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U.S. Drought Monitor Report for the Week Ending Sept. 17 (Text)

Following is the text of the weekly U.S. Drought Monitor as released by the National Drought Mitigation Center in Lincoln, Nebraska:


Weather Summary: The combination of ample Gulf and Pacific
tropical moisture (in part from Tropical Storms Manuel (Pacific)
and Ingrid (Gulf) which inundated Mexico), stalled frontal
systems, and upsloping conditions produced widespread heavy to
copious rainfall (widespread 2 to 6 inches, locally 12 to 18
inches especially near Boulder, CO) and severe flash flooding in
parts of New Mexico and Colorado. Moderate to heavy rains (1.5
to 4 inches) also drenched portions of Arizona, eastern Nevada,
Utah, Wyoming, south-central Montana, western sections of
Nebraska, Kansas, Oklahoma, and northern and southern Texas.
September monsoonal rains have generated welcome relief from the
drought in the Southwest, central Rockies, and High Plains, but
unfortunately have been accompanied by flash flooding.
Elsewhere, a pair of cold fronts during the week brought relief
from last week’s unseasonable heat in the Midwest and Northeast,
along with light to moderate rain that generally prevented
further deterioration of conditions. Hit and miss (mostly miss)
showers occurred in the Southeast, with the most significant
rains (more than 2 inches) limited to southern Florida. Warm and
mostly dry weather returned to the Northwest after a wet first
week of September. Wet weather continued across most of Alaska,
while decent windward showers returned to the Hawaiian Islands.

The Northeast:  The passage of two cold fronts brought both rain
and heat relief to New England and the mid-Atlantic. The rains
were more widespread and heavier in New England (2 to 5 inches),
but unfortunately less so to the south. Although 0.5 to 1.5
inches fell across the D0 areas in Pennsylvania, Long Island,
and the mid-Atlantic, short-term deficits (at 60- and 90-days)
continued to accumulate. As a result, a slight expansion of the
abnormal dryness was made by linking the two areas in central
Pennsylvania and Maryland together where 50-75% of normal
precipitation has fallen the past 60 and 90 days, creating
shortages of 2 to 4 inches. Fortunately, a wet spring and early
summer plus cooler weather has tempered the potential negative
impacts of the recent dryness. Most USGS 14- and 28-days average
stream flow values in the region are near normal, although some
sites in the D0 areas are below the 25th percentile, and a few
in Maryland are below the 10th percentile.

The Midwest: After several weeks of rapid deterioration due to
“flash drought” conditions in the Midwest (lack of rain + heat),
this week finally brought some relief with lower temperatures
and light to moderate rain via two separate cold fronts. Locally
heavy rains (1.5 to 3 inches) that fell across west-central
Minnesota was enough to remove the D0 there, and 2-weeks of
moderate rains in west-central Illinois reduced shortages enough
to improve to D0.  The widespread 0.5 to 1 inches of rain that
occurred elsewhere was enough to prevent further deterioration,
but not enough to significantly dent the 90-day accumulated
deficits. In contrast, rainfall amounts diminished across
southern sections of the Midwest, with weekly totals under 0.5
inches. With increasing deficits at 60- and 90-days, abnormal
dryness was expanded across most of Indiana, southwestern Ohio,
and southern Illinois. D1 similarly increased near St. Louis, MO
area, central Illinois, and central Indiana. 60- and 90-day
deficiencies have reached 3-6 and 4-8 inches, respectively, in
the aforementioned D1 areas. Historically, after a relatively
wet June (and spring), the summer months (Jun-Aug) were ranked
as the 13th, 32nd, and 36th driest since 1895 (119 years) for
Iowa, Minnesota, and Illinois, respectively, according to NCDC,
depicting how dry July and August were. Fortunately, summer
temperatures averaged below normal. Agriculturally, the recent
heat (and Jul-Aug dryness) created declines in potential crop
yields while it accelerated the denting and maturity stages of
corn to values well above the 5-year averages. Corn and soybean
crop conditions rated good to excellent fell from early July
highs of 68 and 67% to 56 and 54% by September 1, respectively,
according to NASS/USDA.

