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Category Archives: Seasons
We will not see 80 degrees again this year.
The last time Madison was officially 80 degrees or warmer was Sept. 21, the last official day of summer. In fact, 13 of the first 21 days of last month we were at least that warm — fairly remarkable. Continue reading
The Atlantic hurricane season is now more than two months old and has so far been fairly quiet with only three storms — all of them in the weakest category of tropical depression. This may well have been the case in the summer and fall of 1492 as well.
It is interesting to note that among the seemingly endless list of superstitions and fantastical falsehoods that surrounded voyages of exploration in the age of discovery — ranging from sea serpents of all kinds to boiling waters near the equator — there was no mention of hurricanes. This is obviously because no European had yet witnessed (and could not imagine) the frothing seas, with towering 100 foot waves, that these ferocious storms can create. Continue reading
Yes. Soil-derived aerosols, or dust, are abundant in our atmosphere. One source of dust is sandstorms over the Sahara. These storms whip small pieces of mineral dust from the desert into the atmosphere. Easterly winds then carry large plumes of Saharan dust away from the desert and over the Atlantic Ocean.
This weather system is referred to as a Saharan air layer, or SAL, and at times dust in the SAL has traveled to the Caribbean, Texas and Florida. Desert dust from the Sahara and Gobi deserts has been observed on the ice sheet of Greenland. Ice cores in Greenland provide a history of the dust deposition as it appears as layers in the ice. Continue reading
All things considered, we have really had a rather benign summer in southern Wisconsin thus far this year. Through Friday of last week, July was averaging just over 1 degree warmer than normal, with the majority of the contribution to this slightly warm month coming in the overnight lows, which have been 1.5 degrees above normal thus far. In addition, except for the 1.23 inches of rain we received when the heat broke July 23-24, we would be just about normal for July.
Somehow we got thinking about some characteristics of warm-season (May through October) precipitation in Madison in the midst of this spell of fine summer weather. Dr. Ed Hopkins at the State Climatologist’s Office was on the ready for our question, which was: What are the wettest and driest calendar days during the warm season in Madison? By “wettest” we mean the calendar day on which the most total accumulated precipitation has been recorded in Madison’s 153-year climatological record — and the least for the “driest” day. Continue reading
We have commented a number of times in the past few years about the areal extent of the hemispheric cold pool of air at 850 mb — about 1 mile above the surface — during the winter. As one might expect, that pool expands dramatically from October through February and then begins to contract as we move toward spring and summer.
Our analysis uses the minus 5 degrees Celsius (23 degrees Fahrenheit) isotherm (line of constant temperature) and has shown that the average winter cold pool area has systematically shrunk in the past 75 years. Continue reading