2015 Climate Summary of the Southeastern United States

Highlights

Following a record warm December, 2015 wrapped up with more abnormal climatic conditions. Nearly every state in the Southeast experienced much above normal temperature conditions (Fig. 1) and above average precipitation totals (Fig. 2). Florida, however, was around the precipitation average. Additionally, there were some significant climate anomalies throughout the year. A strong El Nino formed across the equatorial Pacific and peaked towards the end of the year. The North Atlantic hurricane season was slightly below average with 11 named storms, 4 hurricanes, and 2 major hurricanes. In October, Hurricane Joaquin interacted with an upper level low, which lead to historic rainfall amounts across the Carolinas. Around Charleston, South Carolina rainfall amounts were around 15-20 inches with isolated amounts of up to 25 inches. Severe weather swept across the south in late December, which caused tornadoes and record flooding. Lastly, Florida has its warmest year on record with an average statewide temperature of 3.3°F above normal.

Figure 1. Statewide average temperature ranks for January - December of 2015, Source: NOAA/NCEI

Figure 2. Statewide precipitation ranks for January - December of 2015, Source: NOAA/NCEI

Seasonal Analysis 

A prominent trough remained over much of the Southeast during the winter months. Consequently, most of the states experienced a below average winter, while Florida, Georgia, and South Carolina were around normal. Most of the lower Mississippi Valley experienced drier than normal conditions while the other Southeastern states were around normal precipitation totals for remainder of the winter season. 

By spring, the pattern shifted as most of the Southeast experienced above average temperatures and Florida set a new spring temperature record (4.6°F above average). Nighttime temperatures were much above normal, which allowed the average temperature to exceed above normal conditions. As for precipitation amounts, the southeast experienced a mix of climatic anomalies by the end of May. The lower Mississippi Valley had above normal precipitation amounts while Florida, North Carolina, and South Carolina experienced drier than normal conditions. The remaining Southeastern states were around their normal precipitation totals. Additionally, Tropical Storm Ana made landfall on May 10th near Myrtle Beach, South Carolina. Little damage was reported, but heavy rain fell across the Carolinas. 

Florida, Louisiana, North Carolina, and South Carolina experienced much above normal temperature conditions by the end of the summer. Kentucky and Tennessee remained around average temperatures by August while the rest of the Southeastern states were warmer than average. Below-average precipitation fell across the Southeast. Combined with warm temperatures, drought conditions worsened across the lower Mississippi Valley and Southeast. In contrast, above-average precipitation fell across Kentucky, Tennessee, and Virginia. In August, remnants of Tropical Storm Erika moved across Florida, which helped alleviate drought conditions. 

Every Southeastern state had an above-average fall temperature. Florida had its warmest fall on record with the statewide average around 3.6°F above the norm. As for precipitation, every state (except Florida) had above-average precipitation amounts by the end of fall. The historic flooding event in early October caused South Carolina to have its wettest fall on record with 23.76 inches (13.91 inches above average). Due to the rainfall, drought conditions improved across the entire Southeast.

Atlantic Hurricane Season 

Figure 3. 2015 Atlantic hurricane season with storm tracks and strength, source: NOAA National Hurricane Center

The 2015 Atlantic hurricane season had 11 named storms, 4 hurricanes, and 2 major hurricanes (Fig. 3). The season was slightly below the climatological mean. On average, 12.1 named storms occur with an average of 6.4 hurricanes and 2.7 major hurricanes. The lack of activity could be due to the El Nino, which tends to suppress Atlantic hurricane activity.

Two tropical storms made landfall (Ana and Bill) and no hurricane or major hurricane made landfall this season. Hurricane Joaquin did not make landfall; however, it did interact with an upper level low, which caused historic flooding in the Carolinas. This season continued the record-long streak of no major hurricane (category 3 and higher) making landfall. On average, a major hurricane makes landfall every 3 years. The last major hurricane to make landfall was Hurricane Wilma, which was November 24, 2005. 

Severe Weather Season

Figure 4. 2015 tornado occurrences in the United States, Source: NOAA Storm Prediction Center

For the United States, the preliminary report of tornadoes was around 1, 183. This season was below the climatological average, which is 1, 253 annually. Most months were around the climatological mean for tornado reports. However, May, November, and December were well above their respective averages. In May, there were 414 confirmed tornado reports, which is 138 above the average. In November, there were approximately 95 preliminary reports, which is 37 above the average. In December, there were 86 preliminary reports, which is 62 above average. Lastly, in the Southeastern U.S., there were no tornado reports, which was the first time that at least 1 tornado was not reported in the region. 

