**August 2006 NC Weather Review**

**Overview**

August 2006 was a predominately hot and dry month. Consequently,
incipient abnormally dry areas across much of northern and central North
Carolina were once again declared a region of moderate drought by August
25. However, the hot and dry pattern abruptly ended during the last two
days of the month, when a cold front and a tropical storm produced
thunderstorms, heavy rain, flooding, and cooling temperatures. The
resultant heavy rain during the last two days of the month then
eliminated the moderate drought conditions over central North Carolina.

The monthly rainfall totals in August 2006 were heavily influenced by
tropical storm Ernesto over eastern North Carolina. It was much drier in
the western sections, as the rainfall directly associated with Ernesto
passed to the east. The monthly rainfall totals ranged from less than 2
inches over portions of western and northern North Carolina, to over 18
inches at Wilmington. The coastal area was the wettest region, where
between 10 and 18 inches were reported. The northern Piedmont was the
driest area, where less than 2 inches was reported. Rainfall totals from
selected stations across North Carolina for the month of August are
plotted in Figure 1.

Ernesto not only brought significant rain and flooding down east, but
the associated enhanced clouds and rain brought cooling relief to the
state on the last day of the month. However, it was quite hot throughout
much of August, with almost no penetration of cool air masses from the
north. Raleigh-Durham had a string of 7 straight 90 degree days broken
by Ernesto's clouds and rain on the 31^st^. The statewide average August
temperatures generally ranged between 78 and 81, except cooler mid 60s
to mid 70s over the Mountains. These readings generally averaged 2 to 3
degrees above the 30 year normal. The average monthly temperatures from
selected stations across North Carolina are plotted in figure 2.

![](media/image1.png){width="6.995138888888889in"
height="3.140277777777778in"}

**Figure 1. Estimated Rainfall for August 2006. Plotted data was
recorded by National Weather Service observation systems or cooperative
observers.**

![](media/image2.png){width="6.989583333333333in"
height="3.2291666666666665in"}

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

**Details**

**August 2006 Temperatures**

The hot and dry conditions that gripped North Carolina through the
majority of the month were halted by a pattern change, which occurred
just in time to allow tropical storm Ernesto to turn northward over
coastal eastern North Carolina on the final day of the month. A strong
and persistent subtropical ridge of high pressure across much of the
southern United States, depicted in Figure 3, was responsible for the
hot and dry weather for much of August. However, a trough of low
pressure, depicted in figure 4, developed over the Great Lakes and
extended southward into the lower Ohio Valley during the last week of
August. This trough not only allowed a more moist southwest flow aloft
to bring increased thunderstorms to the state on the 30^th^, it also
allowed aforementioned Tropical Storm Ernesto to be steered from Florida
northward along coastal North Carolina on the 30^th^ and 31^st^.

The monthly temperatures across the state generally averaged well above
normal. Much of the interior of the state averaged 3 degrees or more
above normal, including Lumberton (+3.3 degrees), Fayetteville (+3.3
degrees), Raleigh-Durham (+3.3 degrees), and Greensboro (+3.2 degrees).
Only the immediate coast saw temperatures that were nearer to normal,
including Wilmington (+0.8 degrees) and Elizabeth City (+0.6 degrees).

![](media/image3.png){width="4.864583333333333in"
height="4.010416666666667in"}

**Figure 3. The average 500 MB pattern over the United States during the
first half of August 2006.**

![](media/image4.png){width="4.833333333333333in" height="3.96875in"}

**Figure 4. The average 500 MB pattern over the United States during the
last few days of August 2006.**

Aided by the upper ridging over North Carolina, evident in Figure 3,
there were numerous days in which the temperatures reached or exceeded
90 degrees over the interior of North Carolina. Figure 5 depicts the
number of 90 degree days this year at selected reporting sites in North
Carolina for the summer of 2006.

![](media/image5.wmf){width="5.15625in" height="3.2708333333333335in"}

**Figure 5. The number of days in which selected stations across North
Carolina have reached or exceeded 90 degrees this year (through August
31). As is typically the case, the mountainous areas and locations along
the immediate coast reported the least number of 90 degree days so far
this season. Boone (elevation of 3000 feet) has yet to record a 90
degree day, while Cape Hatteras (surrounded by water) has only recorded
2. The Sandhills and southern Coastal Plain sections in southeastern
North Carolina led the list of the hottest areas. Fayetteville and
Lumberton led the way with 60+ 90 degree days reported.**

Figures 6 and 7 depict the daily maximum and minimum temperatures
observed at Raleigh-Durham (RDU) and Greensboro (GSO) during August
2006. The dashed lines represent the normal maximum temperature (red)
and the normal minimum temperature (blue). Note there were only a couple
of brief cool downs during the entire month, until Ernesto hit on August
31 and kept temperatures well below normal that day.

