Tropical Storm Isaias, earliest 9th storm on record by more than a week

Much greater than normal uncertainty on this system beyond a couple days at a time.

This season reaches the “I” storm at a record pace, beating out Irene on August 7th in 2005.

Even the National Hurricane Center points out in their guidance discussion that there are more than the usual number of question marks on this Tropical Storm.

The models are all over the road on its future path and strength so all bets are off right now.

The storm could intensify only to be sheared apart by the mountainous islands in its path and/or wind shear. If it skirts the islands and is not shredded apart by them and the out front shear relaxes then and only then would the threat of significant impact increase for the SE part of the country.

The various numerical equations both global and mesoscale show a wide variety of options with equal 1/3 weight for now.

So as far as impact on the states is concerned it therefore makes no sense to focus on the long range just yet. Impacts possible this weekend into early next week but details sketchy at best.

We can however apply the reasoning of synoptic meteorology to bracket the range of options as seen in the 500mb GFS ensemble mean jet stream pattern projection. The entity #9 will not be allowed by the laws of physics to go West of the Troff axis (588) or East of the Ridge Axis (591dm):

The chart below shows that the weaker a tropical system is the greater the future forecast track error:


Meanwhile, it looks like we will not see a return of the really big heat we just finished having for at least the next two weeks! Instead below-normal temperatures or at worst normal temperatures for this time of year for the next 5-15 days with above-normal rainfall as shown by the ECMWF Ensemble:

For more follow me on Twitter @MellishMeterWSB.

Kirk Mellish

Meteorologist

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