Tropical Storm Fred will have it better than Danny, Erika – but, not much

Tropical Storm Fred may be one of those storms that lags around.  Several computer forecast models try to turn the storm west and even the official NHC forecast takes the storm on a westward jog by the end of five days.  But, don’t be surprised if Fred isn’t even around in five days.

Satellite Presentation

The current overall appearance of Fred is pretty impressive – visibly.  High cirrus clouds are fanning out from the CDO in all quadrants.  Fred does have nice spiral banding on the east and the west side.  The overall CDO, however, has broken as the morning has progressed.

Earlier, Fred looked very impressive with an overall comma-shaped appearance.  In addition, cold cloud tops were building over the center of the storm.  That has since changed and, though Fred still has it’s comma-shape, IR imagery shows the colder cloud tops waning in both the CDO and the largest spiral band to the southwest.  The center of the tropical storm is located on the northwestern side of the coldest convection which is in the –70°C.

While Fred may become a hurricane as anticipated by the NHC the storm will need to improve its CDO from its current state.  Estimated wind radii from the NHC show a very symmetrical storm.  But, this doesn’t translate to the imagery at this point of time.  Fred will have to find a balance and pinpoint its surface center more or less right under the coldest cloud tops which must be steady.

Atmospheric Moisture

The image below shows some considerable dry air located to the north and west of TS Fred.  This dry air is likely getting entrained into Fred which is causing the ragged appearance in the IR image above.  While TS Fred does have plenty of moisture available to work with – notice it is tapped into two sources; from the south/southwest and from the west – it is likely Fred will struggle maintaining decent consistency with it’s convection that I’m looking at.

It’s only going to get worse for Fred if the storm takes the forecasted track – which it most certainly will.  Fred will move into an even drier region and is likely to lose it’s connection with the south/southwest moisture stream.  In addition, Fred has some Saharan dust to contend with.  As Fred begins to turn north it will be right in the mix of this air and will draw it into the system enhancing disorganization and weakening.  Don’t be surprised if it even happens well before the storm turns north – like, today.

Forecast Models

There isn’t much change in the overall idea of the computer forecast models – which is somewhat interesting.  Several of the models continue to push Fred on a northward turn soon inline with previous runs and the official NHC forecast.

What’s interesting is the GFS ensemble which, again, insists on turning the storm back to the west-southwest.  This is despite the GFS and GFDL following – more or less – the forecast tracks above.

Notice in the proceeding image how the GFS has a high pressure ridge in front of the storm’s forecasted northward track:

Here’s the scenario currently:  it is believed an approaching trough will weaken an already-weak high pressure ridge to the north of Fred.  This is what is expected to turn Fred north.  However, it appears possible at this time that trough is not guaranteed to pick up Fred.  This will largely depend on how far north Fred gets as the trough gets closer.  However, most of the computer models seem to agree Fred will progress to roughly 20°N in 4-5 days.  The trough is most likely to miss catching Fred, therefore leaving the system hanging in the Atlantic.

This is where it gets interesting.  As the trough passes the high will rebuild back into place.  The two questions are:

• how strong
• how long

Season tendencies this year have been moderate high pressure ridges building in across the Atlantic but not holding anchor as in years past.  A rebuilding high would steer Fred back more towards the west or, as the GFS Ensemble wants to do, but way too early, west-southwest.  Thereafter, Fred would continue about a more westward track until another approaching trough breaks the ridge and then picks up Fred – likely well before Fred even poses a threat to Bermuda or the United States.

Keep in mind, I’m stating this based on past-experience.  I’ve seen some of the models runs and I get what they are trying to do.  I’ve seen it happen before and it seems very likely to happen again in this instance.  I think the NHC is wondering the same – hence the westward jog at the end.

The question will be: what kind of system is TS Fred by then?  Shear is expected to increase over the storm as it begins to turn north.  In addition, Fred will be getting into bare-minimum SSTs supportive of tropical cyclones.  It is quite possible Fred could be reduced to a low/mid-level circulation at that point which would alter its forecast tremendously.  But, now we’re getting into what-if scenarios that could just continue a thousand ways.  Bottom line, I think Fred will not just take off into the north Atlantic like Bill did.  But, it won’t be an impressive storm late this week.

You can see in the image above Fred is forecast to become a hurricane, albeit, minimal, within the next day before starting a weakening trend.  This is quite possible but don’t buy into the intensity forecasts that keep Fred a hurricane throughout the next five days.  It won’t happen.