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02/21/2019, 3:07 pm EST

Daily Feature: Long-lead Forecasts

NOAA Long-lead forecasts March 2019 Outlook Fig. 1-2: The NOAA/CPC March 2019 temperature and precipitation probability outlook. Comment: The polar vortex-inspired cold and supporting snow lingers into March central continent. Warm SSTA southwest of California and east of the U.S. East Coast support warm upper ridging for Southern California and the Atlantic States. The East is wet ahead of the mean trough position anchored over the Central U.S. Spring (MAR/APR/MAY) Outlook Fig. 3-4: The NOAA/CPC MAR/APR/MAY2019 temperature and precipitation probability outlook. Comment: NOAA is convinced an El Nino climate emerges during spring supporting the wet Southern U.S. climate forecast. Each coast is warmer than normal as supported by projected warming SSTA off each coast. Summer (JUN/JUL/AUG) Outlook Fig. 5-6: The NOAA/CPC JUN/JUL/AUG 2019 temperature and precipitation probability outlook. Comment: NOAA continues to maintain a wet climate pattern in the Mid-Atlantic States for summertime. Already wet soil moisture coupled with additional wet climate maintains high flood risk.  The Northwest is dry. Most of the U.S. is warm as supported by projected warm SSTA off each coast and optimum climate normal. Wet soils suppresses heat risk in the Great Plains. Climate Impact Company will issue the constructed analog season 1-3 ahead forecast this afternoon.  
02/06/2019, 11:05 am EST

Daily feature: MJO Shift & Warming Atlantic

Discussion: ALL models indicate a ROBUST Madden Julian oscillation phase_8 in 10 days (and beyond). Represented is an eastward shift of tropical convection from the East Pacific, across the Atlantic and into tropical Africa. During these transitions a following middle latitude trough shifts across the Eastern U.S. supporting a cold (and generally dry) climate pattern. Currently, emphasis is on very cold weather in the West and Central U.S. There is (climate) support for this cold to shift into the East in mid-February. The lower risk mega-clusters identify the East U.S. trough. Bottom line? Risk of colder change mid-February in the high demand energy zone of the Northeast Corridor. Unusual is warming of the North Atlantic basin during February. Normally, the tendency is for cooling (based on seasonality). A similar change occurred early in 2005 especially in the Atlantic tropics. The warming in the tropics is occurring now although not as robust as 2005. Being watched here is pre-tropical season warming of the North Atlantic basin – similar to 2005 – and historically unusual for February. In 2005 a total of 28 tropical cyclones and 15 hurricanes emerged. That’s the (2019 concern). Fig. 1: A robust MJO shifts to phase_8 in 10+ days favoring a cold shift into the East U.S. Fig. 2: Unusual warming (for February) of the North Atlantic basin.
02/03/2019, 3:22 pm EST

Daily feature: How the spring forecast was made

Methodology for generating the U.S. spring forecast Climate discussion: Springtime is typically the most difficult climate forecast as the transition from cold to warm season is usually volatile and changeable. Climate signals such as ENSO are also frequently in transition contributing to forecast uncertainty. Spring 2019 will contain these uncertainties. As always, we begin with ENSO to generate a climate forecast. Analogs are taken from the past ~20 years due to the strong influence on climate for all seasons by the constricting polar ice cap caused by increased CO2 emissions (Fig. 1). From the past 20 years there are 5 ENSO analogs which show a neutral to La Nina signature 1 year ago transitioning to weak El Nino the following winter and similar to the 2018-19 ENSO regime (Fig. 2). In 4 of these analog years ENSO transitioned to neutral phase or La Nina. In one analog year El Nino re-emerged and intensified. Dynamic models are mostly in favor of El Nino in 2019 despite short-term signs of weakening to neutral phase. Additional warming of the equatorial Pacific subsurface near the Dateline now is recognized as fuel for a potential new effort to generate El Nino later this spring. Therefore the forecast is based on a consensus of analogs which indicate neutral to weak El Nino during spring. The MAR/APR/MAY 500 MB anomaly pattern produced by the analogs has similarities to the NCEP CFS V2 model (Fig. 3-4). Most important is agreement on emergence of an upper ridge pattern in central North America. The analog is stronger with an upper trough south of Greenland while the CFS V2 is weaker. The analog and CFS V2 are in agreement on a ridge pattern over Europe. The least confident portion of the projected 500 MB anomaly pattern is the (CFS V2) upper trough over Alaska to Siberia. If this trough is weaker, the North Atlantic trough and Europe ridge will be stronger. The forecast in this report combines persistence (previous outlooks) with the analog forecast and certainly considers the CFS V2 output. Forecast highlights include Fig. 1: The 1953-2018 arctic sea ice extent identifies significant constriction the past 20 years due to CO2 emissions. The influence on climate is sufficiently evident to limit selection of ENSO analogs to the past 20 years. Fig. 2: The ENSO analog years selected from the past 2 decades in which La Nina transitioned top weak El Nino and what followed.   Fig. 3-4: The 500 MB anomalies for meteorological spring generated by the analog years compared to the NCEP CFS V2 forecast model have similarities but vary on intensity.