April 2013: Earth's 13th warmest April; 92E a threat to Mexico and Guatemala

April 2013 was the globe's 13th warmest April since records began in 1880, according to NOAA's National Climatic Data Center (NCDC). NASA also rated it the 13th warmest April on record. The year-to-date period of January - April has been the 8th warmest such period on record. April 2013 global land temperatures were the 17th warmest on record, and global ocean temperatures were the 7th warmest on record. April 2013 was the 338th consecutive month with global temperatures warmer than the 20th century average. Global satellite-measured temperatures in April 2013 for the lowest 8 km of the atmosphere were 13th or 11th warmest in the 35-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. The Northern Hemisphere snow cover extent during April 2013 was the 9th largest in the 47-year period of record, and the first above-average April snow cover since 2003. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of April 2013 in his April 2013 Global Weather Extremes Summary. He notes that The U.K. had its coldest April since 1989, and a storm felled the Pontfadog Oak, said by some to be Britain’s oldest tree. The historic tree dated back to at least 802 A.D., and was said to have served as a rallying point for a Welsh prince’s army that defeated England’s King Henry II in 1157 A.D.


Figure 1. Departure of temperature from average for April 2013, the 13th warmest April for the globe since record keeping began in 1880. Temperatures were much warmer than average across much of Mexico, the coastal regions of South America, most of Argentina, southern Europe, parts of coastal Africa, far eastern Europe, and western Australia. Record warm temperatures were observed across the southern tip of South America, far western Brazil, the southern Philippines, and some locales in far eastern Russia. It was much cooler than average across a swath of central North America, central Paraguay, part of northwestern Canada, and much of Alaska, where the southeastern portion of Alaska had record cold April temperatures. Image credit: National Climatic Data Center (NCDC) .

One billion-dollar disaster in April: floods in Buenos Aires, Argentina
Torrential rainfall fell across parts of Argentina’s city and province of Buenos Aires between the 2nd and 4th, triggering flash flooding that killed at least 70 and did $1.3 billion in damage, making it the deadliest and most damaging weather disaster world-wide in April. In the city of Buenos Aires, seven hours of heavy rains flooded subways and submerged low-lying neighborhoods. Hardest-hit was the La Plata region, where 400 millimeters (15.74 inches) of rain fell in just two hours. The total was more than the city had ever recorded during an entire month of April. Argentina’s largest refinery, Ensenada, also sustained damage from the floods, plus a fire.

The Argentinian flood in April brought the 2013 tally of billion-dollar weather disasters to six, according to the April 2013 Catastrophe Report from insurance broker AON Benfield. The six billion-dollar weather disasters through April 2013:

1) Drought in Central and Eastern China, 1/1 - 4/30, $4.2 billion
2) Flooding in Indonesia, 1/20 - 1/27, $3.31 billion
3) Flooding in Australia, 1/21 - 1/30, $2.5 billion
4) Winter weather in Europe, 3/12 - 3/31, $1.8 billion
5) Flooding in Argentina, 4/2 - 4/4, $1.3 billion
6) Severe weather in the Midwest U.S., 3/18 - 3/20, $1 billion

Preliminary damage estimates of $2 billion from the May 20, 2013 tornado in Moore, Oklahoma tornado will likely put that disaster on the list for May.


Figure 2. Severe flooding in Buenos Aires, Argentina, on April, 3, 2013 submerged half the city in waters up to 2 meters (6.6') deep. Image credit: focolare.org.

Neutral El Niño conditions continue in the equatorial Pacific
For the 13th month in row, neutral El Niño conditions existed in the equatorial Pacific during April 2013. NOAA's Climate Prediction Center (CPC) expects neutral El Niño conditions to last through summer. The large majority of the El Niño models predict neutral conditions will last through the fall of 2013. Temperatures in the equatorial Eastern Pacific need to be 0.5°C below average or cooler for three consecutive for a La Niña episode to be declared; sea surface temperatures were 0.4°C below average as of May 20, and have been +0.1 to -0.4°C from average since April 1, 2013.

Arctic sea ice falls to 7th lowest April extent on record
Arctic sea ice extent during April reached its seventh lowest extent in the 35-year satellite record, according to the National Snow and Ice Data Center (NSIDC). This was the 12th consecutive April and 143rd consecutive month with below-average Arctic sea ice extent. The last ten years (2004 to 2013) have seen seven of the ten lowest April extents in the satellite record.


Figure 3. Latest satellite image of Invest 92E.

Eastern Pacific tropical disturbance bringing heavy rains to Mexico and Guatemala
Invest 92E in the Eastern Pacific, centered about 100 miles southwest of the Mexico/Guatemala border, will bring very heavy rains capable of causing dangerous flash floods and mudslides to coastal Guatemala and Mexico's Bay of Tehuantepec over the next three days. Radar out of El Mozotal, Mexico shows that heavy rains have already pushed ashore along the Mexico/Guatemala border, and satellite loops show an impressive and expanding area of heavy thunderstorms associated with 92E, with some spiral bands beginning to develop on the storm's south side. In their 5 am PDT Tropical Weather Outlook, NHC gave 92E a 60% of developing into a tropical cyclone by Wednesday. I put these odds higher, at 80%. The 0Z Monday runs of the GFS and ECMWF both predict that 92E could develop into a tropical depression by Tuesday. With wind shear a low 5 -10 knots and ocean temperatures a very warm 30°C, conditions are ripe for further development, and I expect 92E will be a tropical depression or tropical storm when it makes landfall on Wednesday along the Mexican coast in the Bay of Tehuantepec.

In the Atlantic, the models are depicting high wind shear through June 1 over the majority of the regions we typically see May tropical cyclone development--the Caribbean, Gulf of Mexico, and Bahamas. The GFS and ECMWF models are showing a decrease in wind shear over the Western Caribbean after June 1, which would argue for an increased chance of tropical storm development then (though wind shear forecasts more than 7 days in advance are highly unreliable.)


Figure 4. Severe weather outlook for Monday, May 28, calls for a "Moderate Risk" of severe weather over portions of Kansas and Nebraska. You can follow this week's severe weather outbreak from our Severe Weather page.

Multi-day severe weather outbreak in the Midwest begins today
The latest forecasts from NOAA's Storm Prediction Center call for an active severe weather period Monday though Wednesday in the Midwest, with a "Moderate Risk" of severe weather today (Monday) over portions of Northern Kansas and Southern Nebraska. The severe weather outbreak will continue on Tuesday and Wednesday, though SPC is only highlighting a "Slight Risk" of severe weather on those days at present.

Have a great Memorial Day, everyone!

Jeff Masters