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10/18/2018, 10:48 am EDT

Daily Feature: NOAA/CPC Longlead Climate Forecasts

NOAA Probabilistic Climate Forecasts Discussion: The monthly long-lead probability climate forecasts issued by NOAA/CPC were released this morning. The primary contributor the winter/spring ahead forecast is ENSO. NOAA/CPC continues to forecast El Nino within 2 months but a weak event is expected making traditional El Nino/winter climate relationships less reliably forecast. NOAA/CPC identifies above normal snowfall across eastern Canada into October as a contributor to the late 2018 climate pattern. Fig. 1: The CPC/IRI ENSO probability forecast through MAY/JUN/JUL 2018. November 2018: The warm outlook is STRONGLY biased by warm tropical and non-tropical SSTA in the East Pacific and off the East Coast of the U.S. The wet pattern across the South and East U.S. is caused by approaching El Nino onset. Above normal snow cover across Eastern Canada leading into November will need to retreat for this warm forecast to verify. If the snow cover remains a colder scenario is likely for the Great Lakes to the Mid-South U.S. Fig. 2-3: The November 2018 temperature/precipitation probabilistic climate forecast for the U.S. issued by NOAA/CPC. Meteorological winter (DEC/JAN/FEB 2018-19): The outlook is biased by an El Nino climate and also warm SSTA into the northeast North Pacific. The result is warmer than normal climate across much of the U.S. An upper ridge pattern is favored in the West which leaves the East and particularly the Southeast States susceptible to an occasional cold upper trough. The precipitation forecast is a very typical El Nino amplified wet southern storm track. There are a lot of caveats here. First, warming of the northeast Pacific suggests emergence of the positive phase of the Pacific decadal oscillation. While this could happen there is no sign of this regime change yet. Second, the prediction of weak El Nino may be more related to the possibility of an El Nino episode with most of the East Pacific surface/subsurface ocean warming biased toward the Dateline rather than the northwest coast of South America. The caveats based on the PDO and Modoki-style ENSO potential is less warm Northwest and possibly colder East. Fig. 4-5: The DEC/JAN/FEB 2018-19 temperature/precipitation probabilistic climate forecast for the U.S. issued by NOAA/CPC. Meteorological spring (MAR/APR/MAY 2019): El Nino should linger into next spring. El Nino could be stronger than suggested. The NOAA/CPC outlook maintains an El Nino wet look in the Southeast U.S. while all but the Midwest to New England states is likely warmer than normal. Fig. 6-7: The MAR/APR/MAY 2019 temperature/precipitation probabilistic climate forecast for the U.S. issued by NOAA/CPC. Meteorological summer (JUN/JUL/AUG 2019): The summer 2019 outlook is almost exactly alike to the summer 2018 forecast with anomalous warmth just-about everywhere and wet climate across the Northeast. Fig. 8-9: The JUN/JUL/AUG 2019 temperature/precipitation probabilistic climate forecast for the U.S. issued by NOAA/CPC. Fig. 10: The seasonal drought outlook for the U.S. issued by NOAA/CPC. Seasonal (next 90 days) drought outlook: The NOAA/CPC seasonal drought outlook eliminates drought in the Southwest U.S. while maintaining drought in southern California and across the Great Basin. Drought eases on the Northwest Coast while the Columbia Basin stays dry.
10/15/2018, 2:45 pm EDT

