May 27, 2002
Late-May Drought Update
Dr. David A. Robinson
New Jersey State Climatologist
Rutgers University
Precipitation during May has totaled between just over 3 inches and just over 5 inches. These values are from several tenths of an inch below normal to as much as 1.5” above normal. The driest area of the state has been the coastal counties of Ocean and Monmouth. Hunterdon county is the wettest, with Sussex, Essex and Somerset counties not far behind. North Jersey precipitation is from about 0.5” to 1.5” above average, south Jersey precipitation from several tenths of an inch below average to about 0.5” above.
It is certain that May will be the third consecutive month with above average statewide precipitation. However, March precipitation was only 0.18” above and April only 0.13” above average. Thus, spring 2002 will end on the wet side, though unless the last several days of the month are wet, only somewhere between a half inch and an inch above average. Thus the statistically significant relationship between above average offshore sea surface temperatures in winter and a wet NJ spring, mentioned in the early March drought statement, holds. However there is much more to learn about this association before one can use it confidently as a seasonal forecasting tool.
Speaking of forecasts, the 6 to 10 and 7 to 14 day National Weather Service forecasts issued earlier today call for those periods to be wetter and cooler than normal across the Garden State. The NWS monthly outlook for June gives equal chances to precipitation and temperature being in the lower, middle or upper terciles compared to past Junes. This is also the case for the seasonal outlooks for June-August, and for three-month intervals through the fall. The latter is a change from the extended seasonal outlook issued last month for the fall, which suggested the Middle Atlantic, including NJ, might be on the dry side.
The major question of the day is whether the climatological drought has ended. Three consecutive months of close to or slightly above average precipitation provides increasing evidence that the lengthy dry pattern has broken. This is certainly more significant than, for instance, seeing one very wet month, such as September 1999. However, given that drought like conditions have existed since July 1998, we will have to see what the summer brings and at least remove a bit more of what had been an 18” deficit over the previous year and a half or so to be certain that this drought has ended.