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Dorian Weakening & September in July for Upper Midwest & Great Lakes

26 Jul 2013, 5:41 am
Canadian Leakage
Stare at the weather maps long enough and you begin to hallucinate. I’ve been telling you (ad nauseum) for years that something has changed on the maps – the pattern isn’t even close to what I grew up with in the 70s and early 80s. Weather getting “stuck” for extended periods of time. Odd gyrations in the jet stream steering winds.
John Mason at Skeptical Science writes: “Evidence is mounting to indicate that the response of the jet stream to polar amplification has been to tend to slow down and meander more, with a greater tendency to develop blocking patterns, which in turn prolong and intensify all sorts of extreme weather events.”
Northern latitudes are warming faster than mid latitudes, resulting in a 12 percent drop in average jet stream winds, which may slowing storms and hot high pressure ridges.
All or nothing? Drought or flood?

A Buckling Jet Stream. The map above shows predicted 500 mb winds (18,000 feet) at 12z Sunday morning, showing a massive cut-off low centered north of Green Bay, a swirl of unusually cold air aloft hovering over the Upper Midwest and Great Lakes. Typical for early October, not late July. The maps just keep getting stranger. Map credit: Weather Bell. 

30s in Northern Minnesota Saturday Night? Good grief – what next? One more symptom of an amped up jet stream taking some very unusual turns, more evidence of “Arctic amplification”. The map above shows predicted lows for Saturday night, upper 40s in the Twin Cities, low 40s from Brainerd to Bemidji. I’d bet a bagel Tower and Embarrass will record lows in the 30s early Sunday morning. Map courtesy of NOAA.

Summer Relapse. Residents from Minnesota to Michigan will be reaching for sweatshirts the next couple of mornings, lows dipping into the 40s and 50s with a stiff wind and a few instability showers. Meanwhile a tight little storm chugs up the East Coast, brushing Cape Cod and Boston with heavy rain. Showers and T-storms track across the Mid South, a few monsoon storms over the Southwest, while the West Coast remains bone dry. 84 hour NAM: NOAA.

Thawing Out….In Fairbanks. Another mixed-up, upside-down weather map. Fairbanks will be 20-25 degrees warmer than much of Wisconsin and northern Michigan by Saturday, a southward dip in a buckling jet stream plunging an airmass that would be right at home in late September into the Upper Midwest and Great Lakes. Free A/C? Plenty of free A/C. Details of today’s Climate Matters: “Travel to Alaska to warm-up? Yes,a big change in the jet stream is bringing much cooler temperatures to the lower 48. Chief Meteorologist Paul Douglas likes to call it Canadian Leakage. Then there’s Tropical Storm Dorian. The models are all over the place for where Dorian could wind up.”

Tropical Storm Dorian Update:

The big headline this morning is that Dorian has weakened and is becoming more disorganized.

Here is the latest from the National Hurricane Center. 

TROPICAL STORM DORIAN IS CENTERED NEAR 16.6N 39.6W AT 26/0300
UTC OR ABOUT 1350 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING W-
NW AT 17 KT. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO
55 KT. MINIMUM CENTRAL PRESSURE IS 1001 MB. PLEASE SEE THE
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
AND THE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34
KNHC FOR MORE DETAILS. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 16N-18N BETWEEN 37W-40W.
 THE
DYNAMICAL MODELS FORECAST THE RIDGE TO BUILD WESTWARD NORTH OF
DORIAN...WHICH SHOULD KEEP THE CYCLONE ON A GENERAL WESTWARD PATH
DURING THE FORECAST PERIOD.  THE GFS...NAVGEM...AND HWRF ARE THE
SOUTHERNMOST OF THE MODELS...FORECASTING THE STORM TO PASS NEAR OR
OVER HISPANIOLA IN 4-5 DAYS.  THE ECMWF...UKMET...AND CANADIAN
MODELS ARE THE NORTHERNMOST...FORECASTING A POSITION NEAR THE
BAHAMAS IN 5 DAYS. THE NEW TRACK FORECAST LIES BETWEEN THESE
SCENARIOS NEAR THE CENTER OF THE GUIDANCE ENVELOPE.


Late July Hurricane Climatology. I thought this was an interesting nugget, courtesy of Brian McNoldy, at The Capital Weather Gang: “…In the past 162 years, just three other storms were named (tropical storm intensity or greater) this far east during the entire month of July:  Anna 1969, Alex 1998, and Bertha 2008.  Dorian has joined that list, and for reference, its current location is marked with a red “D”… basically right on top of Bertha’s track; however, Dorian is not expected to curve out to sea so quickly…”

Image credit above: “The only three storms that were at least tropical storms at or near Dorian’s longitude during July going back to 1851.” (NOAA).

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Welcome to the WeatherNation blog. Every day I sift through hundreds of stories, maps, graphics and meteorological web sites, trying to capture some of the most interesting weather nuggets, the stories behind the forecast. I’ll link to stories and share some of the web sites I use. I’m still passionate about the weather, have been ever since Tropical Storm Agnes flooded my home in Lancaster, PA in 1972. I’ve started 5 weather-related companies. “EarthWatch” created the world’s first 3-D weather graphics for TV stations – Steven Spielberg used our software in “Jurassic Park” and “Twister”. My last company, “Digital Cyclone”, personalized weather for cell phones. “My-Cast” was launched in 2001 and is still going strong on iPhone, Android and Blackberry. I sold DCI to Garmin in 2007 so I could focus on my latest venture: WeatherNation. I also write a daily weather column for The Star Tribune startribune.com/weather And if you’re on Twitter, you’ll find me @pdouglasweather

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