Reference: 

NOAA National Centers for Environmental Information, State of the Climate: National Overview for Annual 2015, published online January 2016, retrieved on January 28, 2016 from http://www.ncdc.noaa.gov/sotc/national/201513

Southeast Climate at a Glance - December 2015

Following a mild November, December 2015 was also warm and wet across the region. The entire Southeast experienced above average temperatures and precipitation totals during December. In fact, many states set new temperature records. Specifically, nine states set December records for their statewide average temperature, maximum temperature, and minimum temperature.

Temperature Summary 

December temperatures were much above average with some locations reaching the 70s and 80s. Many weather stations observed record-breaking temperatures throughout the month. Virginia, Kentucky, Tennessee, North Carolina, South Carolina, Georgia, Florida, Alabama, and Mississippi experienced their hottest December on record (Fig. 1). Most of the region was 9 to 14 degrees F above their mean temperature norm, while southern Florida was 6 to 9 degrees F above their mean. The warmest part of December was the 24th through the 27th as maximum temperatures reached the 70s and minimum temperatures remained in the 60s. The coolest part of the month was the 19th and 20th as minimum temperatures fell below 30 degrees F over most of the Southeast. 

Figure 1. Statewide average temperature ranks for the month of December. Source: NOAA/NCEI

Precipitation Summary

Most of the region observed above average precipitation totals by the end of December. In total, eight states (Virginia, Kentucky, North Carolina, South Carolina, Georgia, Alabama, and Arkansas) observed well above average precipitation totals (Fig. 2). Stations in Alabama, Georgia (except the southeastern quadrant), northern South Carolina, North Carolina, south-central Virginia, the Florida Panhandle, and southern Florida recorded precipitation totals 200 to 600 percent of normal. Stations across central and northern Florida and southeastern Georgia recorded precipitation totals 5 to 50 percent of normal. 

Figure 2. Statewide precipitation ranks for the month of December. Source: NOAA/NCEI

Drought and Climate Impacts on Agriculture

There were no drought conditions (class D1 or greater) present during December. 

There were some damaged agriculture reports across the region. Heavy rainfall events caused flooding over southeastern Florida and damaged winter yellow squash, zucchini, and green beans. In Georgia, farmers were unable to harvest a significant amount of their pecan groves due to saturation. Lastly, lack of cold temperatures (specifically between 32 and 45 degrees F) in Georgia reduced the necessary winter dormancy for peach trees and blueberry bushes. This will likely negatively affect the yield in 2016.  

In Summary

A couple contributing factors to the abnormal December climate is the El Nino and Arctic Oscillation. El Nino tends to enhance the subtropical jet stream, which directs storm tracks along the southern states. An El Nino normally causes above normal precipitation totals across the southern states during the winter months. In regards to the temperature, the Arctic Oscillation was positive for the majority of December. This means that the Arctic air is trapped in the polar region. Consequently, arctic air masses remained north while southerly flow directed warm air in the region causing above normal temperature conditions. 

NOAA National Centers for Environmental Information, State of the Climate: National Overview for December 2015, published online January 2016, retrieved on January 13, 2016 from http://www.ncdc.noaa.gov/sotc/national/201512.

Raleigh December Climate Summary

Winter in the southeastern United States is usually mild, but this past December was far from normal. December 2015 ranked as the hottest December on record average maximum, mean, and average minimum temperature for the Raleigh weather station. Across the entire state, almost every station recorded its warmest December on record for mean temperature and a few others recorded their second warmest. Along with warm temperatures, total precipitation was about 3 inches above normal for Raleigh.

Temperature

The mean average temperature was 56.1F, which is 12.7F above normal! December 2015 ranked as the hottest December ever recorded for Raleigh. Raleigh experienced a few cold days, but overall the temperature was much above normal (Fig. 1). The warmest day was Christmas Eve as the temperature topped at 77F. The average maximum temperature was 65.1F, which is 11.6F above normal. The average minimum temperature was 47.1F, which is 13.8F above normal. 

