different than any other planted tree. Underneath the sidewalk, the trees sit in a trench that is engineered with layers of gravel and soil that store and filter stormwater runoff. Stormwater tree trenches provide both water quality and runoff reduction benefits. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use a retention pond to manage stormwater A retention pond is one of the earliest prototypes of GI, and is now considered a more traditional type of stormwater infrastructure because it has been integrated into gray infrastructure design. It is an engineered stormwater basin designed to store runoff and release it at a controlled rate while maintaining a level of ponded water. Pollutants and sediment loads are reduced as the runoff is retained in the basin. Retention ponds are a very common stormwater management practice and may be designed with sustainable elements to increase water quality and decrease peak discharges. Vegetated forebays may be added to increase sediment removal as well as provide habitat. Another enhancement to traditional stormwater retention ponds is the addition of an ironenhanced sand filter bench that removes Page 5

6 dissolved substances such as phosphorus from runoff. Stormwater Management and Water Quality Apply Green Infrastructure Strategies Use extended detention wetlands to reduce flood risk and provide water quality and ecological benefits Extended detention wetlands, such as the one shown in the figure on the right, may be designed as a flood mitigation strategy that also provides water quality and ecological benefits. Extended detention wetlands can require large land areas, but come with significant flood storage benefits. Extended detention wetlands can be created, restored from previously filled wetlands, or enhanced existing wetlands. Wetlands typically store flood water during a storm and release it slowly, thereby reducing peak flows. An extended detention wetland allows water to remain in the wetland area for an extended period of time, which provides increased flood storage as well as water quality benefits. Stormwater Management and Water Quality Build Staff Capacity Provide training for municipal staff on green infrastructure Training can help to better equip staff to assess green infrastructure proposals. EPA and other federal agencies and nongovernmental organizations have formed the Green Infrastructure Collaborative, a network to help communities more easily implement green infrastructure. Page 6