Hi Everyone, Friday map discussion for 13 April focused on: 1) the March 2012 CONUS climate revisited, 2) the possibility of a subtropical cyclone over the North Atlantic as advertised by sone recent deterministic and ensemble runs of the GFS and ECMWF, and 3) the weekend severe weather threat over the Central U.S. To restart the debate about putting the March 2012 CONUS climate into perspective, I dangled bait in the form of the CONUS March temperature time series for 1895-2012 (attached; source: NCDC). March 2012, with a mean temperature of 51.1 F, was the warmest March month on record between 1895 and 2012. The second warmest March with a mean temperature of 50.6 F occurred 102 years earlier in 1910. Relative to the overly simplified 1895-2012 linear trend, March 1910 was warmer than March 2012. I showed this example to make the point that we need to be very careful about directly attributing the regional CONUS heat wave of March 2012 to ongoing climate change (a good part of the NH had below normal temperatures in March 2012). The March 1910 CONUS mean temperature was an extreme outlier until March 2012…..and it occurred with far less carbon dioxide and methane in the atmosphere than 102 years later. We would need a cluster of March months as warm or warmer than 2012 over the next couple of decades before we could be somewhat confident that such events are likely manifestations of climate change. A real scientific opportunity exists to determine what physical processes contributed to the extreme warmth over the CONUS in 1910, whether any of these physical processes were in play in March 2012, and why the time scale of these two extreme events is ~100 years. Prompted by the spirited discussion that erupted over the dangled bait which was taken hook, line, and sinker, we revisited another remarkable past climate outlier: Extreme summer warmth over the Plains in the 1930s. Attached are three additional time series (source: NCDC) of July-August mean temperature time series for 1895-2011 for the: 1) CONUS, 2) Central US, and 3) South. For the CONUS, the extreme July-August warmth of the 1930s, in which the mean temperature exceeded 76 F, never came close to being matched or exceeded until July-August 2011. As was the case with the March 2012 mean CONUS temperature, relative to the upward linear trend in the CONUS mean temperatures during July-August, 1910 is still the heat champ. On a more regional scale, where interannual variability can be greater, the July-August warmth experienced over the Central US in the 1930s has never come close to being matched through 2011 (next warmest July-August periods in the early 1960s were ~4 F cooler). However, over the South, July-August 2011 was the warmest on record by ~1.5 F between 1895-2011. Bottom line: How you look at the data matters. The averaging period matters. The perspectives derived from looking at the different datasets matter. Summers for many of the years in the 1930s were remarkably hot and dry (dust bowl era). So hot and so dry that a depopulation of the Plains ensued with many folks relocating to California along the famous dust bowl highway known as Rt. 66. The hot and dry summers of the 1930s represent another natural climate outlier (there was also a lot less carbon dioxide and methane in the atmosphere as compared to today) begging to be understood, particularly with regard to what element(s) these earlier hot and dry summer years may have had in common with the summer of 1980 over much of the Southern Plains and Southeast. Scientific opportunity knocks. We need to make more progress in understanding the dynamical and physical processes that contributed to past extreme climate outlier events on centennial time scales to help put studies of much more recent and (expected) future extreme climate outlier events into better perspective. Discussion of the possibility of a North Atlantic subtropical cyclone by the end of the weekend or early next week quickly centered on the large variability in run-to-run consistency of the deterministic GFS and ECMWF model runs and a suspicion that the corresponding ensemble forecasts were underdispersive. Discussion of the weekend severe weather threat over the Central U.S. was motivated by the SPC issuance of a high-risk forecast 48 h in advance for parts of the Central U.S. Agreement was widespread with the SPC decision based upon the observational and numerical evidence. A spirited discussion ensued about whether the severe weather threat would be greatest in eastern NE in the warm sector to the southeast of a deepening northeast-moving surface cyclone or southern Kansas and northern OK along the dry line in an environment of increasing shear and CAPE. The discussion was "hijacked" by the late afternoon supercell and tornado that was approaching Norman. No Fri map discussion next week because half the department will be at the AMS Hurricane/Tropical Meteorology Conference in JAX. The students will run the last Fri map discussion of the semester the following week since the subsequent Fri will feature undergraduate research presentations. Off to the airport…. Lance