May 15-28, 2005 Pattern Discussion

[donsutherland1]

Last week’s discussion raised a number of issues of what one might expect for the May 8-21, 2005 period.

• Northeast/Mid-Atlantic: Following the weekend nor’easter, May 8 will likely see temperatures average below normal in New York City and Boston with Washington, DC averaging near or above normal. The May 9-12 period should see Washington, DC through Boston average warmer than normal. One or more days should reach 70° or above in New York City and perhaps Boston. Washington, DC should see one or more days reach 80° and it is even possible that Philadelphia sees one or more 80° readings. Showers could precede cooler air for the May 13-15 period.

May 8 anomalies:
Boston: -10°
New York City: -3°
Washington, DC: +2°

May 9-12 anomalies:
Boston: -1.5°
New York City: Normal
Washington, DC: +3.3°

70° or above days (May 9-12):
Boston: 1
New York City: 2

80° or above days (May 9-12):
Washington, DC: 1

May 12 Rainfall:
New York City: Trace

• The May 8-15 period will feature generally above normal readings for Chicago and Detroit. At least one day could see the mercury reach or exceed 80° in both cities, especially during the second half of this period. Afterward, it could turn briefly cooler before a new warming trend begins by the middle of the following week.

May 8-12 anomalies:
Chicago: +5.0°
Detroit: +3.0°

80° or above days (May 8-12):
Chicago: 2; highest: 85°, May 8
Detroit: 1; highest: 83°, May 10

It turned noticeably colder on May 12

• The Central Plains will likely see above normal readings for the May 8-13 period. Both Kansas City and Omaha should see at least one 80° reading and it is possible that Kansas City’s highest temperature could reach or exceed 85°.

May 8-12 anomalies:
Kansas City: +8.0°
Omaha: +6.0°

80° or above days (May 8-12):
Kansas City: 3; highest: 87°, May 10
Omaha: 2; highest: 90° May 10

• The May 8-11 period should feature near normal to somewhat cooler than normal readings along with frequent precipitation in Seattle. Total precipitation could reach 0.35” or more. May 13-15 should see warmer readings.

May 8-11 anomaly: +0.8°; May 8-10 rainfall: 0.72”. May 13 saw warmer than normal readings with temperatures well into the 60s at Seattle by mid-afternoon.

• Los Angeles should see near normal to somewhat above normal readings during the May 8-10 period. May 11-14 should be warmer than normal.

May 8-10 anomaly: -3.0°; May 11-13 anomaly: +2.7° with the temperature reaching 87° in Downtown Los Angeles on May 13.

The May 15-28, 2005 Ideas:

• Northeast/Mid-Atlantic: Courtesy of a strong block that will not come to an end until near the end of May, a trough with possible wet weather is likely in the eastern United States next week. May 15-16 should see showers with readings running near or perhaps somewhat above normal, especially in the Mid-Atlantic region. The May 17-21 period will likely experience below normal readings. Rain is possible in the May 18-20 timeframe and a few spots could receive more than 0.50”. After the next weekend, moderation is likely.

• The May 15-21 period will likely see readings run below normal in both Chicago and Detroit. Some showers and thundershowers are likely in the May 18-19 period. After the weekend, near normal readings are likely.

• The Central Plains will likely see a major outbreak of severe weather next week. Omaha will likely see temperatures run above normal during the May 16-21 period. Kansas City will be cooler as it is closer to the battle zone between air masses. However, the May 17-21 period there should be somewhat warmer than normal. May 17-19 could see an impressive outbreak of severe weather in parts of the Central Plains. Severe thunderstorms with hail and possible tornadoes could result.

• Seattle will likely see readings in the May 16-20 period average somewhat below normal along with rainfall in spite of the earlier longer-range idea of normal to somewhat above normal temperatures. The return of the warmth will occur just after that period. Warmer than normal readings are likely in the May 21-25 timeframe and possibly longer.

• Los Angeles will likely see near normal readings during the May 16-18 period. More unseasonable warmth is likely in the May 19-23 timeframe and at least one day could see the mercury exceed 80°.

Extremes in the North Atlantic Oscillation (1950-Present):

• January: Highest: +5.464 1/1/1983; Lowest: -5.692 1/22/1958
• February: Highest: +4.508 2/11/1989; Lowest: -6.962 2/13/1978
• March: Highest: +5.412 3/22/1986; Lowest: -6.967 3/3/1962*
• April: Highest: +4.816 4/14/1990; Lowest: -4.516 4/25/1995
• May: Highest: +3.940 5/9/1988; Lowest: -3.465 5/13/1993
• June: Highest: +2.887 6/1/1970 & 6/2/1986; Lowest: -3.146 6/12/1971
• July: Highest: +2.453 7/13/1994; Lowest: -3.001 7/13/1962
• August: Highest: +2.369 8/31/1999; Lowest: -3.191 8/14/1964
• September: Highest: +3.330 9/26/1989; Lowest: -2.984 9/11/1971
• October: Highest: +3.811 10/25/1969; Lowest: -3.963 10/17/2002
• November: Highest: +4.583 11/10/1993; Lowest: -4.783 11/26/1985
• December: Highest: +5.884 12/31/1983*; Lowest: -5.653 12/18/1963

* Denotes all-time record

• Days at -6.000 or below:15
March 10-11, 1951; March 9, 1958; February 27, 1962; March 1-4, 1962; February 22, 1965; February 10-14, 1978; February 25, 2005

• Days at 0.000: 5
June 14, 1959; January 20, 1961; May 2, 1964; May 25, 1996; October 31, 2003

• Days at +5.000 or above:7
December 31, 1982; January 1 and 2, 1983; December 30-31, 1983; January 1, 1984; March 22, 1986