June 2015

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Latest Monthly Assessment - Abnormal warmth and dryness across the Northwest and much of the eastern third of the U.S. contrasted with widespread above normal precipitation and cooler weather across the southern Rockies, Plains, and upper Midwest. Drought has been almost entirely removed from the central and southern Plains, but repeated bouts of heavy rainfall and severe weather resulted in widespread devastating flooding. Drought conditions intensified across the Northeast, while abnormal dryness expanded across the southern Appalachians and parts of the Southeast. Short term dryness and drought conditions also expanded across parts of the Northwest. During June, seasonably dry weather across the western third of the U.S. coupled with extremely low mountain snowpack levels will promote drought persistence and intensification. Additionally, monthly forecasts favoring continued dry, unseasonably warm weather across the Northwest will promote additional expansion of drought across Washington and Oregon. Across the Nation's midsection, forecasts favoring a continued pattern of near to above normal precipitation will lead to further drought reductions, possibly ending drought conditions completely across most of the Plains. Across the East, a frontal boundary early in the period is forecast to bring widespread rainfall, easing moderate drought and abnormal dryness across the Southeast and interior New England. Monthly outlooks favor continued above-median precipitation across the Southeast, which will help to prevent additional drought development. A potential for continued unseasonably warm weather across the Northeast will promote drought persistence across southern New England despite potentially heavy rainfall to start the month. Seasonably dry weather across Hawaii favors drought persistence despite a wet climate signal associated with El Niño. Drought persistence and development is possible across eastern Puerto Rico, as El Niño summers typically dry out over the Caribbean. Across Alaska, dry May weather and early snowmelt may promote Summer drought development, although current favorable moisture conditions lessen the potential for any development during June.

Tools used in the U.S. Monthly Drought Outlook (MDO) included the official Climate Prediction Center (CPC) updated temperature and precipitation outlooks for June 2015, various short- and medium-range forecasts and models such as the 7-day precipitation totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC forecasts, week 3 and 4 experimental outlooks, the NAEFS precipitation outlooks, dynamical models (CFSv2), the 384-hour total precipitation forecasts from several runs of the GFS, climatology, the latest official Drought Monitor analysis (released on May 28), observed precipitation during the previous month, and initial conditions.

Thunderstorms across southern Florida have been largely isolated during mid-May; however, rainfall accumulations are likely to increase as the rainy season begins in earnest. More widespread thunderstorm activity is anticipated during early June, with the CPC 6-10 and 8-14 day outlooks indicting enhanced chances for above-median precipitation. The revised CPC monthly outlook indicates equal chances for below, near, or above-median precipitation. Based on climatology and the shorter range forecasts, drought removal is likely.
Forecast confidence for southern Florida is high.

Across the remainder of the Southeast and east-central U.S., dry, warm conditions promoted expansion of abnormal dryness (D0) across parts of Mississippi, Alabama, and Georgia, with a small area of moderate drought (D1) developing over southern Georgia. Additionally, widespread short term D0 was introduced across much of the southern Appalachians and eastern Tennessee Valley on the May 26, 2015 U.S. Drought Monitor. In the short term, heavy precipitation (1 to locally 5 inches) is anticipated along a frontal boundary extending from the eastern Tennessee Valley though the southern and central Appalachians. Widespread rainfall exceeding an inch is forecast across the rest of the Southeast. This rainfall will help alleviate the developing dry conditions, and may delay or halt additional drought development. The CPC 8-14 day outlook maintains a wet pattern across the Ohio Valley and Southeast, while the revised monthly outlook indicates enhanced chances for above-median rainfall across the Gulf Coast States. Given these outlooks, additional drought development across the east-central U.S. seems unlikely, and removal of drought over southern Georgia is anticipated during June. Given the dry incipient conditions, however, any extended period of dry, hot weather could promote rapid short term drought development during the Summer.
Forecast confidence for the Southeast and east-central U.S. is moderate.

