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11/28/2018, 2:32 pm EST

Europe Season 1-3 Ahead Outlook

Mild Winter, drought returns/expands eastward for summer 2019 Executive Summary: The drought condition across Europe eases (but does not end) during the winter 2018-19 season. Dry conditions re-emerge central and southwest Europe next spring and expand (and intensify) in Southeast Europe to the Black Sea region next summer. Western Europe observes a stormy winter while Northwest/West Russia also observe above normal precipitation during the cold season. Winter 2018-19 and spring 2019 are milder than normal due to influences of the projected NAO pattern enhanced by strengthening El Nino. Eastern Europe to Western Russia is hot next summer season. Climate discussion:  An intense drought is affecting most of Europe. Soil moisture conditions are either in “warning” or “high stress” status according to the European Drought Observatory (EDO) for the region and most profoundly in France and Germany (Fig. 1).  The drought has affected river levels which have reached historical lows through Central Europe including the Rhine River for the second time in 30 days. The drought was caused by a semi-permanent high pressure ridge cresting over Europe (Fig. 2) for much of 2018. The positioning of the upper ridge is representative of the positive phase of the North Atlantic oscillation (+NAO). During 2018 the strongest +NAO on record has occurred. Does the upper ridge pattern break down for the 2018-19 cold season? Will drought continue into 2019 and regain strength during the 2019 warm season? Fig. 1: According to the Europe Drought Observatory soil moisture conditions for the first third of November are identified. Fig. 2: A semi-permanent high pressure ridge across Europe in 2018 has caused the intense historic drought. The leading indicators of climate across Europe for winter 2018-19 are the NAO, snow cover pattern and risk of arctic air arrival spreading westward from Russia. Governing these factors are extent of open water north of Europe influencing high latitude high pressure blocking patterns and long distance influence by El Nino on the North Atlantic maritime contribution to the Europe climate. Based on analogs the likelihood of a strong +NAO observed in 2018 continuing during the 2018-19 winter season is above average. The analogs are 2013-14, 1999-2000, 1994-95, 1992-93, 1990-91 and 1989-90. However, the analogs are in the face of optimum climate normal (OCN) which is the short-term (10-year or 15-year) climatology. OCN is considered due to the persistence of high latitude blocking during the winter season of the past 10-15 years fueled by the warming of the atmosphere of open water north of Europe. El Nino is developing. While El Nino has limited influence on European winter climate unless intensity is moderate or greater there are certainly downstream effects from the North America climate. El Nino 2018-19 is forecast to produce moderate intensity and influence on global climate well into 2019 (Fig. 3). Reasonable is anticipation of at least some influence of the warm tropical East Pacific on climate patterns affecting Europe. Fig. 3: The Bureau of Meteorology/Australia Nino34 SSTA forecast through June of 2018 reveals moderate intensity El Nino lasting into next summer. The NAO analog years plus OCN help to forecast the position of the polar vortex for the winter season. This consideration is paramount to the climate forecast. The ENSO contribution to the forecast is second-most important therefore moderate El Nino episodes occurring during the NAO analog years and/or OCN (only) are considered. Moderate El Nino episodes for winter-to-spring occurring during the past 30 years with the NAO analogs and/or OCN include 2014-15, 2009-10, 2006-07, 2004-05 and 1994-95. Only the 2014-15 El Nino carried through the following year (as El Nino 2018-19 may) and is therefore considered more heavily in the extended analog forecast. Each of the El Nino analogs are valid due to their inclusion within OCN plus the 1994-95 NAO analog. Based on the analog strategy the 500 MB anomaly forecast across Europe for DEC/JAN/FEB 2018-19 indicates a robust stormy trough north of U.K. with a downstream upper ridge across Southeast Europe/Southwest Russia (Fig. 4). The NAO analog years maintain +NAO while the ENSO influence across the North Atlantic pushes the +NAO upper trough near Greenland eastward toward Europe. Fig. 4: The 500 MB anomaly forecast across Europe for winter 2018-19 based on NAO and ENSO analog years. Outlooks: The season 1-3 ahead climate outlooks for Europe include winter 2018-19 to summer 2019 compared to the previous forecast for temperature and precipitation anomalies. DEC/JAN/FEB 2018-19: The meteorological winter 2018-19 outlook for Europe is warmer-than-normal including Western Russia. A persistent upper trough and associated storm track across the North Atlantic and into Western Europe propels a persistent fetch of milder than normal maritime influence across Europe. The upper air pattern also inspires a persistent mild maritime influence on Northern Europe into Northwest Russia from the open (ice free) waters of the Norwegian Sea. Arctic air moving west from Russia is possible during late winter. The precipitation pattern is above normal across Western Europe. Precipitation amount across the central drought zone is mostly near normal. The forecast is adjusted warmer from the previous outlook. Fig. 5-8: Climate Impact Company DEC/JAN/FEB 2018-19 temperature and precipitation anomaly outlook. The previous forecast is below. MAR/APR/MAY 2019: A warmer than normal climate remains in-place across much of Europe and especially Western Russia next spring. Southern Europe is normally mild. The precipitation forecast indicates marginally dry conditions across central and southwest Europe. Northern and eastern portions of Europe are marginally wetter than normal. Northwest Russia and the Black Sea region are marginally wetter than normal during spring 2019. The forecast is similar to the previous outlook. Fig. 9-13: Climate Impact Company MAR/APR/MAY 2019 temperature and precipitation anomaly outlook. The previous forecast is below. JUN/JUL/AUG 2019: Summer 2019 returns hot and drought risk to Southeast Europe to Ukraine/Black Sea region where a subtropical high pressure system develops and amplifies for mid-summer. More dryness across Central Europe is likely. Fig. 14-15: The preliminary Climate Impact Company JUN/JUL/AUG 2019 temperature and precipitation anomaly outlook.