SUMMER 2002 OUTLOOK FOR SOUTHEAST LOWER MICHIGAN

Written by: William R. Deedler, Weather Historian

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AS WE MOVE INTO THE SUMMER MONTHS, LET'S TAKE A LOOK AT SOME PREVIOUS SUMMERS THAT CONTAINED SOME SIMILAR CLIMATE CHARACTERISTICS AND ENVIRONMENTAL CONDITIONS. LATEST INDICATIONS ARE A WEAK EL NINO WILL CONTINUE TO EVOLVE AS THE SUMMER UNFOLDS BUT ITS INFLUENCE ON THE SUMMER PATTERN SHOULD STILL BE LIMITED.

IN RESEARCHING FOR THIS OUTLOOK, SEVERAL OF THE SUMMERS THAT FOLLOWED THE WINTER SEASONS PREVIOUSLY STUDIED FOR THE WINTER 2001-02 OUTLOOK WERE USED. IN ADDITION, THREE OTHER NEUTRAL TO WEAK EL NINO SUMMERS, 1953, 1957 AND 1997 WERE INCLUDED. THE MAJORITY OF SUMMER SEASONS IN THE STUDY CONTAINED SIMILAR EVOLVING EL NINO TIMINGS AND SOLAR ACTIVITY, BUT NOT ALL. FINALLY, THE OVERALL PRECEDING WINTER AND SPRING WEATHER TRENDS (UPPER WIND FLOW AND SURFACE) WERE CONSIDERED WHEN EVALUATING THE FOLLOWING SUMMERS.

AFTER PEAKING LATE LAST YEAR, THE SOLAR FLARE ACTIVITY IS EXPECTED TO CONTINUE TO GRADUALLY DIMINISH THROUGH THE REMAINDER OF 2002. OTHER ITEMS OF IMPORTANCE: THE TREND OF THE EASTERN PACIFIC OSCILLATION (EPO) AND THE NORTH ATLANTIC OSCILLATION (NAO), THOUGH THEIR EFFECTS ON OUR WEATHER ARE SOMEWHAT LESS IN THE SUMMER AS OPPOSED TO THE WINTER. FINALLY, THE OVERALL SPRING WEATHER PATTERN MUST BE A CONSIDERATION IN THE OUTLOOK.

THE EASTERN PACIFIC OSCILLATION (current data) WAS PRIMARILY POSITIVE DURING MUCH OF THE WINTER AND THIS HELPED CONTRIBUTE TO OUR MILD WINTER. THIS IS BECAUSE THE POSITIVE EPO WAS REFLECTED BY TROUGHING ALONG THE WEST COAST WHICH BROUGHT THE MILD PACIFIC AIR WELL INTO THE COUNTRY. THIS SPRING, HOWEVER, THE EPO HAS BEEN DOMINATED BY A NEGATIVE PHASE WHICH GENERALLY AIDS IN BRINGING COOLER THAN NORMAL TEMPERATURES INTO THE REGION. IN ADDITION, THE NORTH ATLANTIC OSCILLATION (current data) HAS BEEN NEUTRAL TO NEGATIVE A GOOD PORTION OF THE SPRING WHICH HAS ALSO CONTRIBUTED TO OUR COOLER THAN NORMAL WEATHER (ONE MIGHT REMEMBER THAT DURING THE WINTER, THE NAO WAS DOMINATED BY A POSITIVE PHASE WHICH LED THE UNSEASONABLY MILD WINTER). IF THE ABOVE SCENARIOS WERE TO CONTINUE INTO THE SUMMER, THIS WOULD SUPPORT AN OVERALL, COOLER THAN NORMAL SUMMER.

