Derecho Storm Facts.

Here are some of the facts that I have gathered about the horrific storms that ravaged the area last Friday afternoon.

Originally, the storms formed along a boundary that separated warm, moist air from warm, dry air to the north. The storms formed in far Western Illinois as the boundary lifted northward. An upper level disturbance initiated the violent thunderstorms, and caused them to move eastward into the Chicago area, producing winds of over 60 mph at the time.  In our area, temperatures were quickly warming into the middle 90's, with moist air moving into the region from the southwest, with dew points eventually approaching the low to middle 70's just before the storms hit the Fort Wayne area. Due to the highly unstable and potent air mass in existence across the area, the storms strengthened rapidly as they left Chicago. At the same time, the storms followed the boundary southeastward into the Fort Wayne. Minutes before the first gust of wind hit the Fort Wayne area, Doppler Radar recorded winds of almost 100 mph at an altitude of 2500 feet above the surface, right before that same patch of winds hit the Downtown area.  It was hard for anyone to prepare for the onslaught that was coming, as the line of storms, called a derecho (De-RAY-sho), were moving at a forward speed of nearly 80 mph! Most storms only move at speeds of 20 to 30 mph. As the storms moved through Fort Wayne, the line once again rapidly intensified in the still highly unstable environment. According to the Storm Prediction Center, a wind gust of 91 mph was recorded at Fort Wayne one of the highest wind speeds ever recorded in the area, while winds of 88 mph just to the northeast of Fort Wayne, producing incredible damage, with widespread tree and structural damage all throughout the city. As the storms strengthened, Doppler Radar also detected strong rotation as the storms passed over New Haven. The National Weather Service then issued a Tornado Warning for East Allen County, Paulding County, and Van Wert County. By the time the storms hit Antwerp, winds of almost 80 mph were reported, according to the Storm Prediction Center (National Weather Service), with even greater damage and widespread tree damage throughout the town. When the storms hit Paulding, a wind gust of 84 mph was recorded near PCH hospital. Even though the storms were extremely violent, they produced minimal rainfall amounts, with most areas seeing a quarter to a third of an inch of rain. Even the highest rainfall amounts were only in the range of 0.4 to 0.5 inches. These storms continued to strengthen as they moved southeast out of the area, knocking out power to almost 700,000 households in the state of Ohio. In fact, the derecho continued all the way to the Mid-Atlantic and out into the ocean, causing considerable damage and widespread communication failures in cities such as Washington D.C. Even though the storms cause more damage in the Eastern states then here, we still recorded the highest wind speeds of the entire event! According to the National Weather Service, this is likely one of the worst storms ever to hit the Northeast Indiana, Northwest Ohio region, and likely one of the worst derecho/squall line events in the Mid-Atlantic and Ohio Valley states ever recorded. At one point, the storms caused a total of more than 3 million power outages at the same time, more power outages than Hurricane Irene produced in the Mid-Atlantic states. From what I have heard on news sites and other places, 22 deaths were attributed to be a direct result of the storm, most of them were from people smashed by trees. This will go down as one of the worst derecho events to the United States, behind the series of derechoes that hit the Upper Midwest in 1995 and '96.

I will be writing an article about the formation of derechoes, and how we can prepare for them, in a couple of weeks.

Historic Heat Wave

     After many, many days of 90 degree temperatures in a row, many records were broken that have not been reached since the years of the Great Dust Bowl back in '34, and '36 (some of the hottest years on record at Fort Wayne). In fact, some all time record high temperatures have been breached several times throughout the heat wave.

