When thinking about drought and heat waves, it is natural to focus on the western contiguous United States or other parts of the world where dryness is a more conspicuous and frequent fixture of the climate. Many parts of the South Central and Western United States are currently experiencing serious drought conditions, with nearly 100% of the land area of California, Nevada, Utah, and Oklahoma in drought and over 10% of California, Texas, and Kansas classified as being in “Exceptional Drought,” the most extreme category. The dryness across this region has also played a role in the heatwaves that have been experienced over the summer. While much of the drought community’s focus is currently on events in the central and western U.S. There is also an ongoing drought event in the Northeast United States.
An important part of NOAA’s mission is improving our understanding of the nature of extreme conditions across the country to better anticipate, react to and manage their effects on communities. To achieve this goal, the MAPP and NIDIS programs are funding work to understand the nature of drought and developing tools for better preparedness.
One of such studies is focused on understanding the connection between drought and heatwaves in the Northeast US. This study is being carried out by Profs. Mathew Barlow and Christopher Skinner at the University of Massachusetts Lowell. The study aims to identify the drivers that are most important for rainfall and droughts in the Northeast and examine whether climate change may alter the relative importance of those drivers.
Despite its typically temperate moist climate, the Northeast US frequently experiences short-term intense dry periods that can follow a period of normal to above-normal precipitation. Even with normal to above normal precipitation since the 1980s, the region is currently in an economically impactful drought. Starting with reduced snowfall this past winter and progressive drying of soil moisture since May, there has been an increase in evaporative demand, or atmospheric thirst for soil moisture in the region. The U.S. Drought Monitor in May revealed that increased rainfall deficits, reduced soil moisture, and lower-than-normal streamflow and groundwater levels caused the onset of moderate droughts and unusually dry conditions in many areas of the Northeast, leading to several New England brushfires. Despite a series of severe storms that brought precipitation to parts of the region, June was drier than usual, with drought and extreme dryness prevailing, especially in New England, and a hot, mostly dry July allowed the drought to intensify. The high evaporative demand, along with a lack of rainfall played a role in the strengthening of the drought.
From May through June, daily weather in the Northeast transitioned to favoring more dry circulation patterns, and in July, narrowed further to dry and hot patterns, forcing drought with both precipitation deficits and evaporative demand. Understanding how droughts and heatwaves evolve and interact is important to improving both short-term weather predictions and longer-term climate projections.
Recent drought monitoring reveals there was little improvement and mostly deterioration of drought conditions across the Northeast. Drought extends throughout New England with severe drought hitting communities in eastern Massachusetts. Areas of New York, Pennsylvania, and New Jersey are also facing abnormal dryness. The reduction in precipitation and consequently, the amount of available water, is one of the leading contributors to the dryness in the region. Conversely, a few portions of the other northeastern states have had some heavy rainfall that has led to the alleviation of drought. More information on the current state of drought conditions in the Northeast can be found here.
A look at the mid-range forecast shows that conditions are likely to continue to be drier and warmer than normal through the next couple weeks, while the longer-range seasonal forecast also anticipates persistence in the Northeast drought.
The researchers on the Northeast project have begun developing a methodology for tracking key heat wave and drought patterns for long-range forecasts in the Northeast. The study has been able to determine the primary sources of precipitation and drought in the region. Their analysis identified several circulation patterns that are more frequent during drought periods and they are currently investigating the relative contributions of these patterns to the lack of precipitation during droughts.