Figure 1. The average mean temperature during December for Raleigh

Precipitation

The first half of December was relatively dry with only a few light rain events around 0.04". The second half of December was active which caused the total precipitation to surpass the normal amount (Fig. 2). Raleigh received 6.07" of rain, which is 3.00" above the norm. Overall, December 2015 ended with the 11th wettest December on record. 

Figure 2. The total precipitation amount during December for Raleigh

Why was it so warm?

There are many natural climate oscillations that have a big impact on our climate. Studies show that the El Nino-Southern Oscillation influences our climate during the winter months. An El Nino enhances the subtropical jet, which directs storms along the southern states. This pattern normally causes above normal precipitation anomalies along the southern states (much like we observed during December). Another climate oscillation that greatly influenced this past December is the Arctic Oscillation (AO). Studies have shown that the AO impacts our wintertime temperatures. A positive AO indicates that the pressure system is strong, which traps the Arctic air in the north. A negative AO means that the pressure system is weaker, which allows the frigid air to move equatorward. Figure 3 shows that the AO was positive for much of December. 

Figure 3. Arctic Oscillation observations and forecasts. Data source: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif 

Additionally, the surface and upper air pattern directed the warm, moist air from the equator up towards the midlatitudes (Fig. 4). Following a record warm autumn, December was far from normal, too. 

Figure 4. Upper air map at 500 mb. Black lines are lines of constant pressure (isobars), dashed red lines are lines of constant temperature (isotherms), and blue flags indicate wind speed and direction in knots. Source: http://www.spc.noaa.gov/cgi-bin-spc/getuadata.pl?MyDate1=151224&Time1=12&MyDate2=&Time2=12&align=V&Levels=500

The remainder of winter

A weather pattern shift occurred in the beginning of January causing Raleigh to experience below normal conditions for both temperature and precipitation thus far. The AO shifted negative, which caused the temperature pattern to be below/around normal. The remainder of January should be below normal for temperature and precipitation. If the storm tracks follow along the southern states and into the Gulf of Mexico, we could see a winter storm. As for February and March, the climate models indicate that the temperature could swing either direction (above or below normal) and the precipitation should be above normal (which is indicative of an El Nino pattern). 

Hurricane Patricia - One of the most powerful hurricanes on record.

At 12:00 UTC (8 a.m. EDT) on October 23rd, Hurricane Patricia became the most intense tropical cyclone in recorded history (globally) as it sustained wind speeds at 200 mph. Patricia grew from a tropical storm to a category 5 hurricane in 24 hours. Making Hurricane Patricia the greatest intensity rate (100 mb in 24 hours) in recorded history. When Hurricane Patricia intensified to 879 mb, it became the 5th most intense tropical cyclone in terms of minimum central pressure.

Satellite image of Hurricane Patricia 

Rapid Intensification 

The sea surface temperatures (SST) across the equatorial pacific have been above-normal for most of this year, indicating that El Nino conditions will likely occur during the 2015/2016 winter season. After Patricia organized, it propagated east/northeast over very warm SSTs. The environmental conditions were favorable for Patricia to intensify. There was very little wind shear, no dry air intrusion, and warm SSTs. The SSTs were around 30℃ (86℉). 

Sea surface temperatures across the equatorial pacific. source: http://www.ssd.noaa.gov/PS/TROP/DATA/RT/SST/PAC/20.jpg

Previous studies indicate that El Nino conditions can increase the likelihood of hurricane activity in the east Pacific ocean (Camargo et al. 2007). El Nino normally causes positive SST anomalies across the equatorial pacific as well as decreasing wind shear. However, the presence of El Nino was not the soul contributing factor to Hurricane Patricia's rapid intensification. For the past two years, there has been a consistent "blob" along the west coast of North America. The "blob" is a large area of above-normal SSTs, which might be in association with the Pacific Decadal Oscillation (PDO). Like the El Nino-Southern Oscillation (ENSO), the PDO goes through warm and cool phases. However, the PDO phases are every 20-30 years. Like ENSO, the PDO is in a warm phase, which is manifest with the above-normal SSTs along the pacific coast of North America. The combination of these two climate oscillations created favorable conditions for Hurricane Patricia to intensify rapidly. Additionally, with climate change, the ocean and atmospheric temperatures have increased, too. This combination of natural climate variability and climate change have increased the baseline temperature, which inherently allows the atmosphere to hold more water vapor. Therefore, there's more water available for tropical cyclones.