Below normal precipitation and unseasonably warm weather during the past two weeks continued to promote drought degradation and expansion across the Northeast. As of May 29. record low 7-day streamflow values were common from the mid-Atlantic states through southern New England, and spotty showers and thunderstorms did little to boost soil moisture. Irrigation needs are increasing to maintain good crop conditions. Current agricultural impacts remain relatively low given the dry conditions, primarily due to cool Spring weather that slowed snow melt and evapotranspiration rates. Due to the dry Spring, conditions have the potential to deteriorate rapidly during any episodes of Summer heat and dryness, with a climatology that favors soil moisture loss. During the next several days, however, widespread heavy rainfall along and north of a slow moving frontal boundary is expected to boost topsoil moisture and streamflows, with the heaviest accumulations (2 to 5 inches) over interior New England. Accumulations of 1 to 3 inches are forecast across coastal areas of southern New England. These rains will likely ease moderate drought and abnormal dryness across parts of New York, Hew Hampshire, far western Massachusetts, Vermont, and Maine. Due to the large incipient precipitation deficits, however, the rains may not be sufficient to substantially improve drought conditions across southern New England. A period of dry weather is anticipated in the wake of these early June rains. Longer range forecasts are mixed, with high spread among dynamical model ensemble members. The CPC 8-14 day outlook slightly favors above-median precipitation based on the ECMWF, while the CFS model persists abnormal dryness into Weeks 3 and 4. Forecasts at all time scales favor above-median temperatures, which will promote high evapotranspiration rates. This could make any improvements from the near term heavy rainfall short lived in the absence of significant additional Summer rainfall.
Forecast confidence for the Northeast is low.

An extremely active pattern, partly associated with El Niño related climate anomalies, continued across the central and south-central U.S., promoting widespread heavy rainfall. These rains continued to erase drought conditions that have persisted for 3 years, but also led to devastating and deadly flooding across parts of Texas and Oklahoma. Currently, only small areas of long term (multi-year) D1 remain across the Plains. Significant rainfall also fell across the upper Midwest, promoting drought reduction across Minnesota and Wisconsin. Additional widespread rainfall fell across the south-central U.S. following the latest Drought Monitor period, exacerbating flooding and adding to massive runoff that is currently filling reservoirs. These rains may further reduce the remaining drought areas across the central and southern Plains. During the next several days, drier weather is forecast across much of Kansas and Oklahoma, but widespread rainfall is anticipated to return to much of Texas, the northern Plains, and the upper Midwest. Both the CPC 8-14 day outlook and the revised monthly outlook maintain a wet signal across most of the Plains and Midwest. Based on current conditions and these outlooks, continued drought reduction is expected, and the Plains may be largely drought-free during much of June.
Forecast confidence for the Plains and upper-Midwest is high.

Widespread long term drought conditions continue across the western third of the Nation. Heavy precipitation and late season snowfall brought improvements to parts of the central and southern Rockies, while dry, unseasonably warm weather promoted additional short term drought development across the Northwest. A generally dry June climatology across the western U.S. makes drought improvement unlikely, while extremely low mountain snow water content across the northern Rockies, Sierras, and Cascades will limit any early summer reservoir recharge. Monsoon rainfall generally increases later in the summer, making further improvements across New Mexico and southwestern Colorado unlikely. Based primarily on climatology and the lack of snow cover, drought persistence and intensification are expected across most of the West during June. Additionally, CPC 6-10, 8-14, and the revised June outlook all favor a continuation of hot, dry weather across the Northwest. These conditions are anticipated to promote additional drought expansion across northwestern Washington and western Oregon. A wetter climatology makes drought development across northern Montana less likely than areas further west.
Forecast confidence for the western third of the Nation is high.

Localized heavy thunderstorms eased abnormally dry conditions near San Juan, Puerto Rico, while rainfall deficits continued to increase across other eastern areas of the island. Interior western portions of Puerto Rico have received more generous rainfall during the past month. A dry signal becomes increasingly apparent during typical El Niño summers across the Caribbean, with the dryness more prominent during August and September, as vertical shear inhibits organized tropical convection. Dynamical models, including the GFS, CFS and ECMWF favor near to above-normal precipitation across the northern Caribbean during the next several days, with a return to near normal or slightly below normal precipitation thereafter. Experimental Weeks 3 and 4 forecasts from the CFS coupled model favor increasingly dry conditions, consistent with the low frequency ENSO state. Based on ENSO climatology and initial conditions, drought persistence is anticipated, with development possible in current D0 areas that have missed out on recent rainfall.
Forecast confidence for Puerto Rico is moderate.

Despite El Niño climate anomalies favoring wetness across Hawaii, persistence of existing drought areas is anticipated, as it is a relatively dry time of year.
Forecast confidence for Hawaii is moderate.

Abnormal warmth promoted rapid snowmelt across south-central Alaska. Below normal precipitation was also observed during much of May, and D0 conditions have expanded as a result. The revised CPC June outlook indicates enhanced chances for above median precipitation across southern Alaska, with a dry signal favored over the north-central interior. Enhanced chances for above-median temperatures are also anticipated, which increases the possibility for Summer drought development extant D0 areas, however, wetness during April may slow the emergence of drought impacts, making June development specifically less likely.
Forecast confidence for Alaska is low to moderate.