ANOTHER CONSIDERATION THAT MUST BE MADE IS THE RELATIVELY WET SPRING MOST OF SOUTHEAST LOWER MICHIGAN HAS EXPERIENCED. THIS HAS MAINLY BEEN BROUGHT ABOUT BY THE PERSISTENT STORM TRACK FROM THE MIDWEST INTO THE NORTHERN OHIO VALLEY. THIS FAVORED TRACK SHOWED LITTLE SIGNS OF ABATING THROUGH MAY AS HEAVY AMOUNTS OF RAIN WERE DUMPED TO THE SOUTHWEST AND SOUTH OF MICHIGAN. THEREFORE, THE SOIL CONDITIONS (current data) REMAIN VERY WET OVER PORTIONS OF THE MIDWEST AND OHIO VALLEY. IF THIS PATTERN PERSISTS, IT WOULD BRING THE POSSIBILITY OF ABOVE NORMAL RAINFALL FOR AT LEAST PARTS OF THE LOWER GREAT LAKES REGION.

THE FOLLOWING TABLE REPRESENTS THE SUMMERS RESEARCHED (ALL DATA IS FROM DETROIT WHICH HAS THE LARGEST DATA BASE).

(TABLE-1)

SUMMER                                                         
YEAR           JUNE         JULY         AUGUST            SUMMER
------------------------------------------------------------------------
            TEMP/PRECIP  TEMP/PRECIP   TEMP/PRECIP        TEMP/PRECIP
1881        64.4/5.90    74.6/3.33     74.2/1.32      +/- 71.1/10.55 +
1896        67.9/6.97    71.4/5.39     70.3/4.60        - 69.9/16.96 +
1931        69.6/2.27    77.6/1.81     73.3/ .84        + 73.5/ 4.92 -
1953        70.9/3.09    73.5/2.65     74.3/1.52        + 72.9/ 7.26 -
1957        68.7/3.23    72.8/5.98     70.2/1.99        - 70.6/11.20 +
1982        64.2/4.11    72.4/4.78     67.7/ .72        - 68.1/ 9.61 +/-
1991        72.4/1.89    74.9/1.23     73.4/4.31        + 73.6/ 7.43 -
1997        69.5/3.17    72.2/2.62     68.1/3.22        - 69.9/ 9.01 -
--------------------------------------------------------------------
1971-2000
NORMAL      69.0/3.55    73.5/3.16     71.8/3.10          71.4/ 9.81
_____________________________________________________________________

+   ABOVE NORMAL
-   BELOW NORMAL
+/- NORMAL (WITHIN .5 DEGREE OR .50 PRECIPITATION)

SUMMER STUDY RESULTS

ONE OF THE FIRST THINGS THAT STRIKES THE OBSERVER WHEN LOOKING AT THE ABOVE SUMMER DATA IS HOW FAIRLY SYMMETRICALLY DIVIDED THE TEMPERATURE AVERAGES AND PRECIPITATION TOTALS ARE. OUT OF THE EIGHT SUMMERS, FOUR WERE COOLER THAN NORMAL, THREE WERE WARMER THAN NORMAL AND ONE PLACED NEAR NORMAL (OR WITHIN A HALF DEGREE OF NORMAL +/-). IN ADDITION, FOUR SUMMERS WERE DRIER THAN NORMAL, THREE WETTER THAN NORMAL, AND ONE, THE RAINFALL TOTALED NEAR NORMAL (WITHIN A HALF INCH OF NORMAL).

REVIEWING PAST WINTERS IN THE LIST, 1930-(1931), AND TO A LESSER EXTENT 1990-(1991) AND 1952-(1953) ALL RESEMBLED THIS PAST WINTER WITH MILD TEMPERATURES (AND THOUGH NONE WERE AS WARM, THE WINTER OF 1952-53 DID PLACE IN AT 8TH WARMEST AS OPPOSED TO LAST WINTERS 5TH PLACE). BASICALLY, THESE THREE WINTERS MEASURED AROUND NORMAL TO BELOW NORMAL SNOWFALL (THOUGH 1952-53 BY FAR HAD THE LEAST SNOWFALL WITH ABOUT HALF AS MUCH /16.6"/ THAN MEASURED THIS PAST WINTER /33.7"/). IT IS VERY INTERESTING TO NOTE, THE SUMMERS (1931/1953/1991) THAT FOLLOWED THESE ABOVE THREE WINTERS WERE BASICALLY WARM AND SOMEWHAT DRY.