Daily Feature: A Review of 1986-87 El Nino

REVISIT El Nino 1986-87 Discussion: There are two interesting aspects to the current El Nino southern oscillation (ENSO): 1. Lack of commitment on part of surface/subsurface warming of the central/east-central equatorial Pacific Ocean to spread eastward and 2. Basin-wide subsurface anomalous warmth in the equatorial region which is strengthening. Subsurface data was not available for the 1986-87 El Nino but surface characteristics are closely related to 2018. In late 1986 an El Nino Modoki developed in which the bulk of the Pacific warming inspiring El Nino was biased toward the Dateline rather than the northwest coast of South America. Using the Nino12 (northwest coast of South America) and Nino34 (east-central equatorial Pacific) index a comparison of 1986 to 2018 reveals similarities (Fig. 1). In 1987 ENSO transitioned from a Modoki to a top 5 long duration El Nino event (Fig. 2). The long duration intense event was likely caused by abundant subsurface warmth in the tropical oceans similar to 2018.  Proposed is a similar ENSO regime for 2018-19: El Nino Modoki to strong (conventional) El Nino lasting all of 2019. The modern-day climate is different from the 1980’s in that the global oceans are much warmer now and polar ice cap much more constricted. However, a review of global climate as related to the 1986-87 El Nino is worth reviewing for increasingly likely similarities by ENSO to the 2018-19 climate. Fig. 1: The current Nino12/Nino34 SSTA scheme is similar in character to 1986 in that Nino34 is warmer than Nino12 (usually the opposite is true of a developing El Nino). Fig. 2: After an El Nino Modoki onset in late 1986 a more conventional long duration strong El Nino followed in 1987. Given the massive abundance of subsurface ocean heat in 2018 this scenario is possible for 2019. DEC/JAN/FEB 1986-87: El Nino Modoki was present for meteorological winter (summer) in the northern (southern) hemisphere. EXTREME climate in both hemispheres followed. In North America (after a cold utumn in the U.S.) El Nino onset brought a warmer pattern but focused mostly on Canada and only the northern portion of the Great Plains (Fig. 3) and this scenario is possible for winter 2018-19. Note that most of the U.S. is temperate to cooler than normal. The precipitation pattern was drier than typical El Nino for the West Coast (Fig. 4) with typical stormy conditions of an El Nino confined to the Gulf Coast to the coastal Carolinas. Shock cold (and snow) struck Europe and Western Russia during winter 1986-87 (Fig. 5-6). Fig. 3-4: The 1986-87 winter El Nino Modoki brought less rain/snow than conventional El Nino to the West Coast and a limited Southeast U.S. storm track while most of the El Nino warming was in west/south Canada. Fig. 5-6: The 1986-87 winter El Nino Modoki brought SHOCK cold to Europe and Western Russia and a snowy regime to Central Europe. The southern hemisphere meteorological summer 1986-87 observed El Nino Modoki produce an exceptionally dry climate across Brazil – drier than a normal El Nino episode (Fig. 7). The Australian summer was very dry on the East Coast (Fig. 8). Fig. 7-8: The 1986-87 summer El Nino Modoki produced very dry climate across Brazil and eastern Australia. El Nino lingers and strengthens for JUN/JUL/AUG 2019. Leading into summertime the transition from El Nino Modoki to conventional El Nino leaves the Midwest to Mid-South U.S. dry (Fig. 9). In Europe the reverse is true as wet weather defeats a drought repeat (Fig. 10). Fig. 9-10: Following the winter 1986-87 El Nino Modoki a conventional El Nino developed for 1987. The spring-into-summer precipitation pattern was dry in the East-central U.S. and across Europe. Summary: A particular type of El Nino is ahead. El Nino onset arrives by December 1st. Initially, El Nino is biased by most of the attendant warming near or east of the Dateline. This affect lasts through most of DEC/JAN/FEB 2018-19. The influences on climate are… Failure of expected rains into California. With the exception of the northern Plains typical El Nino warming fails across the U.S. The storm track is most evident in the Gulf States to the Carolinas. Implications for Europe and Western Russia is potential shock cold. A drought develops and widens in Brazil. Eastern Australia drought is intense. El Nino Modoki transitions to a conventional El Nino in 2019 and lasts ALL year. A few implications include… Potential drought for the Midwest/Mid-South U.S. leading into summer. No Europe drought as rains ease that risk. Very limited tropical cyclone activity in the North Atlantic for 2019.
10/14/2018, 12:21 pm EDT

