...CLIMATOLOGY...

IN SPITE OF THE WETNESS, WE HAD A RARE COMBINATION OF BOTH AN 
UNSEASONABLY WARM APRIL AND MAY IN PHILADELPHIA THIS SPRING. SINCE 
1872, THIS COMBINATION HAS OCCURRED ONLY EIGHTEEN TIMES, BUT SIX 
TIMES SINCE 1990. BY DEFINITION UNSEASONABLY COOL/NORMAL/ 
UNSEASONABLY WARM MONTHS ARE DIVIDED INTO THIRDS.  THE FOLLOWING 
ARE TEMPERATURES AND PRECIPITATION THAT OCCURRED IN PHILADELPHIA 
DURING THE ENSUING SUMMERS. WE TRIED TO FOLLOW THE EXPECTED 
ENSO TREND TOWARD EL NINO CONDITIONS. WE DID NOT INCLUDE YEARS THAT 
TRENDED TOWARD LA NINA IN SUMMER OR WERE FAR REMOVED  
FROM ENSO NEUTRAL CONDITIONS DURING THE PREVIOUS WINTER. CURRENT 
EXPECTATIONS ARE FOR THE MAIN ENSO REGION KNOWN AS NINO3.4 IN THE 
EASTERN EASTERN PACIFIC TO HAVE ENSO NEUTRAL CONDITIONS FOR THIS 
UPCOMING SUMMER. HERE ARE THE FAB FIVE.
 

YEAR       JUNE AVG   JULY AVG  AUGUST AVG  SUMMER AVG  SUMMER PCPN 
1896          70.4       77.6       76.6        74.9        7.80 
1993          74.4       81.4       78.9        78.2        8.68
2001          75.2       75.4       79.9        76.8        8.20
2004          71.8       76.3       75.0        74.4       16.65
2006          72.8       79.5       77.7        76.7       16.15

          
AVG           72.9       78.0       77.6        76.2       11.50     
1971-2000 NML 72.3       77.6       76.3        75.4       11.50


ON A SEPARATE NOTE A FINAL CONDITIONAL TEMPERATURE FORECAST FOR 
PHILADELPHIA INTERNATIONAL AIRPORT BASED ON THE ENSO STATE, WHEN THE 
FIRST HEAT WAVE OF THE SEASON OCCURS AND THE MEAN APRIL MINIMUM 
TEMPERATURE CAN BE FOUND AT OUR WEB SITE AT:
WWW.ERH.NOAA.GOV/PHI/REPORTS/SUMMER09FINAL.PDF.  ITS ALL LOWER 
CASED LETTERS EXCEPT FOR THE LETTERS S IN SUMMER AND F IN FINAL.

THE OFFICIAL CPC OUTLOOK FOR THE SUMMER IS FOR A GREATER CHANCE OF 
IT BEING WARMER THAN COOLER THAN NORMAL.