![](media/image6.wmf){width="5.375in" height="3.1979166666666665in"}

**Figure 6. Daily maximum and minimum temperatures observed during
August 2006**

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

![](media/image7.wmf){width="5.333333333333333in"
height="3.1979166666666665in"}

**Figure 7. Daily maximum and minimum temperatures observed during
August 2006**

**at Greensboro (GSO).**

**August 2006 Precipitation**

The rainfall during the first 29 days of the month was sporadic and
could be attributed to typical summertime, diurnal thunderstorm
activity. This produced a highly variable rainfall distribution pattern
across the state. While some areas received a thunderstorm or two each
week, other locales did not see a decent rainfall during the entire 29
day period. A good example of the relative dryness and sporadic rainfall
during the first four weeks of the month was noted across the central
Piedmont, including the Triangle.

At the RDU International Airport, a total of 4.42 inches of rain fell
during August; however, 1.78 inches of that total (40 percent) fell on
the last day of the month. On the other hand, local cooperative
observers at nearby Raleigh (NCSU) and Cary totaled 2.75 inches of
rainfall for August. These sites missed out on thunderstorms that hit
nearby locations around RDU at times during the month. In fact, an
astoundingly low 0.36 of an inch of rain was all that fell at Raleigh
(NCSU) in the first 29 days of the month. This was only 5 percent of
normal. A total of 2.36 inches fell at Raleigh (NCSU) on the last two
days of the month (87 percent of the monthly total). Since this extreme
dryness seen at Raleigh (NCSU) and Cary from August 1-29 was fairly
localized to portions of the central Piedmont, it mainly affected the
local agricultural community. Wilted crops, brown lawns, and premature
falling leaves from the moisture deprived deciduous trees were common.

This dry flavor to the month changed dramatically by months end. A
weakening cold front pushed into North Carolina from the north on August
30^th^. This front was accompanied by the development of widespread
thunderstorms during the afternoon and evening hours. Rainfall amounts
of between 1 and 4 inches were common throughout central North Carolina,
where flash flooding occurred in some areas of the Piedmont.

Widespread rain moved into the state on the 31^st^, courtesy of Tropical
Storm Ernesto.. The shield of heavy rain inundated southeastern North
Carolina during the afternoon hours; however Ernesto did not make
landfall near Long Beach (Brunswick County) until late in the evening on
the 31^st^. Rainfall totals associated with Ernesto ranged from 5 to 10
inches around the Wilmington and Jacksonville areas. This boosted
monthly totals to between 15 and 18 inches in this region of the state.
The tropical storm then moved north-northeast through eastern North
Carolina overnight, and produced very heavy rainfall and flooding across
the coastal area. The heaviest rainfall occurred over the central and
northern coastal sections after midnight on September 1, 2006. Rainfall
from August 31 through September 1 associated with the tropical storm,
is depicted in figure 8. Figure 9 shows some of the flooding observed in
Edgecombe County.

![](media/image8.png){width="6.989583333333333in" height="3.53125in"}

**Figure 8. Precipitation analysis of the rainfall associated with
Tropical Storm Ernesto.**

![](media/image9.jpeg){width="4.027083333333334in"
height="3.017361111111111in"}

**Figure 9. Flooding in Edgecombe County near Princeville, after
Tropical Storm Ernesto. Photo courtesy of the NWS Raleigh Service
Hydrologist, Michael Moneypenny.**

Figure 10 is a comparison of observed versus normal rainfall for
selected NWS sites across the state. Of note were the abnormally wet
conditions from Wilmington to Elizabeth City, which were largely a
result of Ernesto. The rainfall was generally above normal elsewhere,
but not excessively so.

![](media/image10.wmf){width="5.583333333333333in"
height="3.8020833333333335in"}

**Figure 10. Comparison of observed precipitation and normal
precipitation for August 2006 at selected locations across North
Carolina.**

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

A persistent upper level ridge typically means above normal
temperatures, and that was the case for the majority of August. The
temperatures during August generally averaged well above the 30 year
normal for central North Carolina reporting stations. Greensboro and
Raleigh averaged a whopping 3.3 degrees above normal.