The Lower Mississippi Valley:  Since late July, much of the
lower Delta region (Louisiana, southern Arkansas, western
Mississippi) has missed out on significant rainfall that has
fallen on nearby areas. This week was no exception as Louisiana
averaged only 0.24 inches this past week with a departure from
normal of -0.85 inches. Many locations received no rainfall, and
temperatures averaged 2 to 4 degrees F above normal.
Precipitation has been under 25% of normal the past 30 days, and
between 50-75% of normal during the past 60- and 90-days, with
shortages of 3-6 and 4-8 inches, respectively. The drier weather
has started to creep eastward, with western portions of Alabama
now below normal at 30- and 60-days. The USGS 1-, 7-, 14-, and
28-day stream flows have dropped below the tenth percentile in
central parts of Louisiana and Mississippi. The summer months
were also quite dry in Louisiana, with a ranking of 22nd driest
summer (June-August) since 1895, according to NCDC. Accordingly,
D0 through D3 was expanded eastward to cover the driest areas
during the past 2 to 3 months.

Northern and Central Great Plains: The Dakotas observed opposite
conditions as decent rains (2-4 inches) the past two weeks fell
on most of North Dakota, easing drought conditions along the
western edge and southeastern section as 60-day deficits were
reduced while 90-day surpluses were found. In contrast, most of
South Dakota was dry, with only half an inch of rain measured in
the extreme northeastern part of the state. Although near to
surplus rains have fallen across western and southern South
Dakota the past 60-days, the northeastern corner has measured
less than 25% of normal precipitation. For example, Aberdeen
(1.02”), Webster (1.20”), Clear Lake (1.12”), Watertown (0.96”),
and Bryant (1.62”) totals since August 1 are at near-record dry
levels. This dryness, plus the recent heat that caused loss of
potential crop yields (especially soybeans) justified a return
of D2 in this area. In Nebraska, rains were limited to the
southern half and far western portions of the state. Weekly
totals generally ranged around an inch, keeping conditions
status-quo. An exception was along the Kansas border and in the
extreme southwestern and far western areas where amounts
exceeded 2 inches, allowing for some slight drought reductions
to be made. In Kansas, heavy rains (more than 2 inches) fell
across the northern half of the state, with up to 7 inches
falling in the northwestern corner, while decent rains also
occurred in western and southern sections. As a result, D4 was
eliminated from Kansas (to D3) while a reduction in the eastern
D0-D3 edges were made. The D0 edge in eastern and southern
Kansas was also pared back. Some small 2-category improvements
were done in northwestern Kansas in association with the
heaviest rains.

Southern Great Plains:  In Oklahoma and Texas, general
improvements were made in western sections while eastern
portions deteriorated. In the Oklahoma Panhandle, copious
monsoonal rains that inundated parts of the Southwest and
central Rockies and caused flash flooding also soaked the
extreme western Panhandle (and southeastern Colorado) with over
5 inches of rain, enough for a 2-category improvement to D1.
With lesser totals (1.5 to 3 inches) just to the east, a 1-
category improvement was made to the rest of the Oklahoma
Panhandle and in northwestern Oklahoma. Similarly, 2 to 4 inches
of rain along the KS-OK border was enough to erase D0 in Kay and
Osage counties. However, little or no rain along the Red River
Valley continued the dry trend in southern sections of the state
as D2 and D3 expanded in extreme southern Oklahoma and across
much of eastern Texas (and Louisiana). 30-day rainfall was under
25%, while 60- and 90-day precipitation hovered around 50%,
creating 3-6 and 4-8 inch deficits, respectively. In contrast,
tropical moisture from Tropical Storm Ingrid in the western Gulf
pushed enough moisture northward to dump 2 to 7 inches of rain
on southern Texas. Frequent tropical showers have brought
Brownsville, TX, 11.29 inches of rain so far this month, with
Harlingen at 8.14 inches and McAllen at 5.99 inches.
Accordingly, drought was reduced a category where the heaviest
rains fell.

The Southwest: The robust southwestern summer monsoon exploded
with copious rainfall (6 to 12 inches, locally over 18 inches
near Boulder, CO) across portions of New Mexico and Colorado,
producing severe flash flooding, loss of lives, and the
destruction of property and infrastructure. The combination of
ample Gulf and Pacific tropical moisture (in part from Tropical
Storms Manuel (Pacific) and Ingrid (Gulf) which inundated
Mexico), stalled frontal systems, and upsloping conditions
produced the widespread rainfall. Other states in the
surrounding region (Arizona, Nevada, Utah, southern Idaho,
Wyoming, south-central Montana) and the High Plains also
received beneficial moisture from the monsoon, not only this
week but in weeks past. In Colorado, widespread flooding was
realized from these rains on the Cache la Poudre, South Platte,
Big Thompson, and St. Vrain Rivers where communities were
stranded as roads collapsed. This was a historic flood
(estimates are currently a 100 year flood) for the Front Range,
and as such, many improvements are warranted. In some cases, 2-3
category improvements were recommended as 3 inches of rain is
approximately 20% of the normal ANNUAL total at many locations.
This event was not convective activity, but more tropical in
nature, falling for several days in succession. This time of the
year is also a huge consideration for improvement as it allows
for excellent soil moisture storage going into the fall when
evapotranspiration rates are much less as compared to the height
of the growing season. In New Mexico, similar 4-10 inch totals
(minus the excessive 18 inches) fell, also leading to a
widespread 1-category improvement statewide, but due to the
prolonged 3-year drought, 2-category improvements were very
limited. It will be interesting to see how quickly and how much
the major reservoirs in New Mexico react to these rains.
Similar 1-category improvements were made in Arizona, Utah,
Wyoming, and south-central Montana where 2-4 inches of rain
diminished long-term deficits. Numerous flood warnings were
issued by the NWS in these states, and with no surprise, most
USGS stream flow levels were currently at near or record high
flows.  Although Arizona saw less rain this week, last week’s
downpours were enough to increase flows on the Gila River that
raised water levels at the Coolidge Dam by 7 feet, with a few
more feet still expected.

