Latest Seasonal Assessment -
During the past three weeks (since May 16), an active weather pattern, consisting of a series of slow-moving storm systems tracking across the northern tier of the
Nation, brought ample rainfall to the Pacific Northwest, the northern thirds of the Rockies and High Plains, much of the Great Plains, Midwest, Delta, Great Lakes
Region, New England, and southern half of Florida. 3-week temperatures have averaged below normal in the Northwest , northern Rockies and Plains, and upper Midwest. Since
May 1, the heaviest rains (more than 7 inches) have fallen on parts of the northern High Plains, the middle Mississippi Valley, central Great Plains, the upper and
lower Delta, parts of Florida, and the southern Appalachians. In contrast, drier conditions were observed in the Southwest, the southern Rockies and High Plains, portions
of the Southeast, especially Alabama, the eastern Ohio Valley, and the mid-Atlantic.
Meanwhile, ENSO-neutral conditions persisted across the tropical Atlantic, with most models forecasting no major changes to conditions into Fall 2013. In addition, the
2013 Caribbean and Atlantic hurricane outlook (released May 23) called for an active, above-normal season. There was a 70 percent likelihood of 13-20 named storms, of
which 7-11 could become hurricanes, including 3-6 major hurricanes. The normal season averages 12 named storms, 6 hurricanes, and 3 major hurricanes. This does not imply,
however, that the storms will make landfall, but an active tropical season would increase odds that some of the storms will impact land.
Year-to-date (YTD) precipitation (to June 4) has been subnormal in much of the West, southern Plains, central High Plains, parts of Florida, eastern North Carolina, and
most of the northeastern quarter of the Nation. Coincidentally, the precipitation pattern since April 1 is similar to the YTD percentages, except for wetter conditions in
the Northwest , Texas, northern New England, and Florida. The greatest YTD deficits (more than 8 inches) were limited to the Far West along the Washington, Oregon, and
California coasts, and in the Cascade and Sierra Nevada Mountains. Deficiencies since January 1 exceeding 4 inches were found from the eastern Ohio Valley into coastal New
England, coastal North Carolina, west-central Florida, and parts of Texas, western Oklahoma, and southwestern Kansas. In contrast, surplus precipitation has fallen on the
northern thirds of the Rockies and Plains and upper Midwest southward to the central Gulf Coast, in most of the Southeast, and the southern Appalachians. In a sharp
contrast to last year at this time, YTD temperatures have averaged below normal across most of the lower 48 States, especially in the northern Plains and upper
Midwest (-4 to -8 degF), with slightly above normal readings limited to New England, California, and parts of Texas and Florida.
Accordingly, drought expansion occurred over the past 3 weeks in the West and Southwest. Abnormal dryness and drought briefly expanded in parts of the Northwest and
Northeast 2 weeks ago, but recent rains have pared back much of the increase. In contrast, improvements were made along the northeastern and eastern edges of the main
drought area in the Nation’s midsection, in the Southeast, and parts of the Northeast. The worst conditions (D3 to D4) have stubbornly persisted in the southern and
central High Plains, although this area just recently received welcome rains (1-3 inches).
The updated June temperature and precipitation outlooks (released May 31) favored below median rainfall in the Northwest and southern and central High Plains, above median
precipitation odds in the eastern Gulf and southern Atlantic Coasts and southeastern Alaska, and equal chances elsewhere. A tilt toward above-median June temperatures were
forecast for most of the western third of the U.S., with the best chances for above median readings in the Great Basin and Oregon. Some of the dynamical models hinted at
cool and wet June in the eastern half of the Nation, but they were not consistent and skillful enough to be included in the monthly outlooks.
The seasonal temperature and precipitation outlooks (released May 16 with no update) are somewhat similar to the updated monthly outlooks, with odds for below median
rainfall in the Northwest and southern and central High Plains. A small area of above median rainfall was drawn along the central Gulf Coast and in southeastern
Alaska. Above median temperatures are also favored for most of the West, with the highest odds in the southern halves of the Rockies and High Plains. In addition, the
chances for above median warmth extended eastward along the Atlantic Coast, with slightly higher probabilities centered over the Northeast. For the southwestern summer
monsoon, a slight tilt toward below median rains was indicated in eastern areas (e.g. New Mexico and west Texas).
Although CPC odds favored subnormal June and JJA rainfall, spring rains continued into late May across most of Hawaii, eliminating drought on Kauai, Oahu, and most of
Molokai. But with the normal wet season tapering off and the southern islands observing subnormal March and April rains, persistence remained on the leeward sides of Maui
and the Big Island, with development possible on their windward sides. In Alaska, the Koyukuk Basin of north-central Alaska was left as some improvement with no tilt in
odds either way (e.g. equal chances) for June and JJA precipitation.
