June is historically the least active month of the hurricane season, but that doesn’t mean the first month of the season can’t bring its fair share of issues. Most commonly, it’s the weak and sloppy systems – waterlogged disturbances that may not even muster up a name – that wreak the most havoc in June. Short-timer Arthur last week punctuated this truth, and even though it did briefly get a name, the widespread and locally catastrophic flooding that followed came after it had already unraveled into a remnant low.

Analysis of rainfall observed over the past week (based on all available station observations) versus what is typical for the time of year. The analysis shows pockets where rainfall over the past week was 4-8x what is would usually be. Many locations across the Central Gulf Coast (southeastern Louisiana, southern Mississippi) saw one of their wettest June weeks on record last week. The rainfall last week catapulted the New Orleans metro – whose official airport records extend back 80 years – to its third wettest June on record so far (behind only 2001 and 1987). Credit: High Plains Regional Climate Center.

Mercifully for areas in Texas, Louisiana, and coastal Mississippi saturated with tropical rains last week, Mother Nature will turn off the tropical spigot this week, as high pressure takes over and ushers in the hottest temperatures of the year so far. Already heat advisories are in effect today across parts of southern Louisiana in anticipation of feels-like temperatures approaching 110 degrees, with additional heat advisories expected this week across the Deep South.

The one-two punch that’ll shut down the Atlantic to close out June

We started reading the stormy tea leaves of mid-June – brought on by the active phase of the Madden-Julian Oscillation or MJO – way back on the second day of the hurricane season. While El Niño was heating up in the eastern Pacific, the Gulf and western Caribbean showed signs of punching through – at least briefly – as the upper-level wind configuration opened a narrow lane for tropical mischief.

Now that we’re on the other side of Arthur and its remnants, the tropical Atlantic is about to get pummeled by the one-two punch of El Niño and continent-sized plumes of Saharan dust, coming as dust season peaks for the end of June and beginning of July.

The warming of the ocean waters in the eastern equatorial Pacific that define El Niño takes time to link up with the atmosphere and begin affecting the circulation patterns that ultimately dampen Atlantic tropical activity. We’re seeing that atmospheric coupling beginning now, with rising air dominating the Pacific and sinking air over the North Indian Ocean torpedoing development odds through the tropical Atlantic.

Areas of rising (blue/cool colors) and sinking (red/warm colors) air straddling the equator (between 15°N and 15°S) by global longitude (x-axis) from late May (top of the chart) through August 6th (bottom of the chart). The time vs. longitude chart is known as a Hovmöller diagram and shows the global progression of the Madden-Julian Oscillation or MJO and its Kelvin Wave components. The solid greens and blues (something called a “standing wave”) between 180 and 90 degrees west longitude indicate El Niño is coupling with the atmosphere leading to a change in circulation patterns that will deter tropical activity across the Atlantic for much of the hurricane season ahead. Credit: ECMWF.

A ribbon of exceptionally strong wind shear stretching clear through the tropical belt of the Atlantic basin will mean tropical tumbleweeds for the foreseeable future.

Forecast wind shear departure from average (warmer colors indicate areas of higher-than-average wind shear) for the last week of June into early July from the European model ensemble system. Long-range forecast models show a belt of extremely hostile wind shear through the tropical Atlantic, consistent with a strong El Niño. Credit: TropicalTidbits.com.

Even into July, any tropical threats will probably originate closer to the U.S. and around the southeastern U.S. coastline where the effects of El Niño are less noticeable. But for now, the triggers we’d look to closer to home – like unusually strong cold fronts or large thunderstorm complexes moving off the mainland – aren’t in the cards, and June should close with little fanfare across the Atlantic.

June out like a lamb in the Atlantic

El Niño hitting its stride with Saharan dust season peaking means tumbleweeds in the Atlantic to close out the month

The one-two punch that’ll shut down the Atlantic to close out June

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Michael Lowry