In 2008, the National Weather Service (NWS) changed the definition of the start of the Southwest monsoon from a variable date based on locally measured conditions to a fixed date of June 15 (and a fixed end date of Sept 30). Prior to 2008, the flexible start date reflected the seasonal progression of the monsoon, with a considerable temporal gradient across the region (Fig. 1). (read more)
Oceanic and atmospheric conditions remained ENSO-neutral over the last month (Figs. 1-2) and most ENSO forecasts and outlooks reflect that. On July 10, the Japanese Meteorological Agency (JMA) identified neutral conditions in oceanic and atmospheric indicators, but with indications of warming oceanic temperatures in the coming months. The agency forecast equal chances (50 percent) of either ENSO-neutral or El Niño by fall 2018. (read more)
Precipitation and Temperature: Precipitation in June ranged from record driest to much-above average (Fig. 1a); the wetter-than-average areas were those impacted by the remnants of Hurricane Bud in mid-June. June is typically dry, barring an early onset of monsoon activity, so any pre-monsoon precipitation will boost percentile rankings. June temperatures were warmer than average across all of Arizona and New Mexico (Fig. 1b), including record-warm conditions in eastern Arizona and central New Mexico. (read more)