HOWEVER, MOVING TO THE PAST SPRINGTIME WEATHER IN THE STUDY REVEALS MORE INTERESTING AND CHALLENGING VARIABLES. THIS PAST SPRING OF 2002 HAS BEEN GENERALLY COOL AND WET WITH AN AVERAGE TEMPERATURE OF 46.4 DEGREES IN DETROIT AND RAINFALL TOTALING 10.36 INCHES. SCANNING THE PREVIOUS SPRING PERIODS SHOWS THAT THE SPRING OF 1997 HAS ONE OF THE BEST CORRELATIONS IN REGARDS TO BOTH TEMPERATURE AND RAINFALL. THE AVERAGE SPRING TEMPERATURE IN 1997 WAS A COOL 45.0 DEGREES AND RAINFALL TOTALED 10.25 INCHES. THE SUMMER THAT FOLLOWED WAS GENERALLY COOLER AND JUST A BIT DRIER THAN NORMAL. AND, WHILE OTHER SPRING PERIODS IN THE STUDY MAY HAVE RESEMBLED THIS PAST SPRING AS FAR AS COOL TEMPERATURES, THEY TURNED OUT TO BE DRIER. CONVERSELY, WHILE SOME OF THE SPRINGS WERE WET LIKE THIS PAST ONE, THEY TURNED OUT TO BE WARMER. CHECKING BACK TO OUR AFOREMENTIONED SIMILAR MILD WINTER OF 1930-31, THE AVERAGE TEMPERATURE OF 47.0 DEGREES THAT FOLLOWED IN SPRING (1931), NEARLY MIRRORED OUR PAST SPRING TEMPERATURE OF 46.4. THE DIFFERENCE HERE, HOWEVER, WAS THAT THE SPRING OF '31 WAS CONSIDERABLY DRIER.

COLDEST MAY DATA

WITHOUT A DOUBT THE MOST INTERESTING (AND SOMEWHAT SURPRISING) DATA REVIEWED WAS THE COLDEST MAY DATA AND THE SUBSEQUENT SUMMERS. SINCE THIS PAST MAY WAS INDEED IN THE TOP 20 COLDEST, IT WAS THOUGHT TO BE AT LEAST SOMEWHAT RELEVANT TO COMPARE THE TOP 20 COLDEST MAYS IN DETROIT (EXCLUDING THIS YEAR) TO THEIR FOLLOWING SUMMERS. THIS WAS TO SEE IF THERE WAS ANY CORRELATION BETWEEN A COLD MAY AND COOL SUMMER. WELL, INDEED THERE WAS A CORRELATION, SINCE OUT OF THE 20 COLDEST MAYS, 16 SUBSEQUENT SUMMERS AVERAGED BELOW NORMAL (OR WERE RELATIVELY COOL), 3 WERE WITHIN A 1/2 DEGREE OF NORMAL /71.4/ AND ONLY ONE WAS ABOVE NORMAL (AND THAT WAS JUST BY .7 TENTHS /72.1/. NOW, WHILE 16 SUMMERS AVERAGED BELOW NORMAL, THAT DOES NOT MEAN ALL MONTHS IN THOSE SUMMERS AVERAGED BELOW NORMAL. THERE WERE SOME WARMER THAN NORMAL SUMMER MONTHS, BUT THEY WERE IN THE MINORITY. CHECKING THE INDIVIDUAL SUMMER MONTHS, ALL HAD AROUND A 70 PERCENT CHANCE OF BEING BELOW NORMAL BUT IT WAS AUGUST AND JUNE THAT CONTAINED THE LARGEST DEPARTURES BELOW NORMAL. AUGUST'S AVERAGE TEMPERATURE DEPARTURE WAS -3.3 /68.5/ AND JUNES WAS -3.1 /65.9/, WHILE JULY'S AVERAGE BELOW NORMAL DEPARTURE WAS -2.6 /70.9/. THIS DATA STRONGLY SUGGESTS THAT WHEN RESEARCHING THE TOP 20 COOL MAYS ONLY, THE COOL LATE SPRING PATTERN BASICALLY TENDED TO "HANG AROUND" INTO, AT LEAST, EARLY SUMMER.