Figure 11 illustrates the annual monthly temperature departures from
normal at Greensboro and Raleigh-Durham. Eleven of the past thirteen
months have been warmer than normal at Greensboro, and ten of the past
thirteen have been warmer than normal at Raleigh-Durham. December 2005
and May 2006 have been the only months in the past year that averaged
significantly cooler than the 30 year normal.

![](media/image11.wmf){width="5.59375in" height="3.59375in"}

**Figure 11. Monthly temperature departures from normal at
Raleigh-Durham and Greensboro from August 2005 through August 2006.**

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

Wet conditions returned the last two days of August, which ended the
extended dry period that began in some areas in July. Abnormally dry
conditions quickly turned into a moderate drought again for some areas
by the last week in August. Rain from Tropical Storm Ernesto eased the
drought rather quickly by September 1.

Overall, August continued the recent wetter than normal monthly trends
over portions of northwestern and eastern North Carolina. The lower than
normal rainfall totals over portions of the central Piedmont continued
the recent trend of dryness there.

The 4.42 inches of rain recorded at Raleigh-Durham was slightly above
normal by August standards. This was the third time in the past six
months that RDU has recorded above normal rainfall. RDU had a yearly
rainfall surplus of 0.06 of an inch on August 31. Figure 12 depicts the
precipitation trends at RDU during the past 12 months. The above normal
rainfall during June and August can be greatly attributed to the
remnants of Alberto and Ernesto.

![](media/image12.wmf){width="5.416666666666667in" height="3.3125in"}

**Figure 12. Semi-annual and annual precipitation trends at
Raleigh-Durham (RDU).**

The 5.29 inches of rain recorded at Greensboro was 1.58 inches above
normal for August. Three consecutive months of above normal rainfall has
allowed Greensboro to complete a dramatic turn from a 7.50 inch 2006
rainfall deficit at the start of June, to a 3.00 inch surplus by August
31. Figure 13 depicts the monthly precipitation totals and the departure
from normal during the past 12 months at Greensboro. Note the huge
surplus in rainfall during June, July, and August after 5 consecutive
very dry months.

![](media/image13.wmf){width="5.447916666666667in"
height="3.3645833333333335in"}

**Figure 13. Semi-annual and annual precipitation trends at Greensboro
(GSO).**

**North Carolina Water Resources Information and Outlook**

There were short-term agricultural water concerns across portions of the
southern Piedmont and Sandhills at the end of July, due to the lack of
rainfall. These concerns spread to cover much of the central Piedmont
during August. Soil moisture and stream flow levels began to decline
beneath the hot August sun; and it became so dry over portions of
central North Carolina that the US Drought Monitor classification
increased from abnormally dry to a moderate drought. Most crops failed
to get adequate moisture across much of central North Carolina during
the majority of August. Heavy rain during the last two days of the month
changed the outlook dramatically across much of the state.

After rain from Ernesto on August 31 and September 1, drought no longer
was a major concern for most areas. The moderate drought classification
was reduced to abnormally dry from the Mountains east to Raleigh. Figure
14 is the US Drought Monitor of North Carolina as of September 5, 2006.
Much of North Carolina was generally drought free. Many of the
reservoirs that supply water to major metropolitan areas of the Triad
and Triangle regions returned to full pool levels by September 1.

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

![](media/image14.png){width="5.135416666666667in" height="2.875in"}

**Figure 14. North Carolina Drought Monitor as of September 5, 2006.**

**Climate Outlook for the fall 2006**

The Climate Prediction Center released the most recent 3 month climate
outlook recently. Details concerning this forecast can be found at the
web address below\...

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

According to outlooks from the Climate Prediction Center, there were
signals of a developing El Nino through the fall and winter seasons. El
Nino conditions in the equatorial Pacific can bring increased rainfall
and below normal temperatures to portions of the southeastern U.S.,
including North Carolina, during the winter season. Look for much more
information concerning this developing El Nino in subsequent monthly
outlooks.

Figure 15 depicts the latest U.S. Seasonal Drought Outlook. The
abnormally dry areas in western North Carolina are expected to show
improvement through the fall season. It is quite possible that most of
the state will be drought free before the end of 2006.

![](media/image15.png){width="5.625in" height="4.34375in"}

**Figure 15 is the U.S. Seasonal Drought Outlook from NOAA. Improvements
in the recent drought over North Carolina are expected to continue in
the next few months.**

**NC Weather Review Team**

Phillip Badgett

Michael Strickler