Pop up T-Showers; Florida Hurricane threat; Double-Dip La Nina?

Fickle Thursday:

Look for a few isolated "pop-up" showers & T-showers today around Minnesota & the Upper Midwest.

-Latest Twin Cities radar loop

What meteorologists refer to as a "weak synoptic pattern" is providing enough instability to generate the isolated T-Showers. Weak synoptic patterns are defined by the lack of a major focal point to generate storms...like a strong cold front or big low pressure system does.

The result is a higher degree of difficulty forecasting exact timing and location of storms.

There's just enough instability today that SPC has much of Minnesota under a slight risk for severe weather.

I don't expect a big widespread severe weather outbreak today, but one or two storms could approach severe limits.

Florida: Keeping a wary eye on the tropical Atlantic

Again, it's too early to issue any reliable hurricane forecasts a week in advance. But it's not too early to start paying attention when the same model insists on placing a (potentially strong?) hurricane somewhere near Florida late next week.

For the 3rd day in a row, the NCEP GFS model is developing a hurricane and tracking it westward to a position near south Florida sometime late next week.

There's a lot of open water and atmosphere between the tropical wave, which is still in the eastern Atlantic... and Florida.

Here's the latest from NHC.

A LARGE TROPICAL WAVE LOCATED ABOUT 875 MILES WEST OF THE CAPE VERDE ISLANDS CONTINUES TO PRODUCE LIMITED SHOWER ACTIVITY. SIGNIFICANT DEVELOPMENT IS NOT LIKELY DURING THE NEXT COUPLE OF DAYS. HOWEVER...ENVIRONMENTAL CONDITIONS COULD BECOME MORE CONDUCIVE FOR DEVELOPMENT AFTER THAT TIME. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT 15 TO 20 MPH.

Anything could happen in the next week, but if I lived in Florida I would have my "pre hurricane" action plan in full gear and be readying thing just in case this pans out next week. That's a good idea anyway during late August in the southeast USA.

Stay tuned.

"Double-Dip" La Nina?

It doesn't happen often, but there are signs that we may see a rare "double-dip" La Nina again next winter.

La Nina years (cold water in tropical Pacific) are usually separated by an El Nino episode (warm water) in between.

But every so often (2008-2009 & the mid 1970s) a La Nina will fade to neutral, only to regenerate again the next year.

Historical El Nino Southern Oscillation. La Nina episodes in blue, El Nino in red.

There are signs La Nina could regenerate next winter, and CPC has issued another "La Nina Watch."

The various climate models are split on what will happen next winter. Some say a weak El Nino, some are "ENSO neutral" and some say La Nina will return.

At this point I'd say it's a coin flip, but we may know more when the next ENSO advisories are issued in September and October.

Last winter's relatively strong La Nina may be the reason we saw heavy to record snowfall, and a cold spring. But all La Nina episodes are not equal in terms of the weather patterns they produce. I'd say it's unlikely we'll see another 86" of snowfall next winter in the metro, but I suppose anything is possible.

Again...stay tuned!

PH