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07/22/2019, 7:56 pm EDT

U.S. Week 2-4 Outlook

Highlight: Northern States are warmer-than-normal in August. Charts of the day: Dry soil TREND foreshadowed heat wave. Discussion: The much drier soil moisture trend during mid-summer across much of the East U.S. foreshadowed the heat wave that would follow. Week 2 Ahead: July 28-August 3, 2019 Comment: The forecast trends warmer in the Northwest and remains warm across much of the West except cooler in the Northwest. The western U.S. is dry while marginally wet weather stretches across the Interior East. Week 3 Ahead: August 4-10, 2019 Comment: The outlook stays dry in the Midwest to Texas while the Southeast States are wetter than normal. Anomalous warmth spreads across the northern half of the nation from coast-to-coast. Week 4 Ahead: August 11-17, 2019 Comment: The week 4 forecast is made with low confidence. Of interest is a projected wet pattern in the Gulf region associated with a possible tropical cyclone. North of that weather risk warmth is dominant.
07/22/2019, 2:11 pm EDT

Weekly ENSO Diagnostics Report

Looking Like an El Nino Modoki Discussion: The ever-changing ENSO regime has yet again has a new look. Recent weeks of cooling in the eastern equatorial Pacific have defeated the 2018-19 weak (conventional) El Nino. However, leftover warmth at the surface (Fig. 1) and subsurface (Fig. 2) near the Dateline indicate an El Nino Modoki may be developing (Fig. 3). The Nino SSTA regions are each below the El Nino threshold except Nino4 (central Pacific) which remains robustly in El Nino territory (Fig. 4). When was the last late (northern hemisphere) summer El Nino Modoki? Since the ENSO/PDO and AMO cycle change in the mid-to-late 1990’s an El Nino Modoki has been present during August in 2002 and 2004. In both cases the El Nino Modoki strengthened the remainder of the year. Interestingly, the 2002/2004 analog upper air pattern for August features a Central U.S. trough and ridge pattern on each coast similar to analogs produced for August when atmospheric angular momentum (AAM) becomes negative (mentioned in yesterday’s notes). The largescale climate pattern for August appears to be heading for a wet solution reaching from the Gulf States to the Corn Belt. Summary: Conventional El Nino has ended. However, the warmth associated with the weak El Nino of 2018-19 remains in-place both at the surface and subsurface near the Dateline in the equatorial Pacific. The trend of warming near the Dateline while the eastern equatorial Pacific cools remains in-place. A weak El Nino Modoki may be forming. Fig. 1: Global SSTA observations for July 20, 2019 reveal an El Nino Modoki look in the equatorial Pacific Ocean. Fig. 2: The El Nino Modoki is supported by warmth in the subsurface near the Dateline. Fig. 3: An El Nino Modoki has generated in recent weeks. Fig. 4: The Nino SSTA regions have trended cooler to beneath El Nino thresholds except the Nino4 region which is near the Dateline.
07/22/2019, 9:59 am EDT

U.S. Medium-range Outlook

Highlight: Warmer Medium-range forecasts. Charts of the Day: Heat risk returns to California. Discussion: Hotter forecasts are indicated for California for late July/early August. Sacramento has a chance to reach 100 each of the next 15 days. Medium-range 6-10 Day Forecast Valid July 27-31, 2019 Medium-range 11-15 Day Forecast Valid August 1-5, 2019 Discussion: Suppressed heat due to shower activity becomes established over the Southeast U.S. Elsewhere the forecast trends warmer in the West and Northeast U.S. with slight risk of excessive heat. Extended-range 16-20 Day Forecast Valid August 6-10, 2019 Discussion: A very warm and humid pattern is projected across the U.S. Corn Belt. Warmth also lingers in the West. A cool outbreak from Canada emerges. The GFS OP days 6-10/11-15 %Normal Rainfall Forecast Discussion: The GFS ENS indicates wet weather over the Great Lakes in the 6-10 day period while the majority of the remainder of the U.S. is dry. In the 11-15 day period there is risk of a thundery pattern across the Southeast U.S. (and California).  
07/22/2019, 5:39 am EDT

Early AG Market Wire

Mega-clusters suggest a drier and warmer U.S. Corn Belt forecast Discussion: Forecast trend for the medium-range across the U.S. is a little different this morning. The jet stream to is now forecast to stretch across the U.S./Canada border featuring a showery upper trough in the Great Lakes region days 6-10 and a far-enough north shift into Southeast Canada days 11-15 to support tropical rains in the Gulf/Southeast U.S. days 11-15 (Fig. 1-2). The U.S. Corn Belt trends drier and warmer! Yesterday the forecast discussion mentioned the Mexican Monsoon developing with a spill-over of Interior West wet weather into the western Corn Belt in August indicated by NOAA/CPC climate forecasts. An alternative approach is wet weather shifting north toward the Corn Belt caused by tropical weather in the Gulf of Mexico. The second pattern described may be developing for early August. Fig. 1-2: Most likely precipitation scenario based on mega-cluster forecast for the medium-range across the U.S. Change in the Global Atmospheric Angular Momentum Pattern Fig. 3: Global atmospheric angular momentum index pattern change. Discussion: Global atmospheric angular momentum (GLAAM) is a measure of how fast the atmosphere is spinning relative to the earth’s rotation. The 15-day GLAAM forecast (Fig. 3) indicates a recent pattern change to the negative phase has occurred and will intensify into August. During the negative phase of GLAAM the atmosphere moves more slowly relative to the earth’s rotation causing mid-latitude jet streams to produce higher amplitude ridge and trough patterns (which can cause climate extremes as observed with the heat wave of the past few days in the U.S. and in Europe this week). Negative GLAAM is common when La Nina is present and offers more evidence that the weak El Nino pattern of 2018-19 has ended. The August analog years for Negative GLAAM during neutral ENSO since 2000 are 2005 and 2012 which were active North Atlantic tropical cyclone years. Hot Europe ridge to last 7-10 days Fig. 4-6: Most likely upper air pattern across Europe this week and in the medium-range forecast by mega-cluster model. Discussion: The next heat wave of note is across Europe this week as supported by the amplified upper ridge pattern offered by the mega-cluster most-favored solution (Fig. 4). Temperatures surge to 100-105 in Spain and France. There are questions as to how long the supporting upper ridge lasts. The mega-cluster favors more warmth days 6-10 although less extreme with excessive heat in Spain, France and Germany slowly easing (Fig. 5). In the 11-15 day period the upper ridge is gone and the semi-permanent cool trough in Western Russia returns to prominence (Fig. 6). Black Sea showers this week but drier next week Fig. 7-8: GFS ENS indicates wet weather in Southwest Russia the next 2 weeks although Black Sea region turns drier next week. Discussion: While Europe basks beneath a hot upper ridge pattern this week a downstream trough brings rain to the Black Sea region with showers extending across Southwest Russia (Fig. 7). The focus returns to the persistent Western Russia upper trough days 8-14 increasing wet weather risk while the Black Sea region turns drier (Fig. 8).