A serious fall storm is approaching. Here is the synopsis from the offshore weather forecast from the National Weather Service:
.SYNOPSIS...A LOW PRESSURE TROUGH OF 29.4 INCHES OVER THE UPPER GREAT LAKES WILL DISSIPATE THIS AFTERNOON AS A LOW PRESSURE TROUGH OF 29.1 INCHES EMERGES OVER THE PLAINS STATES. LOW PRESSURE OF 28.9 INCHES WILL THEN ORGANIZE ALONG THE TROUGH OVER MINNESOTA TONIGHT. LOOK FOR THE LOW TO DEEPEN TO 28.4 INCHES AS IT MOVES TO NEAR INTERNATIONAL FALLS MINNESOTA BY TUESDAY EVENING. AS THE LOW MOVES ACROSS NORTHERN ONTARIO TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...IT WILL GRADUALLY WEAKEN TO 29.1 INCHES. THE LOW WILL THEN MOVE TO QUEBEC THURSDAY AS HIGH PRESSURE OF 30.4 INCHES SETTLES OVER THE PLAINS STATES. THE HIGH WILL THEN MOVE TO THE GREAT LAKES AND OHIO VALLEY FRIDAY.
Here is the offshore forecast:
LAKE SUPERIOR EAST OF A LINE FROM MANITOU ISLAND TO MARQUETTE MI AND WEST OF A LINE FROM GRAND MARAIS MI TO THE US/CANADIAN BORDER BEYOND 5NM FROM SHORE- 959 AM EDT MON OCT 25 2010 ...GALE WARNING IN EFFECT FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON... ...STORM WARNING IN EFFECT FROM TUESDAY AFTERNOON THROUGH LATE WEDNESDAY NIGHT... .REST OF TODAY...SOUTH WINDS 5 TO 15 KNOTS BACKING SOUTHEAST BY MID AFTERNOON. ISOLATED RAIN SHOWERS. WAVES 3 TO 5 FEET SUBSIDING TO CALM TO 2 FEET. .TONIGHT...SOUTHEAST WINDS 10 TO 20 KNOTS INCREASING TO 20 TO 30 KNOTS AFTER MIDNIGHT. A CHANCE OF RAIN SHOWERS. WAVES BUILDING TO 4 TO 7 FEET. .TUESDAY...SOUTHEAST GALES TO 40 KNOTS BECOMING SOUTH GALES TO 45 KNOTS BY MID AFTERNOON. RAIN SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS THROUGH EARLY AFTERNOON...THEN A CHANCE OF RAIN SHOWERS. WAVES BUILDING TO 12 TO 17 FEET. .TUESDAY NIGHT...SOUTHWEST STORM FORCE WINDS TO 50 KNOTS. A CHANCE OF RAIN SHOWERS. WAVES BUILDING TO 20 TO 25 FEET. .WEDNESDAY...SOUTHWEST STORM FORCE WINDS TO 55 KNOTS BECOMING WEST STORM FORCE WINDS TO 60 KNOTS BY MID AFTERNOON. RAIN SHOWERS LIKELY. WAVES BUILDING TO 25 TO 30 FEET. .WEDNESDAY NIGHT...WEST STORM FORCE WINDS TO 55 KNOTS DIMINISHING TO GALES TO 40 KNOTS AFTER MIDNIGHT. A CHANCE OF RAIN SHOWERS. WAVES SUBSIDING TO 15 TO 20 FEET. .THURSDAY...NORTHWEST GALES TO 35 KNOTS DIMINISHING TO 20 TO 30 KNOTS. A CHANCE OF RAIN SHOWERS. WAVES SUBSIDING TO 5 TO 8 FEET.
Note the 60 knots of wind and 25-30 foot seas on wednesday. That is around 70mph of wind!
Here is a chart of the storm for tuesday morning from the National Weather Service:
Click on the image to see it enlarged. Note the size of the storm. It covers a huge amount of area, larger than the middle of the US from the gulf of Mexico to the Canadian border.
Now see what it is forecasted to do wednesday morning:
You can see it intensify on wednesday. Note the number of lines and how closely spaced they are, this indicates the intensity/speed of the wind. Very similar to a topo map where the lines indicate the contour/steepness of the land.
On the Beaufort Scale this ranks as a force 11, a violent storm. The next and final step is hurricane force which is over 64 knots or 73 mph of wind. Some wind scales list the effect on land of this wind as: Large limbs knocked down; powerlines knocked down; a few house shingles torn off.
This storm is stronger off shore than along the shore, thanks to the wind blowing off the land onto the lake. Otherwise, the Marquette shoreline would be an interesting place the next couple of days.