Tools used in the U.S. Drought Outlook (USDO) included the official updated CPC temperature and precipitation outlooks for June 2013 (released May 31), the long lead
forecast for June to August 2013 (released May 16), various short- and medium-range forecasts and models such as the 5-day HPC precipitation totals, 6-10 day and 8-14
day forecasts, the NAEFS precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil (CAS) moisture,
dynamical models (CFSv2, NMME, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the four-month Palmer drought termination and
amelioration probabilities, climatology, and initial conditions.
We are currently in ENSO Neutral conditions as of this forecast release date, and are forecast to remain this way into late 2013. The 2013 Caribbean and Atlantic
hurricane outlook released May 23 called for an active, above-normal season. There was a 70 percent likelihood of 13-20 named storms (average=12), of which 7-11 could
become hurricanes (average=6), including 3-6 major hurricanes (average=3). This does not imply that any of the storms will make landfall, but an active tropical
season would increase odds that some of the storms will impact land.
During the previous three weeks, moderate to heavy rain (5 to 8 inches, locally to 12 inches) fell on southern and central Florida, and from the southern Appalachians
and North Carolina northward into New England. The rains halted, and in some cases, reversed a drying trend that had seen an increase in D0 and D1 in New England and
Florida in mid-May. In contrast, minimal rains have fallen on parts of the South, especially Alabama and the Florida Panhandle, as D0 has increased there. During the
next week, a disturbance in the central Gulf of Mexico is expected to track northeastward, bringing moderate to heavy rains to most of Florida and much of the
Atlantic Seaboard. The 6-10 and 8-14 day outlooks also have good odds for above median rainfall for the Northeast. The monthly and seasonal precipitation outlooks
have above median odds for Florida (updated June) and the central Gulf Coast (initial JJA), with some of the latest runs of the CFSv2 climate models indicating
positive precipitation anomalies for the southeastern U.S. for June. With the wet short-term forecasts for Florida and the East Coast, a trend toward wetness in the
Southeast since February, a forecasted active 2013 Atlantic and Caribbean hurricane season, and the peak summer rainy season for Florida, the small pockets of drought
along the Gulf and East Coasts are likely to vanish by the end of August.
Forecast confidence for the Gulf and Atlantic Coasts (Alabama-Florida to New England) is moderate to high.
Ample moisture during 2013, along with subnormal year-to-date (YTD) temperatures (departures as large as -4 to -8 degF in ND and MN), have not only recharged the top
and subsoil moisture levels, but has led to flooding and saturated soils in parts of the upper and middle Mississippi Valleys. During the past three weeks, surplus
precipitation (more than 5 inches) fell from eastern parts of South Dakota, Nebraska, and Kansas eastward to Michigan, Indiana, and Kentucky. Lesser totals fell on
parts of southwestern and northern Minnesota, hence the remaining drought there. Light to moderate rains are expected across the upper Midwest and Ohio Valley during
the next 5 to 7-days, with changing odds for below, and then above median precipitation during days 6-10 and week 2, respectively, in the upper Midwest. The CPC June
and JJA precipitation outlooks have equal chances in the Midwest. Based on a persistently wet trend this year, along with short and medium-term guidance of surplus
precipitation, further improvement is expected.
Forecast confidence for the Midwest is moderate to high.
The northern Plains (eastern Montana and North Dakota) received above normal precipitation late in 2012, subnormal amounts during January-April, then heavy rains
(over 6 inches) during the past few weeks, causing saturated soils and localized flooding. The surplus rains have also recently fallen on South Dakota, Nebraska, and
eastern Kansas where late 2012 was very dry, but mostly above normal precipitation has fallen this year, along with subnormal temperatures. Climatologically, the
northern and central Plains precipitation rapidly increases in the early spring (April) and peaks in the early to mid-summer before rapidly decreasing by the fall. As
a result, this is a critical time for the Plains to receive significant amounts in order to diminish the large deficits (5 to 15 inches) accumulated last year.
Fortunately this year, most northern Plains locations have been receiving large totals. The HPC 5 and 7-day precipitation forecasts call for light to moderate rains
in the northern third of the Plains and upper Midwest. The CPC week 2 outlook tilts the odds towards above median precipitation across the northern Plains (equal
chances at 6-10 days). The CPC updated June and initial JJA outlooks generally forecast equal chances of precipitation and temperatures for the northern Plains, but
gradually increase the odds of below median precipitation and above median temperatures the farther south one goes. Based on the favorable odds of above normal
precipitation in the short and medium term, a normally wet summer climatology, and the recent trend of wet and cool weather, improvement to some improvement is
expected in the northern half of the Plains, especially along the northeastern and eastern edges of the main drought area. However, reducing any summer drought
improvements are the normally high summer temperatures, wind evaporation, and plant evapotranspiration.
Forecast confidence for the northern half of the Plains is moderate.
