Best week of summer? El Nino pushing records

Somebody pinch me.

Bright sunshine. Dew points in the 50s. Pleasantly cool mornings and warm afternoons. No mutant bow shaped blobs on Doppler tearing up perfectly good trees.

Does it get any better than this?

Welcome to what could be the best week of summer across Minnesota so far.

Life on the backside of summer high pressure

We enjoy another day with balmy breezes and a comfortable air mass. Tomorrow winds turn south once again. The ongoing summer push-pull between free Canadian air conditioning and steamy summer air masses reverses trend Wednesday as another warm front rides north on the backside of high pressure.

National Oceanic and Atmospheric Administration

A few stray thundershowers ride the front in central Minnesota Wednesday into Thursday, but I think most of southern Minnesota will stay dry until Friday night.

Dew points begin to rise again tomorrow into the slightly sticky lower 60s. You’ll notice the humidity ramp up Thursday and Friday as dew points push the magical 70 degree mark once again.

European Centre for Medium-Range Weather Forecasts output, via Weatherspark

Second tornado confirmed Friday night

Friday night’s storms still reverberate as the last few homes get power back in the west metro. It’s good news when you’re part of a big power outage that can be quickly fixed by Xcel. Not so much if you’re the only home out on your street after massive storms.

Several of our friends in Deephaven in the west metro endured three full days without power. Time to pitch the spoiled freezer stock and make another trip to Costco.

It looks like Friday night’s storms won’t qualify as a derecho. The storms met the path length criteria for derecho of at least 240 miles, but severe gusts of at least 50 knots were not observed along the entire path. Here’s a look at the gusts along the storm front as the bow echo raced east from South Dakota through Minnesota and Wisconsin.

Interestingly the storm’s peak gusts  dipped some west of the metro before ramping up and pounding the metro with 60 to 70 mph winds. Notice how the echo shows a more pronounced bow shape as it surges through the metro early Saturday morning in this loop from Greg Carbon at the National Oceanic and Atmospheric Administration’s Storm Prediction Center.

NOAA

This system appears to fall shy of the consistent 50 knot wind gust criteria in NOAA’s definition of a derecho.

Definition of a derecho
A derecho (pronounced similar to “deh-REY-cho” in English, or pronounced phonetically as ““) is a widespread, long-lived wind storm. Derechos are associated with bands of rapidly moving showers or thunderstorms variously known as bow echoes, squall lines, or quasi-linear convective systems.

Although a derecho can produce destruction similar to that of a tornado, the damage typically occurs in one direction along a relatively straight path. As a result, the term “straight-line wind damage” sometimes is used to describe derecho damage. By definition, if the swath of wind damage extends for more than 240 miles (about 400 kilometers), includes wind gusts of at least 58 mph (93 km/h) along most of its length, and several, well-separated 75 mph (121 km/h) or greater gusts, then the event may be classified as a derecho.

NOAA

A second gustnado was confirmed by the Twin Cities National Weather Service near Eau Galle south of Menomonie as the storms raced into western Wisconsin.

1 N EAU Galle [Dunn Co, WI] NWS STORM SURVEY reports TORNADO of EF1 at 18 Jul, 1:52 AM CDT — OFFICIAL STORM SURVEY SHOWED AN 8 MILE LONG DAMAGE PATH FROM 147 AM TO 159 AM. 88 MPH WIND MEASURED 1 MILE NORTH OF EAU GALLE AT 152 AM. MAINLY TREE DAMAGE WAS OBSERVED.

The midnight tornado near Watertown, Minn., was the 17th so far this year in Minnesota. Last year, 28 tornadoes skipped across Minnesota. The 30 year average (1991-2010) is 45 per year.

El Nino setting records

It’s still early, but the exploding El Nino is the tropical Pacific is setting some records that rival the mega 1997-98 El Nino event. Today’s latest update from the Australian Bureau of Meteorology will turn heads for El Nino watchers.

El Niño continues to strengthen

Issued on 21 July 2015 |

The 2015 El Niño continues to develop. Weakened (or reversed) trade winds have resulted in further warming over much of the tropical Pacific Ocean. All key ENSO ocean monitoring areas have been more than 1 °C above average for 10 successive weeks—two weeks longer than the record in 1997. The eastern tropical Pacific is now at or exceeding +2 °C. In the atmosphere, the past week has seen the Southern Oscillation Index (SOI) drop to around −20, the lowest values of the event so far.

All international climate models surveyed by the Bureau of Meteorology indicate El Niño is likely to strengthen, and is expected to persist into early 2016. El Niño events typically peak during the late austral spring or early summer, and then weaken in the new year.

The impressive ribbon of red continues to expand in the tropical Pacific.

NOAA

Stay tuned.