IT IS IMPORTANT TO STATE HERE THAT THIS DOES NOT NECESSARILY MEAN THAT A BELOW NORMAL AVERAGE TEMPERATURE FOR MAY SUGGESTS A COOLER THAN NORMAL SUMMER, SINCE ONLY THE TOP 20 COLDEST MAYS WERE CHECKED.

THE PRECIPITATION DATA DURING THE SUMMERS FOLLOWING THE TOP 20 COOLEST MAYS WAS MORE MIXED. OUT OF THE 20 SUMMERS, TEN WERE DRIER THAN NORMAL, EIGHT WERE WETTER AND TWO WERE NEAR NORMAL (WHICH AGAIN, IS WHEN USING THE WITHIN .50 INCH OF NORMAL STANDARD STATED ABOVE).

SUMMARIZING

THE CLIMATIC PREDICTION CENTER HAS STATED THAT SOUTHEAST LOWER MICHIGAN HAS EQUAL CHANCES OF ABOVE OR BELOW NORMAL TEMPERATURES AND PRECIPITATION THIS SUMMER. AND, IF YOU KEEP ONE EYE ON THEIR PREDICTION AND ONE EYE ON THE SOMEWHAT CONFLICTING ABOVE DATA, THIS OUTLOOK IS QUITE REASONABLE. THIS IN-HOUSE DATA SUPPORTS NEARLY EQUAL CHANCES OF THIS SUMMER BEING WARMER THAN NORMAL OR COOLER THAN NORMAL, WITH A LEAN TOWARD COOLER THAN NORMAL (ESPECIALLY IF ONE CONSIDERS THE ABOVE COOLEST MAY FINDINGS AND RECENT EPO TRENDS). AND, EVEN THOUGH THERE WERE SOME NOTABLY DRY SUMMERS IN THE STUDY, THERE WERE ALSO SOME VERY WET ONES (AGAIN, THIS PATTERN WAS ALSO SEEN IN THE COOLEST MAY FINDINGS). ALSO, IN THE SAME TOKEN, ONE CAN HARDLY IGNORE THE WET PATTERN ON OUR SOUTH DOORSTEP THIS PAST SPRING. WHEN ALL THINGS ARE CONSIDERED, RAINFALL CHANCES ARE FAIRLY EVENLY DIVIDED BETWEEN ABOVE AND BELOW NORMAL, WITH A LEAN TOWARD ABOVE NORMAL.

FINALLY, TO REALLY SHOW HOW EVENLY DISTRIBUTED THE ORIGINAL EIGHT SUMMERS IN THE STUDY WERE: WHEN ONE AVERAGES ALL THE SUMMER TEMPERATURES, THE SUMMER TEMPERATURE COMES TO 71.2 (BASICALLY ON PAR WITH THE NORMAL OR AVERAGE). IF THE SAME IS DONE WITH THE PRECIPITATION (AND MAYBE NOT TOO SURPRISING) THE AVERAGE RAINFALL COMES TO 9.62 INCHES (WITHIN NORMAL RANGE AT JUST .19 INCH BELOW THE NORM OF 9.81).

IN ANY EVENT, IT WILL BE INTERESTING TO SEE IF THE RESULTS FROM THE TOP 20 COLDEST MAY RESEARCH HOLDS TRUE FOR THIS SUMMER.

CHECK BACK IN SEPTEMBER TO SEE THE "SUMMER OF 2002" SUMMARY!



** Note: images linked to from within this article are static and will not update, unless noted as "current data"


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