**May 2006 NC Weather Review**

**Overview**

Rainfall totals during May were quite variable across North Carolina. It
was generally wetter than normal across portions of the eastern
Piedmont, Coastal Plain, and Sandhills and drier than normal elsewhere.
The driest areas were across the western portions of the state where
Asheville, Charlotte, and Hickory all recorded less than 2 inches of
rainfall. The driest location was in Burlington which recorded only 0.98
inches of rain (3.25 inches below normal). The wettest location was
Scotland Neck in Halifax County which recorded 6.26 inches (2.25 inches
above normal). Not far behind was Elizabeth City with 6.24 inches.

Scattered thunderstorms produced much of the rainfall this month
resulting in the high variability of rainfall across the state. A wide
range in rainfall totals not only existed across the state but even
across counties. The Raleigh-Durham Airport's monthly rainfall total was
only 1.58 inches (2.21 inches below normal), while nearby sites in and
around the city of Raleigh reported between 3 and 4 inches of rain.
Raleigh (N.C. State) reported 3.83 inches. The Raleigh-Durham Airport
location recorded their 5^th^ driest May since records have been kept.

Average monthly temperatures during May generally averaged below normal
by 1 to 3 degrees at most locations. The first 3 weeks of May were
generally cool with only brief 1-2 day warm ups in between cool spells.
Hot temperatures returned around May 24 and lasted through the Memorial
Day weekend. Temperatures reached the mid 80s to lower 90s during the
last week of the month (5-10 degrees above normal).

Soil moisture and stream flow levels continued to slip to near spring
time record low values over the western Piedmont, Foothills, and
Mountains during May. The above normal rainfall over portions of the
eastern Piedmont and coastal region, increased top soil moisture levels
and temporarily increased some of the small stream flows. The main stem
rivers still showed a decline.

![](media/image1.png){width="5.28125in" height="2.1666666666666665in"}

**Figure 1. North Carolina Drought Monitor as of May 30, 2006. Note that
severe drought conditions are now located in western North Carolina in
the Hickory, and Asheville areas.**

The rain was barely enough to put a small dent in the long term drought
conditions. Severe drought conditions were reduced to moderate drought
conditions over some eastern North Carolina counties. However, the
severe drought conditions that shifted toward the Hickory and Asheville
areas in April, took a stranglehold on the southwestern part of North
Carolina in May.

For the latest information concerning the drought, visit
<http://www.ncwater.org/drought/>

**Details**

**May Temperatures**

The average monthly temperatures during May generally ranged in the 60s,
except 50s in the northern Mountains. Greensboro averaged 65.0 degrees
which was 0.8 degrees below normal; Raleigh-Durham averaged 66.5 degrees
(1.5 degrees below normal), Asheville averaged 61.5 degrees (0.5 degrees
below normal), and Wilmington averaged 69.0 degrees (1.2 degrees below
normal).

Overall, monthly temperatures generally ranged around 1 to 2 degrees
below normal across the state. This was the first month with below
normal average temperatures in 2006 at Greensboro and Raleigh-Durham.
The last month with below normal temperatures recorded at both sites was
December 2005. The May 2006 average temperatures are shown below in
Figure 2 below.

Rather cool temperatures dominated the middle two weeks of May 2006.
These cool temperatures were sandwiched between warm spells to begin and
end the month. Daily high temperatures during the middle of the month
frequently remained in the 60s and 70s (10 to 15 degrees below normal).
The hottest weather arrived during the last week of May when daily highs
reached the upper 80s to lower 90s over the interior of the state.
Fayetteville soared to 97 degrees on May 27^th^, the warmest temperature
observed in the state during May.

![](media/image2.png){width="6.989583333333333in"
height="2.9895833333333335in"}

**Figure 2. Average monthly temperatures during May 2006 across North
Carolina.**

An amplified upper level pattern featuring a trough over the eastern
United States and a ridge over the western United States provided the
cooler than normal temperatures over North Carolina during the middle of
May. Figure 3 depicts the average 500 MB pattern across the United
States from May 10 -- May 20, 2006. Note the deep trough over the
eastern United States.