The West: The heavy monsoonal rains that inundated the Southwest
and central Rockies bypassed the West, leaving warm and dry
weather instead. As this is the normally dry summer and early
fall season, no changes were made to much of the region. An
exception was made in extreme southern California where isolated
heavy showers (1 to 2.5 inches) fell west of the Salton Sea last
week, and that was enough to reduce Water Year-To-Date (WYTD)
deficits and change D2 to D1. Similarly in eastern Nevada,
additional showers (1 to 2.5 inches) continued to diminish the
long-term deficits in the region, allowing for some minor
improvements to D2 and D3 areas.   In contrast, along the coast
near San Diego, CA, D2 was expanded as the WYTD percentages were
similar to areas just to the north (between 25-50%).  In
California, the 154 reservoirs are at 79% of average; last year
at this time it was 90%. The reservoirs are not at critical
levels yet as they need to be in the 30-40% range to be
critical.  However, the Department of Water Resources were
informing water agencies to prepare for a dry 2014 as water
deliveries will be less than normal so the reservoir storage can
recover. In Nevada, drought declarations continued for a
majority of the state, with agriculture the hardest hit from
irrigation restrictions and cattle ranchers selling off more of
their herd due to lack of grazing land.

Hawaii and Alaska: In Hawaii, a couple of remnant frontal rain
bands produced scattered light to moderate showers on the
western half of Hawaii (Kauai, Oahu), helping to mitigate the
worsening of drought conditions there. In the eastern portion of
Hawaii, drier conditions (fewer and lighter showers) were enough
to bridge the two separate D2 areas on the western Big Island as
lack of rain has forced users on catchment systems to haul water
and severely ration usage.

In Alaska, another wet week, especially along the southern (1.5
to 4 inches) and northwestern (0.5 to 1.2 inches) coasts and in
central Alaska (1 to 2.5 inches), allowed for another round of
improvements to the state. Wet weather started in early August
along the south-central coast, and has expanded northward each
week. The recent rains and lower temperatures followed a warm
and dry summer that produced significant deficits for the warm
season. The main impact in the Alaskan interior was the deep
drying of soils and another summer of significant stress on the
primary tree species of boreal forest. Fortunately, there has
been enough rain and a return to seasonable temperatures that
the wildfire season is over; however, long-term deficits
accumulated during the summer still linger in the interior.

Looking Ahead: During September 19-23, a slow-moving frontal
system will trigger showers and thunderstorms from the Great
Plains eastward to the Atlantic Coast, with the largest totals
(more than 1.5 inches) expected along the Rio Grande Valley
eastward along the Gulf Coast and into the Southeast. An inch of
rain is also forecasted from the central Great Plains
northeastward into the upper Great Lakes region, with unsettled
weather returning to the Pacific Northwest. Much drier weather
should return to the Southwest, central Rockies, and High
Plains, allowing for recovery from flooding. Temperatures should
average above normal across the contiguous U.S. except for
subnormal readings in the Far West.

For the ensuing 5 days (September 24-28), the odds favor
enhanced chances for precipitation from the Pacific Northwest
eastward to the upper Midwest, in southern Florida, and along
the southern coast of Alaska. Subnormal precipitation is likely
in northern Alaska and the Tennessee and Ohio Valleys and
eastern Great Lakes region. Above-normal temperatures are
probable east of the Rockies and west of the Appalachians and in
southeastern Alaska while a tilt toward subnormal readings are
forecast for the West and southwestern Alaska.

To contact the reporter on this story: Stephen Rose in Washington at srose31@bloomberg.net

To contact the editor responsible for this story: Marco Babic at mbabic@bloomberg.net

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