THE MAINE CLIMATE

Newsletter of the Maine State Climate Office
Institute for Quaternary and Climate Studies, University of Maine


Volume 2                                           June 2002                                                       Number 6

Introduction

As we head into summer, we should be optimistic about water conditions around the state.  The precipitation that we have received so far this year has brought about half of the state out of drought conditions and into abnormally dry conditions [see the Drought Monitor figure for 4 June below (Figure 1) as available at http://drought.unl.edu/dm].  The part of the state still considered to be in moderate drought conditions is the central to western and southwestern parts of the state.  A major reason that this part of the state remains in drought conditions is the very slow recovery of water wells.  For example, the USGS well at Sanford has remained at near record low levels through much of this spring.  Although we are optimistic about present water conditions, we need to remain cautious.  We are now in the part of the year when water systems run a natural deficit.  Evaporation and transpiration by plants surpass precipitation in an average year, thus surface water and ground water systems naturally become lower during the summer.  This does not include the additional consumption and usage by humans, which further lower water systems.  We can only hope that the summer does not get very warm and dry.  The outlook for the summer is presented below.

June Climate in Maine

June marks the beginning of solar summer as this year the summer solstice occurs at 9:24 EST (1424 hrs, Mean Greenwich Time or UTC) on the 21st.  This marks the maximum of solar radiation reaching the earthÕs surface, although the impact of that increased insolation is not felt until mid-July when temperatures reach their annual peak.  Nevertheless, temperatures across the state generally will peak in the 70s°F.  Only Caribou and Portland see average maximum temperatures in the 60s, but that is only in the first part of the month.  The amount of daylight in Maine on 21 June is around 15.2 hours, which adds to the increasing temperatures throughout the month.  With the increased heating on land, sea breezes become much more prevalent along coastal areas.  This leads to lower temperatures along coastal areas (as in Portland, see Table 1) and a greater occurrence of fog.

A second important aspect of JuneÕs climate in Maine is the decreasing influence of cyclonic (or storm) activity.  The jet stream and the polar front have been gradually moving to the north since January.  On average, it is located just south of New England by the beginning of summer, meaning that there is a greater probability of it being north of Maine at any given time during the month.  Storms will have a tendency to move north through Canada, thus lessening the impact on Maine.  The trailing cold front, however, still may produce showers as it crosses the state.  Coastal storms also may occur in June, but their frequency is much lower than in the previous months, and they become rare by the end of June.  Although the official start of the hurricane season in the Atlantic Basin is 1 June, a tropical storm/hurricane rarely will reach Maine during this month.  The combination of these factors mean that the most frequent method of receiving precipitation in June is through convective storms resulting from day time heating and the subsequent destabilization of air parcels close to the surface.  This rising air eventually may produce scattered showers or thunderstorms, and thus a more erratic pattern for June precipitation compared to that from the more-frequent well-developed storm systems of the winter and spring seasons.  This is one reason why some parts of the state may receive lower than average amounts of precipitation during June, but others receive amounts closer to average.

FIGURE 1

TABLE 1


MEAN CLIMATIC CONDITIONS ACROSS THE STATE IN APRIL

Date                                                     Caribou           Bangor            Augusta            Portland

Temperature (°F)

1 June

            Daily High                              68                    71                    72                    69
            Daily Low                               46                    49                    50                    49
            Mean                                       57                    60                    61                    59

15 June

            Daily High                              72                    74                    74                    73
            Daily Low                               50                    53                    54                    53
            Mean                                       61                    64                    64                    63

30 June

            Daily High                              75                    77                    78                    76
            Daily Low                               53                    57                    58                    56
            Mean                                       64                    67                    68                    66

Monthly Summary

            Mean Temperature (°F)           60.8                 63.9                 64.4                 62.9
            Heating Degree Days              159                  79                    80                    116
            Cooling Degree Days              39                    45                    60                    51
            Mean Precipitation (in.)           3.31                 3.41                 3.58                 3.28


Means based on 30-year period from 1971 to 2000.  Heating and Cooling Degree Days from a base of 65°F