Satellite Movie Sees Record-Breaking Hurricane Patricia

Landfall
Patricia made landfall at approximately 7:15 p.m. EDT on Friday, October 23 near Cuixmal, Mexico as a category 5 hurricane. Which was only the second Pacific Hurricane on record to make landfall as a category 5. The maximum sustained wind speeds were 165 mph as it made landfall. This is the second most intense tropical cyclone to make landfall on record. Hurricane Patricia is behind Typhoon Haiyan, which made landfall with sustained winds of 174 mph.

What's in store for Patricia now?
Once Hurricane Patricia made landfall, it weakened to a tropical depression in 16 hours and combined with an upper-level low pressure system to cause rain across the southeast. The remnant of Patricia and the upper-level low caused extreme heavy rainfall over Texas, which caused more local flooding. Also, the combined systems are expected to continue across the southeast with the possibility of heavy rainfall and flash flooding.

24 hour total quantitative precipitation forecast. Source: http://www.wpc.ncep.noaa.gov/qpf/fill_94qwbg.gif?1445875070494

References:

Suzana J. Camargo, Kerry A. Emanuel, and Adam H. Sobel, 2007: Use of a Genesis Potential Index to Diagnose ENSO Effects on Tropical Cyclone Genesis. J. Climate, 20, 4819–4834.

doi: http://dx.doi.org/10.1175/JCLI4282.1

November Climate Summary - The Southeast

This is the first in a new climate summary series called Monthly Southeast Climate at a Glance. Aurelia Baca, SERCH Climate Specialist, will review NOAA/NCEI monthly climate summaries and provide temperature and precipitation highlights for the Southeastern region, along with impacts to agricultural and forestry sectors.

November Southeast Climate at a Glance

Temperature Summary

November was another warm and wet month for the entire Southeastern United States. Every Southeastern state observed well above average temperatures (Figure 1) as well as many temperature extremes. In fact, Florida experienced their warmest maximum temperature for the month of November. Alabama, Florida, southern Georgia, and western Virginia experienced the greatest deviations over the region. The monthly temperatures were 5-9 °F above the average.

Fig. 1. Statewide average temperature ranks for November. Source: http://www.ncdc.noaa.gov/sotc/service/national/statewidetavgrank/201511.gif

The warmest weather occurred from the 4th to the 7th. During this time, maximum temperatures exceeded 70°F across most of the southeast with some areas reaching the upper 80s °F and lower 90s °F. The coolest weather of the month occurred a few weeks later on the 23rd and 24th. The minimum temperature reached the 20s °F across much of the region. 

Precipitation Summary

Along with above average temperatures, every Southeastern state observed above normal precipitation totals (Figure 2). Arkansas experienced their wettest November on record. Louisiana, Alabama, Georgia, South Carolina, and North Carolina were well above their respective average with monthly precipitation totals 150 to 300 percent of normal. The northern locations of the southeast and central Florida were the driest areas where precipitation totals were 25 to 50 percent of their normal.

Fig. 2. Statewide precipitation total ranks for November. Source: http://www.ncdc.noaa.gov/sotc/service/national/statewidepcpnrank/201511.gif

Consistent precipitation alleviated much of the drought conditions over the Southeast. Drought-free conditions (less than D1) increased from 98 to 100 percent by December 1st. The moderate drought (D1) conditions that were present in west-central Alabama, southern Georgia, and the Florida panhandle diminished as consistent precipitation fell across the region. 

Climate Impacts on Agriculture

The above average temperature and precipitation caused some issues among the agricultural sector. The abnormally warm and wet climate caused delayed harvest and reduced the quality of crops across the Southeast. Farmers in Georgia reported their pecan orchards sprouted prematurely. Also, Carolina farmers reported their harvest on cotton, soybeans, and peanuts were poor due to the above average precipitation. 

Conclusions 

The above average precipitation is most likely indicative of El Nino's influence on our weather pattern. Similar conditions are likely to persist throughout the remainder of December causing mild weather conditions for the end of 2015.

