Evening Discussion on Tropical Storm Erika

[Stormsfury]

With Tropical Storm Erika developing earlier today, of course there are concerns of eventual path and strength. The path seems fairly certain forced along by a large scale upper-ridge north and northwest of Erika. From Northern Mexico up to about Corpus Christi looks to be the best window of strike, but this does not mean by any means, points north along the TX coast should let their guard down by any means.

Alright, let's get down to it. There are many concerns regarding Erika becoming a hurricane before landfall ... those concerns are well-warranted. Many parameters are being met for rapid intensification once the LLC becomes well-defined (which shouldn't take very long). RECON data just obtained at 26.6ºN, 85.4ºW obtained flight level winds (1500 ft) of 48.3 mph and a 1008 mb pressure.

1) High Oceanic Heat Content - SST's are in the 31-32ºC range.
2) Upper high over Erika allowing for good ventilation of the system ... particularly with the equatorial outflow channel, enhanced by a weakening ULL to its SSE in the Western Caribbean Sea.
3 Single-channel Outflow (on the equatorial side). The single-channel outflow may be divided into two subcategories based on direction of the outflow channel. Tropical cyclones with single-channel poleward outflow pattern generally intensify at an average maximum rate of 15 to 20 kt/6 hr. Tropical cyclones with single-channel equatorward outflow pattern generally intensify at an average maximum rate of 25 to 28 kt/6 hr. Dual-channel Outflow. Tropical cyclones with a dual-channel outflow pattern generally intensify at an average maximum rate of 35 kt/6 hr.
4) Cumulus Convection - The cumulus convection is increasing.
5) Weak Vertical Wind Shear

The SST's across the Gulf and across the expected path of Erika will remain anywhere between 30ºC-32ºC, plenty warm to support and allow for Erika to strength given the high SST's. However, there's a fly in the ointment, the SST's left in the wake of Claudette ... though not apparent on actual SST's, it is apparent deeper down where the waters were upwelled...

Sea-Surface Temperatures

Second Look

SST-Depth

Heat Content



Usually, with rapid intensification parameters involving SST's, usually you would need a sufficient deep layer of warm water (usually about 50m deep).

Otherwise, Erika should become a hurricane because there are many, many solid factors going with it ...

SF

[cycloneye]

Hey stormsfury that is a complete anaylisis with all the factors involved in favor and against.But I can tell you that you should be in a NWS office doing forecasts or even ay the TPC because what you are doing is like a proffesional met.

[Stormsfury]

Hey stormsfury that is a complete anaylisis with all the factors involved in favor and against.But I can tell you that you should be in a NWS office doing forecasts or even ay the TPC because what you are doing is like a proffesional met.

Thanks Cycloneye. Hopefully I'll be able to do these detailed analyses after my vacation's over with (tomorrow's the last day of vacation)

SF

[capecodder]

Thanks for a great discussion.


Richard

[mf_dolphin]

Well written SF! It's interesting that the models seem to be bring Erika a little more to the north. Is that a sign that the western high may not build as quickly as thought?

[ColdFront77]

How about this situation. What would a broad upper level high pressure system moving over and then south of Tropical Storm Erika do if anything to the movement of the system. Being broad, the upper level high would have good enough ventilation of the tropical system.

[Stormsfury]

How about this situation. What would a broad upper level high pressure system moving over and then south of Tropical Storm Erika do if anything to the movement of the system. Being broad, the upper level high would have good enough ventilation of the tropical system.

Actually, if you hypothetically have an upper high south of a tropical storm, that system will undergo westerly shear ...

SF

[ColdFront77]

Mike, I understand that fully.

Yes, hypothetically, (of course I am being hypotheically with my question[s] and comment[s]) an upper level high moving
south of Tropical Storm Erika would create westerly shear on the system.

My reference [above] is to a broad upper level high pressure being over Erika and building to the south of the system, not
just the upper level high moving south of the system.

[Stormsfury]

Sure, SF. I understand that if a hypothetically, (of course I am being hypotheically with my question and comment) an upper level high moving south of Tropical Storm Erika would create westerly shear on the system.

My reference [above] is to a broad upper level high pressure being over Erika and building to the south of the system, not just the upper level high moving south of the system.

Movement would be easterly much like a system riding the northern end of the Bermuda High (recurvature scenario) but a lot has to do with mid-level steering flow as well ...

SF

[ColdFront77]

So, my thinking if this took place (a broad upper level high moved south of Erika) it would not be able to continue westward, is correct. I thought that made sense.

I know I asked it the way I wanted to/the correct way initially.

Thank you, Mike.