Tropical Storm Dorian Forms

It has been rather quiet of late across the tropics as you would expect during the early part of the season, however we do now have a named storm on the charts and that name is Dorian. Dorian is a 50 mph storm heading west, northwest at 20 mph beneath the Mid-Atlantic ridge. Pressure is 1002mb.

This very small, quite well organised and compact looks set to better organise over the next 5 days or so despite a lot of dry around. How so? The small size and increasingly well organised core is all but protecting it from it’s inhibiting surroundings and so this system should be able to continue moving west towards the Leeward Islands without too much trouble.

The size is important here because a larger system would entrain the surrounding dry air and likely would cause it all sorts of problems. As for it’s small size, this system is more likely to continue that WNW track compared to feeling the weakness in the Mid-Atlantic ridge which there is well to the NW of Dorian.

Below is the current water vapour image.


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Notice the swirl of cloud well out ahead of Dorian. That’s an upper low which resides within a weakness in the ridge. Forecast models suggest that void closes and the upper low which may have induced shear within 5 days, dissipates, keeping Dorian on a mainly WNW track.

While this needs to be watched but there’s no imminent danger to the US, this system I believe has a lot going for it and the pattern is such that the Eastern US should pay close attention with the troughy pattern over the East, the lack of shear towards early next week as Dorian heads towards the Bahamas where water temperatures are plenty warm.

Speaking of water temperatures. Here they are.

Source: NHC

Source: NHC


Source: NHC

Source: NHC

Notice the yellow colours that this system is in at the moment. The NHC has in fact got the storm weakening temporarily and that’s due to those cooler waters but within just days it enters 80 degree waters and will likely encounter warmer and warmer water as it tracks west.

Below is the NHC forecast track.

Source: NHC

Source: NHC

Like I’ve already mentioned. The fact this system is becoming well organised and it’s very small, there is no reason to think that this cannot get all the way west 65-70 west before it makes a turn. By that point which would be early next week, the Eastern US may be a little more concerned. Also by that stage, a second trough would be dipping down the US East Coast but it’s the timing would is everything. The timing of the trough and the speed at which Dorian is moving, not forgetting the size of the system at this stage too.

It’s simply too far out to tell for sure but in all honesty. I think this thing has a chance at causing some problems for the US.

Here’s the GFS out at 240 hrs

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Notice this model has Dorian at roughly 73 west. If we have a storm here at this point, the timing of the Eastern trough will be everything. Keep in mind waters are well above normal along the East Coast.

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