References:
NOAA National Centers for Environmental Information, State of the Climate: National Overview for November 2015, published online December 2015, retrieved on December 14, 2015 from http://www.ncdc.noaa.gov/sotc/national/201511 

Raleigh November Climate Summary

The Holiday season is quickly approaching and the weather certainly doesn't agree. This November was much above normal for Raleigh, North Carolina. November was warm and wet. 

The average temperature was 55.43F, which was 3.16F above our norm. For Raleigh, this November was the sixth warmest November on record. In fact, 19 out of 30 days were above normal. Both the maximum and minimum temperature were much above normal, too (1.8F and 4.53F, respectively). See Figure 1 for more details. 

Fig. 1. November average temperature for KRDU. Data source: NCDC

November precipitation was much above normal, too. The total precipitation for Raleigh was 7.14", which is 4.02" above the norm. November was the sixth wettest November on record. See Figure 2 for more details. 

Fig. 2. Daily November precipitation totals for KRDU. Data source: NCDC

December will likely follow a similar trend. Most of the Southeastern U.S. is expected to experience above normal temperatures (figure 3) and above average precipitation (figure 4). 

Fig. 3. One-month temperature outlook. Source: http://www.cpc.ncep.noaa.gov/products/predictions/30day/off15_temp.gif

Fig. 4. One-month precipitation outlook. Source: http://www.cpc.ncep.noaa.gov/products/predictions/30day/off15_prcp.gif

The above average precipitation is most likely in association with El Nino. As stated in the previous post, El Nino tends to enhance the subtropical jet, which causes storms to track across the Southeast. Inherently causing above average precipitation across the Southeast. 

Overall, November was warm and wet. With a little help from El Nino, December will likely be a similar story. 

2015-2016 Winter outlook

El Niño 

The current El Niño is on track to be one of the largest on record (since 1950). This past week's sea surface temperature (SST) anomalies (figure 1) were much above normal with some peaking at 3°C above normal. Although these values are unprecedented, it is not indicative of the events strength. The Climate Prediction Center compares historical El Niño episodes based off of their 3-month SST anomaly mean. The latest Oceanic Niño Index was a 3-month mean over August, September, and October. For this current episode, it was 1.7°C above normal. For comparison, the 1997/1998 El Niño (strongest on record) was 2.0°C above the norm.

FIG 1. Sea Surface Temperatures over the equatorial pacific. source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstweek_c.gif

Every El Niño episode is slightly different. They reach peak intensity at different times and cause various deviations from climatic norms. With that said, the current El Niño has the potential to surpass the 1997/1998 event. Most climate models are in agreement that this episode will peak during the winter and transition to neutral conditions in the spring/summer of 2016.

Southeast Winter Outlook

So, what does this mean for North Carolina? Normally, an El Niño enhances the subtropical jet stream causing storms to track along the southern states of the US. As a consequence, above average precipitation is expected across the Southeast and North Carolina (figure 2).

FIG 2. Climate Prediction Center 3-month precipitation outlook. source: http://www.cpc.ncep.noaa.gov/products/predictions/long_range/lead01/off01_prcp.gif

 As for temperature, that's a little bit more tricky. Sometimes an El Niño can cause above average temperature, while other episodes cause below normal. This winter season was no exception of a tricky outlook. Most of North Carolina could experience either above or below normal temperatures, while the northern tier will likely experience above normal temperatures within the next three months (figure 3).

FIG 3. Climate Prediction Center 3-month temperature outlook. source: http://www.cpc.ncep.noaa.gov/products/predictions/long_range/lead01/off01_temp.gif

My Take:

This El Niño is rivaling the 1997/1998 El Niño in strength. With that said, 1998 was one of the warmest years on record globally and 2015 is on track to be the warmest year on record. I expect December to be above average for both temperature and precipitation. Going into 2016, it is a bit more difficult to say what the temperature deviation will be. As many of you may remember the past two winters, the Arctic Oscillation (AO) plays a strong role for our temperatures. The AO is also difficult to predict well in advance (it switches phases in weeks or sometimes days). If the AO weakens, we will expect to have cold temperatures in our area like the past two winters. Also, because El Niño causes storms to track along the southern states, if the temperatures are in place, we could see a storm or two. However, I do not expect this winter to receive above normal snowfall. For most of the winter, I believe it will be above normal for temperature and precipitation.