Looking Ahead

According to the Climate Prediction Center (NOAA) there is a greater than 33% chance over the next few weeks of June of receiving greater than average precipitation in the eastern half of the state.  This means a less than 33% chance of below average precipitation and about a 33% chance of average precipitation amounts.  The western half is under climatological conditions (that is, equal changes of above, at , below average).  However, this trend will be short-lived as the prognosis for the rest of the summer (June, July, August) is for climatological conditions to prevail.  This means an equal chance of above, at, or below average precipitation amounts.  Temperature outlooks are for climatological conditions, as well.  The El Nino is still forming in the Pacific Ocean, but it still is only be forecasted as a weak to maybe moderate event.  Such conditions would mean that we might have winter temperatures warmer than average, but the weaker the event, the less chance of that occurring.  As 1 June is the beginning of the hurricane season, forecasts for the number of tropical systems that may form in the Atlantic Basin are out.  Both Dr. William Gray (Colorado State University) and NOAA are forecasting an average or slightly above average season for tropical systems.  This is line with a weak El Ni–o, as strong El Ni–o events will inhibit tropical system formation.  An average to slightly above average tropical system season means the possibility of 9-13 storms forming this year.  Of those, 2-3 have are likely to become major hurricanes, that is Category 3 or better.  HOWEVER, it is important to realize that there is NO correlation between the number of tropical systems in the Atlantic and the number that make landfall.  On the other hand, one could say that we are due for a landfall hurricane here in New England because we average one every five years since 1886.  We have not had one since 1996, when Hurricane Isidore brushed outer Cape Cod.

Past June Events

6-7 June 1816:  It is hard not to talk about the snows of 1816 when discussing weather and climatic events in the month of June.  The cold and snow of early June 1816 was just the beginning of the ÒYear Without a SummerÓ following the eruption of Tambora in April 1815.

14 June 1992:  Although not a major event, the trace of snow that fell in Bangor on this day marks the latest official trace of snow recorded in Bangor both at the airport (since 1953) and in other parts of town (1925-52).

18 June 1875:  A late-season coastal storm brought 57 mph winds to Eastport.  The number of coastal storms decreases through the spring with limited numbers occurring in June.

May 2002 in Maine

For the most part, May was a cool, damp month.  It was only in the latter week that high temperatures consistently reached into the 70s (Figure 2a).  Parts of mid-month only had daytime highs in the 50s.  Lows dropped to freezing or below in most of the state around the 20th (Figure 2b).  In fact, Caribou had 9 days at freezing or below.  It sure did not feel like spring for most of the month.  Further evidence of the cool month comes from daily averages in Bangor (Figure 2c).  Only 8 days were at or above the 30-year average.  Mid-May felt more like mid-April to many of us.  The snow that fell late in Caribou at this time (Figure 3a) further emphasizes that winter conditions can appear in May just about anywhere in the state!  Interestingly, the pattern of precipitation amounts changed slightly from the first few months of the year.  Areas in the central part of the state, like Bangor, were generally receiving above average precipitation in most months, while the southwestern part of the state was generally below average.  The north was close to average.  In May, Portland received 4.43 inches, which is 0.51 inches above average with Caribou receiving 3.97 inches, 0.70 inches above average.  Bangor only had 2.51 inches this month, which is almost an inch (0.89 in.) below average.  Similarly, Bill Larrabee reported 2.63 inches at Sebec Lake (1 inch below average), but Larry Dwight reported 5.44 inches in Kennebunkport.  The dampness of the month also is reflected in the number of days without precipitation.  There were not too may days in a row without rain or snow.  The 4 days beginning on the 22nd in Bangor (Figure 3b) without precipitation was the longest Òprecip-freeÓ period for these three stations.


FIGURE 2a

FIGURE 2b

FIGURE 2c

FIGURE 3a

Note:  Precipitation for Caribou includes 2.7 inches of snow on the 14th and 0.4 inches of snow on the 15th.  Snow data were missing for Bangor on these two days.

FIGURE 3b

Note: Precipitation plots display "Trace" as 0.01 inches.

ALL DATA SHOWN ON PLOTS ARE UNOFFICIAL


Contact Information for the Maine State Climate Office

Dr. Gregory A. Zielinski
Maine State Climatologist (http://www.umaine.edu/maineclimate)
Institute of Quaternary and Climate Studies (http://www.ume.maine.edu/iceage)
University of Maine
Orono, ME 04469-5790

207-581-3441

gzielinski@maine.edu