During the first five months of 2013, surplus precipitation and subnormal temperatures have brought drought improvement or alleviation to parts of eastern Kansas,
eastern Oklahoma, and northeastern Texas. Just to the west, however, much drier weather this year has maintained or worsened D3 and D4 conditions in western sections
of Texas, Oklahoma, and Kansas, and southeastern Colorado. However, June provided a nice change of pace as beneficial rains (1 to 3 inches) finally fell on
southeastern Colorado, western Kansas, and the Oklahoma Panhandle the past 2 days. Similar to the climatology of the northern Plains, the southern Plains also
receives the bulk of their annual precipitation during the summer months, although the rains normally start later and linger into the early fall months (e.g. New
Mexico’s wettest 3-months are JAS). This starts a crucial period for badly-needed rains in the southern Plains and the Southwest summer monsoon. Unfortunately, most
of the short, medium, and long-term forecasts are not favorable for drought improvement, especially in western sections. Light to moderate rains are forecast for
eastern portions (Great Plains) of Texas, Oklahoma, and Kansas during the next 5 to 7-days, but little or no rains are expected in the southern and central High
Plains. An exception is a small band of 1 inch rainfall in the HPC 5-day forecast for northeastern New Mexico into west Texas, and in southwest Texas. Unfortunately,
the CPC 6-10 and 8-14 day outlooks tilt the odds in favor of below median precipitation and above median temperatures, while the CPC June and JJA outlooks both
indicate enhanced chances of below median precipitation and above median temperatures for the southern High Plains. Accordingly, even with recent rains and the
somewhat promising 5-day HPC forecast, all other indicators and tools pointed toward below median precipitation and above median temperatures at all time periods,
particularly in western regions. Therefore, drought is expected to persist or develop in the few areas not yet in drought. The exception to this is improvement or
some improvement in far eastern sections of Texas, Oklahoma, and Kansas where favorable 2013 weather has already brought some drought relief.
Forecast confidence for the southern half of the Plains is moderate.
In the West, after a great start to the 2012-13 Water Year (a very wet November and December), near-record and record dryness enveloped the region during
January-April. May was a mixed bag, with above normal rains (albeit with low normals) in the extreme northern and southern sections and parts of the Sierra Nevada,
and mostly dry elsewhere. As a result, the memory of the wet start to the Water Year faded away, gradually replaced by impacts from the 2013 dryness. In addition,
the start of the normally dry summer and fall months has commenced (along with an early fire season), making it highly unlikely that any substantial precipitation
will occur during the next several months. An exception is the Pacific Northwest where occasional Pacific storms dampen the region – as they did during the past 2-3
weeks, temporarily halting the northward advance of D0 and D1. Not surprisingly, the HPC 5-day, CPC 6-10 and 8-14 day, June and JJA outlooks all predict equal
chances (arid climatology) or enhanced chances of below median precipitation for California and the Southwest. For the southwest summer monsoon, the tools were not
in full consensus in western areas (e.g. southeastern California, Arizona, southern Nevada, Utah), hence equal chances. In the eastern areas (e.g. New Mexico, west
Texas, southeastern Colorado), however, the CPC June and JJA outlooks both indicate enhanced chances of below median precipitation and above median temperatures for
the southern High Plains. Based on ongoing impacts from the record dry January-April, normally dry summer climatology, and monthly and seasonal outlooks, drought
persistence is expected in much of the West, with development possible in the Northwest (e.g. Oregon, Idaho, western Wyoming, southwestern Montana). Development was
limited to current areas categorized as D0 (abnormally dry) in the most recent U.S. Drought Monitor.
Forecast confidence for the West is high, moderate in the Southwest.
An increase in the intensity and coverage of April showers across Kauai, Oahu, and Molokai that lingered into late May brought improvement of drought conditions.
Drought was erased from Kauai, Oahu, and most of Molokai, while unseasonably heavy May rains also diminished the drought on Lanai, Maui, and the Big Island.
However, with the CPC June and JJA outlooks for Hawaii both tilting the odds toward below median precipitation and the rainy season at an end, the drought outlook
was fairly straightforward. Accordingly, persistence is forecast for the leeward sides of the central and southern islands, with development on the windward sides
where D0 is currently depicted on the latest U.S. Drought Monitor.
Forecast confidence for Hawaii is moderate to high.
Low snowpack and snow water content (about 75 percent of normal on May 1) for the Koyukuk Basin of north-central Alaska maintained D1 conditions as of the June 4 U.S.
Drought Monitor. The CPC 6-10 day and 2 week precipitation outlooks are both near normal for this area, with odds tilting for above median precipitation to the north
and below median precipitation to the south. June and JJA outlooks also have no tilt for precipitation (equal chances) here, but the basin may benefit from late
spring snowfall and the resulting summer melt. In addition, the summer months are normally the wettest time of the year in north-central Alaska, so the climatology is
favorable for producing decent rain totals. Therefore, some improvement may be expected by the end of August.
Forecast confidence for Alaska is moderate.