Monday, November 9, 2009

Ida strikes, November soaking shaping up?

No, the two headlines are not related. We will not see any rain from Tropical Storm Ida, although the idea is not as bizarre as it might appear at first blush. About once a decade a gently used hurricane strikes the Gulf coast, and then races northward across the Plains, weakening rapidly as it passes over land, starved of the warm ocean water that sustained it earlier. By the time these washed-up tropical swirls reach Minnesota winds are under 20-30 mph, but rainfall can be heavy, even at this northerly latitude. It's rare, but not impossible, and no, it's physically impossible for a hurricane to reach this far inland (intact). The Great Lakes are too small (the water far too chilly) for hurricane development. Hurricanes require little or no wind aloft to form - that's why we had so few tropical systems this year. El Nino (it's baaack) kept an unusually strong, persistent subtropical jet stream howling over Texas, Florida and the Caribbean, literally shredding tropical disturbances before they had a chance to get going. That's the paradox of hurricanes: they can spawn sustained winds of 150-200 mph at ground level, but to grow (and survive) the winds aloft, some 4-8 miles aloft, have to be nearly nonexistent.

Tropical Storm Ida. Weakening rapidly over cooler water in the northern Gulf of Mexico, the soggy remains of Hurricane Ida are coming ashore near Mobile, Alabama this morning. Sustained winds are tropical storm force, about 50-60 mph, still capable of a "storm surge" of 3-7 feet above normal. Expect significant beach erosion and coastal flooding from Mobile eastward into the panhandle of Florida with some 5-10" rainfall amounts well inland.

Yesterday was stunning, no disagreement there. The official high (in the shade, where the temperature should be measured) was a respectable 61 degrees F, well above the normal high of 44 for November 9. For the record the first week of November has been averaging over 7 degrees above normal. Balmy September, miserable, soggy, snowy October, and now (finally!) Indian Summer makes a welcome appearance in November. What took you so long? So much for "normal weather" right?

The magic hangs on today, nearly as phenomenal as yesterday was, with brilliant sun set against a topaz-blue sky, very light breezes, no bugs (thanks to last month's freeze), no ragweed, no pollen, no humidity. No-vember. Yes, I could get accustomed to 60 degrees - what - a little more than 5 weeks away from the Winter Solstice. And no, you can't necessarily chalk this hypnotizing spell of weather up to global warming. No single event, whether it's a warm front, Indian Summer, rain storm or blizzard can be directly tied to climate change. It IS true that, in general, fall has been consistently hanging on an extra week or two, spring comes 1-2 weeks earlier than it did in the 1960s. I'm not making that up - that's according to our friends at NASA. Maybe I'm imagining it (too much heavy partying in KARE-11's "backyard" in the 80s?) but extreme weather has been getting more extreme, not just here in North America, but worldwide. Weather has always been extreme, but lately, the past few decades, the AMPLITUDE of these extremes have been, well, even more extreme. Hotter high temperatures, colder low temperatures, more frequent rainfall records. Over time you would think (intuitively) that it would become harder and harder to set a weather record. And yet the data shows just the opposite: the tempo of weather records has reached a crescendo in recent decades, more severe local storms, more costly natural disasters. Natural or man-made? Hard to say with total certainty - I just know (in my gut and my head) that something has changed since about 1980, give or take. The notion of "normal weather" is an even bigger joke than it's ever been. We just zig and zag from one record to the next, scratch our heads, and wonder what the heck is going on.

Potential for another soaker? Long-range (GFS) models are printing out over 2" of rain by Tuesday of next week, the heaviest rain predicted for Sunday PM into Monday. Stay tuned.

Soak up today's lukewarm, 60-degree sunlight, because the weather will slowly sour Wednesday, a period of light rain likely by Thursday, possibly lingering into part of Friday. A much more significant storm is shaping up for late in the weekend and Monday of next week as a deep area of low pressure tracks across the Mississippi River Valley, temporarily stalling to our south over Iowa early next week, pulling Gulf moisture northward in the form of heavy, windswept rains. Yes, the atmosphere aloft will PROBABLY be warm enough for mostly rain late Sunday into Monday. The GFS model is hinting at some 1-2" rainfall amounts early next week. We'll see. I still don't see any bitter blasts or accumulating snow anytime soon, temperatures running 5-10 degrees above average into much of next week. Every passing day is a gift, making winter seem a bit shorter. For those of you dreading winter. If you have a hankering, an itch for snow, stay tuned. Your day is coming - watch out around Thanksgiving. That's when we often see our first significant accumulating snow event, coming when it can wreak the most havoc around Thanksiving travel time. What can possibly go wrong this year?

Monday Gulley-Washer? The GFS computer forecast for 6 am Monday shows an intense area of low pressure over Iowa, heavy rain wrapped around the storm, the heaviest bands of precipitation (yellows and reds) over southern and central Minnesota. It's early, but right now it appears that there may be enough warm air aloft for mostly rain across Minnesota, and amounts may be very significant.

Paul's Outlook for the Twin Cities

Today: Plenty of sun, light winds - stunning for mid November! Winds: SE 5-15. High: 61

Tonight: Partly cloudy, dry sky. Low: 38

Wednesday: Less sun, clouds increase during the day. High: 57

Thursday: Period of light rain likely. High: 51

Friday: More rain possible, still soggy, cool and damp. High: 49

Saturday: Brighter, drier with intervals of sun. High: 51

Sunday: Clouds increase, a cold rain arrives late in the day. High: near 50

Monday: Windy and raw with rain, possibly heavy at times. High: 47

Tuesday: Gusty and drier with more clouds than sun. High: 48

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