![](media/image3.png){width="4.6875in" height="3.2916666666666665in"}

**Figure 3. Average 500 MB pattern during the middle of May 2006 across
the U.S.**

Figures 4 and 5 shown below and on the following page depict the daily
maximum and minimum temperatures observed at both Raleigh-Durham (RDU)
and Greensboro (GSO) during May 2006. The dashed lines represent the
normal maximum temperature (red) and the normal minimum temperature
(blue). The two week period of below normal temperatures observed in the
middle of the month was noteworthy.

![](media/image4.wmf){width="5.375in" height="3.1979166666666665in"}

**Figure 4. Daily maximum and minimum temperatures observed during May
2006**

**at Raleigh-Durham (RDU).**

![](media/image5.wmf){width="5.333333333333333in"
height="3.1979166666666665in"}

**Figure 5. Daily maximum and minimum temperatures observed during May
2006**

**at Greensboro (GSO).**

**May 2006 Precipitation**

There was a sharp gradient of rainfall across North Carolina during May.
The western sections of North Carolina were drier than normal while
eastern sections were generally slightly wetter than normal. Monthly
precipitation totals generally averaged between 4 and 6 inches across
the east (100 to 125 percent of normal) and only 1 to 3 inches over the
west (30 to 50 percent of normal).

The drought that has plagued portions of interior North Carolina since
the summer of 2005 worsened in May with the lack of rain over the
Mountains, Foothills, and southwest Piedmont. There was much better news
over the eastern sections of the state as near or above normal rainfall
provided mostly short term relief from the drought. Figure 6 depicts the
estimated rainfall for May 2006 from selected National Weather Service
reporting sites. Figure 7 is a comparison of observed versus normal
rainfall for selected NWS sites across the state. Of note this month was
the high variability of observed rainfall and rainfall deficits across
the state. The emphasis was on dry weather across the west and wet
weather in the northeast part of the state.

![](media/image6.png){width="6.997222222222222in"
height="3.2215277777777778in"}

**Figure 6. Estimated Rainfall for May 2006. Plotted data was recorded
by National Weather Service observation systems or cooperative
observers.**

![](media/image7.wmf){width="5.583333333333333in"
height="3.8020833333333335in"}

**Figure 7. Comparison of observed precipitation and normal
precipitation for May 2006 at selected locations across North
Carolina.**

**Severe Weather during May 2006**

Along with the establishment of an upper trough in the eastern United
States during May and the associated increase in thunderstorm activity
came severe weather. One of the most significant severe weather
outbreaks occurred on Mother's Day, Sunday, May 14, 2006. A summary of
this event is available from the National Weather Service in Raleigh
at\...

<http://www4.ncsu.edu/~nwsfo/storage/cases/20060514/>

**Current, Semi-Annual and Annual Temperature Trends**

The cooler than normal temperatures in May 2006 bucked the semi-annual
and annual trend of above normal monthly temperatures. This was the
first month of below normal monthly temperatures since December 2005,
and is only the second month in the past twelve months to have seen
below normal temperatures at Raleigh and Greensboro. Figure 8
illustrates the annual monthly temperature departures from normal at
Greensboro and Raleigh-Durham.

![](media/image8.wmf){width="5.59375in" height="3.59375in"}

**Figure 8. Monthly temperature departures from normal at Raleigh-Durham
and Greensboro from April 2005 through May 2006.**

**Current, Semi-Annual, and Annual Precipitation Trends**

The dry conditions observed across the state since the beginning of 2006
continued to show improvements across eastern North Carolina in May;
however, the drought continued to worsen in the west. The drought
classification had been upgraded to "severe" over much of western North
Carolina by the end of May. The "severe" drought classification which
covered many of the counties across eastern North Carolina was
downgraded to "moderate" drought conditions due to the recent rains in
late April and May.