     Before I describe all of the records that were broken, I want to give you some background information on why this heat wave formed, and what factors likely exaggerated the effects of an especially historic and legendary heat wave. As most of you probably remember, last winter was a very warm and wet (wet as in a lot of rain) winter. In fact, it came out to be one of our warmest on record, with every month of the winter season, December, January, and February recording temperature surpluses over 6 degrees above normal. While no record highs were set until the meteorological winter season had officially ended, we had quite a few days where temperatures were 20 degrees above normal, especially in February. Usually, during a normal winter season, the area receives a good winter freeze for several weeks, holding the moisture from the late Fall rains and early winter snows. During a warm winter though, evaporation rates are way up because the ground isn't frozen for long enough to hold moisture in. This is why coming into March, our top soils were already quite dry, regardless of the heavy winter rains. Usually, when the strengthening solar radiation hits the normally wet soils of our area, some of heat energy goes to evaporating soil moisture (which ultimately is a cooling process), while the rest goes to raising the temperature of the ground, which conducts into the lower atmosphere, causing a rise in surface temperature. When the ground is relatively dry, less heat energy goes to evaporating water, and more heat energy goes into heating the ground, which effectively raises the temperature of the lower atmosphere much higher and more quickly than a normally wet ground would. This also has an effect of reducing the relative humidity of the atmosphere, which ultimately hinders thunderstorm development. By the time the March “heat wave” hit the area, temperatures were much warmer than they otherwise would be, pushing daily temperatures above normal. Higher temperatures correspond to higher evaporation rates, which deprive the soil of its moisture. At the same time, the synoptic scale wind patterns, driven by the ocean currents and other large scale factors, favored ridging over the area, which means that high pressure is above the area. Higher pressure (pressure rises or more politically correct “height” rises) usually correspond to subsidence in the lower atmosphere (downward motion), and downward motion results in warming by compression, causing a rise in low and mid level temperatures and clear, sunny skies. This further hindered rainfall development during most of April and May. By May, we had two official heat waves (which normally does not occur), with temperatures in the first heat wave reaching the lower 90's, and temperatures during the second heat wave breaking all-time records for two days straight. This is when drought conditions developed across Northeast Indiana, while Northwest Ohio experienced abnormally dry (D0) conditions. With the same synoptic scale patterns that had started during the late winter, the high pressure area or upper level ridge continued to move back into the region after cooler periods of weather. Even in the cooler periods of weather, dryness continued intensifying the drought. By mid-June, a classic heat wave set up across the United States, with records broken in quite a few places. Here, temperatures were in the middle to upper 90's for 4 or 5 days in a row, until the heat broke on June 21 with a violent thunderstorm in some spots. At Fort Wayne International Airport, precipitation for that day was a mere 0.19 inches, while just north and west of Antwerp, Doppler Radar estimated that almost 2 inches of rain fell, right along the state line (my rain gauge recording 0.25 inches of rain from that storm in Antwerp). With continued dry conditions, the next heat wave set up in about a week's time, with the following week reaching well into the 100's, highs officially at Fort Wayne International Airport tied the all-time record high at 106, while Defiance Memorial Airport hit a record of 107 on the same day. During the next several days into July, upper level ridging built back into the area after the incredibly violent storm moved through. The heat wave culimnated by the middle of the week of the Fourth of July, with temperatures 101 and above for each and every day until Sunday. This was an unprecedented event, having four consecutive days above 100 degrees. This has never happened in the history of Fort Wayne with the next closest run of 100 degree temperatures occurring back in July of 1988, with only three consecutive days. With continued heat throughout the rest of the month, I expect that this July will become the hottest July on record, breaking last year's record. (This post will be updated as more information comes in.)

Most of the past heat waves of this year were rather dry with humidity levels not having much influence on the heat index. In the heat wave we had in the last week though, relatively wet soils from the violent thunderstorms and the maturing corn canopy contributed to excessive humidity, with dew points in the low to mid 70's occurring during the hottest part of the heat wave. This contributed to the heat indices that were over 110 at times. Also, favorable flow from the Gulf of Mexico, plus a series of upper level disturbances enhanced moist flow into the region. In theory, this should have produced multiple rounds of thunderstorms to help mitigate (which it did at times) the heat, but so far it has failed to do this because of a lack of strong lifting mechanisms, and strong capping (warm mid level temperatures) has thus far prevented widespread thunderstorm activity.

This heat wave's effects have also been exaggerated by the fact that the powerful derecho that slammed into the region, caused millions of power outages from Indiana to Washington, D.C. As of this writing (Friday, July 6, 2012), nearly 1.5 million are still without power in the areas affected by this storm in Ohio, West Virginia, and Virginia. Many people are without air conditioning during one of the worst heat waves in many years.

For what I think will happen in the long run, given no significant rainfall in the near future, drought conditions will continue, contributing to above normal temperatures, and exacerbating heat waves that plague the area. This will likely continue into August and even September before the changing climatic variables and ENSO phases within the Pacific affect the long-range patterns.

Extended Heat Wave Possible.

Even as the post-clean up process from Friday's storms is underway, another heat wave is on the horizon. Except this one will last an entire week. In fact, the National Weather Service has issued an Excessive Heat Warning for the area. The National Weather Service said that they are expecting a period of heat which will feature temperatures in the upper 90's to the lower 100's and heat indices well above that. This heat wave will be characterized by high humidity and maximum sunshine, which only make it worse for the many thousands of people who still need power. Even the heat does not exactly fit criteria for the excessive heat warning, it was issued because of its duration and impact. This heat wave is caused by a building heat dome or upper level ridge moving in from the west. This will allow for several days of quiet weather. By next weekend though, temperatures will reach their maximum on Saturday, near or over 100. Then a cold front will be forced through the area, cooling temperatures back into the lower 90's and upper 80's.