Daily Feature: Quebec Snowcover Increase Leads to East U.S. Chill

Deepening Canadian Snows Support a Cooler East U.S. Climate Ahead Discussion: After a long duration warmer-than-normal climate (sometimes record warm) across the East/Southeast U.S. a weather pattern change is on the way. Extremes tend to breed opposing extremes in the modern climate. Unusually deep snow cover is expected to evolve in eastern Canada and into the New England mountain areas the next 2 weeks providing a cold air source region which will frequently surge southward into the eastern states. Temperatures will average a few degrees below normal this week in the Northeast, 2-5F below normal in the East in the 6-10 day period and 3-7F below normal days 11-15. The steadily increasing chill will FEEL all that much (more) chilly because of the super warm start to the autumn season. Fig. 1: The GFS Ensemble (model) forecasts deep snows across Central and East Canada most impressive over Quebec. Deepening snow cover provides a cold air source region for the East U.S. Fig. 2: Snow cover is well ahead of schedule across Central and East Canada plus parts of the West-Central U.S. Fig. 3-5: Climate Impact Company day 1-5, day 6-10 and day 11-15 temperature anomaly forecasts identify a cooler pattern change for the East.
10/12/2018, 4:07 am EDT

A Warm Ocean Leads to a Big Year for Northern Hemisphere Tropical Cyclones

Big Year for Northern Hemisphere Tropical Cyclones North Atlantic Overachieves Fig. 1: Accumulated Cyclone Index for each northern hemisphere ocean basin and total ACE for the northern hemisphere through October 11, 2018 is indicated. Data is provided by the Colorado State University Tropical Meteorology Project. Discussion: A whopping 165% of normal accumulated cyclone energy (ACE) has been observed in 2018 through October 11 across the ocean basins of the northern hemisphere. The ACE index is calculated by squaring the maximum sustained surface wind of the tropical system every 6 hours and totaling that value for a given storm and for each individual storm for a season. ACE index more accurately measures the intensity of a given season versus just the number of storms and hurricanes. Hurricane expert Phil Klotzbach of the Colorado State University Tropical Cyclone Project provides real-time data used in this report. You can find the data at the link below… http://tropical.atmos.colostate.edu/Realtime/ In 2018 the most active basin has been the northeast North Pacific (east of the Dateline) where an incredible 247% of normal ACE has been observed. In the northeast North Pacific a total of 19 tropical cyclones of which 12 have become hurricanes and 9 intense hurricanes are values which are above normal climatology. However, the number of days in which a hurricane and intense hurricane have been present are stunning…64.5 hurricane days (27 is normal) and 32.75 intense hurricane days (8.1 is normal). These northeast North Pacific values are the leading contributor to the well above normal northern hemisphere activity. The North Atlantic has over-achieved this year. Seasonal forecasts indicated near to below normal activity anticipating an inhibiting El Nino arrival. But El Nino is delayed until after the tropical cyclone season which allowed the North Atlantic tropics to flourish producing 14 tropical cyclones of which 7 became hurricanes with 2 intense hurricanes (both smashing into the U.S.). The North Atlantic ACE index is 130% of normal. Seasonal forecasts were in the 50% range. The northwest North Pacific (east of the Dateline) produced 25 tropical cyclones of which 13 became typhoons and 8 intense typhoons. Each value is slightly above climatology. Once again the number of days the typhoons and intense typhoons compared to normal drove the buoyant seasonal ACE index for this basin. The north Indian Ocean was 247% more active than normal. The above normal tropical cyclone activity is caused primarily due to the above normal ocean surface temperatures and upper ocean heat content. The most dramatic warmth is located in the central and eastern tropical Pacific increasing recently as an El Nino episode is organizing. The strongest warming in the tropical Pacific Ocean has been toward the Dateline providing an explanation for record number of tropical cyclone events in the Hawaiian Islands in 2018. Entering the tropical cyclone season the tropical North Atlantic was unusually cool. But dramatic warming evolved well into the tropical cyclone season allowing the North Atlantic to produce an above normal seasonal ACE index. The middle latitudes of the North Pacific and North Atlantic were much warmer than normal allowing storms to be stronger than normal north of the tropics. Through August 2018 the global oceans were 5th warmest in the historical record. Ranking in the top 5 has been common in this decade. Fig. 2: The global ocean temperature anomalies for the past 90 days in which the bulk of northern hemisphere tropical cyclone activity occurred is provided by NCDC/PSD. Note the strongest warmth in the most active basin…the North Pacific east of the Dateline. Fig. 3: Current global ocean temperature anomalies identify the warming trend well into the tropical cyclone season fueling above normal tropical cyclone activity for each basin in the northern hemisphere.