Raleigh-Durham recorded below normal monthly rainfall again in May. This
was the 4^th^ time in the past 5 months that RDU has recorded below
normal rainfall. Only April was wetter than normal. The 2006 rainfall
deficit was 6.75 inches. Below normal precipitation has been recorded in
8 of the past 12 months, and 10 of the past 15 months. Figure 9 depicts
the precipitation trends at RDU during the past 12 months.

![](media/image9.wmf){width="5.416666666666667in" height="3.3125in"}

**Figure 9. Semi-annual and annual precipitation trends at
Raleigh-Durham (RDU).**

Rainfall during May at Greensboro was 1.50 inches below normal.
Greensboro has been even drier than Raleigh-Durham, as 9 of the past 12
months, and 11 of the past 15 months have been drier than normal. The
2006 deficit alone totaled 7.50 inches below normal. Figure 10 depicts
the monthly precipitation totals and the departure from normal during
the past 12 months at Greensboro.

![](media/image10.wmf){width="5.447916666666667in"
height="3.3645833333333335in"}

**Figure 10. Semi-annual and annual precipitation trends at Greensboro
(GSO).**

**North Carolina Water Resources Information and Outlook**

The general trend of April's stream flow patterns continued into most of
May across North Carolina. A rapid decline in stream flow has been noted
across the Mountains, Foothills, and southwest Piedmont, while
improvements have been seen in the east. The USGS reported that stream
flows had fallen to historic levels with flows in the lowest 10
percentile observed in areas from Charlotte to Asheville to Hickory.
Reservoir levels showed declines throughout the western half of the
state as the inflow levels fell below 50 percent of normal.

To the east, the USGS reported that while improvements in stream flow
had occurred in recent weeks over the eastern Piedmont, Sandhills, and
Coastal Plain, these improvements have been limited to the near surface
layer. Main stem rivers still showed a slight decline overall. When
locally heavy showers have occurred, the streams fill quickly, and then
fall quickly as well. This is an indication that the deeper layers are
still dry. Reservoir levels in the eastern Piedmont stayed near normal
due to continued conservation efforts as their inflow levels remained at
only about 50 percent of normal.

Much more in the way of above normal rainfall is needed to rid the state
from the current drought status. However, the short term water needs
have shown significant improvement for local agricultural needs from
about Raleigh eastward through the Coastal Plain.

**Climate Outlook for the rest of the summer 2006**

The Climate Prediction Center released the latest 3 month climate
outlook recently. Details concerning this forecast can be found at\...

<http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/page2.gif>

![](media/image11.png){width="6.5in" height="3.821527777777778in"}

**Figure 11. The 90-120 Day Precipitation Outlook for the United States
and North Carolina through September 2006**

As can be seen in Figure 11 relief in the drought may be on the way.
According to outlooks from the Climate Prediction Center, the oceanic
and atmospheric indicators in the tropical pacific indicate the recent
La Niña conditions had weakened since April. This allowed the CPC to
reduce the probability of dry conditions over North Carolina for the
remainder of the 2006 spring and into the summer season. There were now
signals supporting a higher than normal probability of returning to
above normal rainfall from July into August and September. This is due
in part to an expected active Atlantic basin tropical season. Figure 11
is the outlook for precipitation probability through September 2006.

In addition, Figure 12 depicts the latest U.S. Seasonal Drought Outlook.
Improvements are expected to occur over the drought stricken areas of
the state in the next few months.

![](media/image12.png){width="5.625in" height="4.34375in"}

**Figure 12 is the U.S. Seasonal Drought Outlook from NOAA. Improvements
in the recent drought are expected to spread from the eastern Piedmont
through the Mountains in the next few months.**

**NC Weather Review Team**

Phillip Badgett

Michael Strickler