OVERVIEW:  The month of May projections were maintained this week for a near to slightly below average (-0.0°F to -2.0°F) temperature departure for the month as a whole. Cooler than average temperatures during the first half of the month were largely offset by the very hot temperatures near mid-month, but cooler risks have followed most days since Memorial Day weekend. The exception within our region is the heat island areas such as Philadelphia and Newark, where monthly temperatures are running +1.0°F to +2.0°F currently. Projections for the month of June were maintained this week for a near average (-0.5°F to -0.5°F) temperature departure. July projections were introduced this week for another near average (-0.5°F to -0.5°F) temperature departure using long term climate guidance and global observation trends.

• Since the mid-month ridging which resulted in well above average and summer temperatures in the 90s, very cool temperatures followed over the Memorial Day holiday weekend and cooler risks are expected through the end of May and early June. This will allow most areas to finish on the slightly cooler side of average for the month, with the heat island areas being the exception. June is shaping up to lean slightly warmer than average during the first half of the month, and generally near average thereafter. Although there can be shorter term temperature fluctuations above or below average, the larger picture of June is more likely to follow the early Summer El Niño paradigm.

   

• The Madden-Julian Oscillation (MJO) is currently in phase 7 in the Western Pacific, and is expected to maintain there through the first few days of June. Afterwards, a brief stint in phase 8 is possible before collapsing into the Circle of Death (COD) or NULL phase. This propagation would suggest a general fast-moving pattern with near average temperatures as we transition from ENSO neutral to El Niño.

   

• A composite average of the SST departures in the ENSO regions places it in El Niño territory currently. From west to east across the Pacific, the Niño 4 (west-central Pacific) is currently +1.1°C, and the Niño 3.4 region (east-central Pacific) is currently at +1.0°C. The eastern regions of Niño 3 (east-central Pacific) is currently +1.2°C, and Niño 1+2 region (near the Peruvian coast) is at +2.1°C as of May 27th. The threshold for El Niño begins at +0.5°C as a composite average of the ENSO regions, and although not officially declared by the CPC, it is the expected transition, and an El Niño Summer and Fall will follow.

   

Average high temperatures are currently in the 75-78°F range from north to south across our coverage region, which is about 1-2°F higher than at this point last week. Climatological annual maximum temperatures will be achieved in mid-July. Any above or below average stretches listed in the outlook will be relative to seasonal norms at that time, and it is important to note that cooler/warmer periods will be relative to the time of year we are talking about. For example, the slightly below average temperatures listed for May 30th-June 3rd features highs in the mid 70s, coming at a time when average highs are in the upper 70s to near 80 degrees. Use the average highs/lows chart below providing transparency for what average temperatures are expected to be at each corresponding location through July 15th.

May projections were maintained this week for a near to slightly below average (-0.0°F to -2.0°F) temperature departure for the month as a whole, with the exception across the I-95 heat island locations like Philadelphia and Newark. which will finish slightly above. The projections for the month of June were maintained this week for a near average (-0.5°F to +0.5°F) temperature departure, and July projections were introduced this week for the same near average (-0.5°F to +0.5°F) temperature departure using long term climate guidance and global observation trends.