*BLOG* Tropical Storm Erika

11PM advisory

Latest GFS brings this storm inland into the Carolinas.

Hey guys here is my take on Erikas current status.  At first glance it may look like she looks healthy but in fact not so much.  She has a lot to contend with between now and until she gets into the Bahamas.  


As you can see there is a really nice convection which may lead you to believe she is healthy and poss strengthening.  However; the entire system is decoupled from the low level center(LLC) and the spin in the mid and upper levels which means we prob wont see much strengthening until the spin in the diff layers of the atmosphere becomes more vertically stacked as well as the LLC moves into a more favorable environment.  Let me explain.  

First image is 850mb vorticity(spin)  Notice the center of circulation is shifted S of the LLC.  Second image is 500mb vorticity and its center of circulation is S and well east.
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What you want to see is the centers of vorticity centered over the same Lat and Longitude as the LLC.  So why does the convection look so good at the moment on the Sat loop?  The next image is the wind shear map followed by the upper level divergence map.  On the wind shear map, however, are also the winds in the upper levels (blue arrows).  Notice how over the top of Ericka's convection center you have one arrow moving E to NE, and the other moving E to SE.  The winds over top of Erika are diverging or moving away from each other.  This forces the air in the lower levels to rise to replace the air that has moved out of the upper levels.  Rising air equals convection and thunderstorms.  In order for a tropical system to strengthen you want those upper level winds to move away from(diverge) in all 4 quadrants from th center of circulation.  You can see clearly that is not the case here.  Instead you are only getting divergence in the NE and SE quadrants.  But again there is divergence aloft so you get good convection underneath, but its to the S and E of the LLC.
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The next 3 days will be interesting to see how Erika hold up.  Again looking at the wind shear map I have above notice I outlined in black the wind shear contours.  They indicate that Erika has to pass through a gauntlet of mild-mod wind shear(10-20Kts) before she enters the area of the Bahamas and Turks and Caicos where the wind shear drops off.  She also still has some dry air to contend with out in front of her to the W and NW(see below)
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So for now because there is a decoupling in the various layers of the atmosphere, dry air, some wind shear, and the currently unknown interactions with the islands out ahead of her the models will cont to waffle a bit in their solns beyond the 3-5day.  Things should stat to become clearer as we move into the next 3  days or so.  One thing I will say is when I look at the upper level pattern developing over the NE and Atlantic and even out west I get concerned that a track that moves Erika off the coast N and E followed by a recurve back to the NW towards the coast again is something Im monitoring closely.  I have some things saved to support that idea and will try to postit later as I have run out of time this morning.  FINALLY something interesting to track....Its good to be back.

the 6zgfs has Erika off the east coast for more than a week...

96hrs day 4

192hrs day 8

312hrs day 13
incredible!! if that happens

scott nice to hear from you and nice write up. i didn't think Erika was going to make it but when she hits the florida coast she has no where to go and that is concerning. steering flow very weak in s/e U.S. with ridge strengthening over north east. what she does and how strong she gets is any ones guess right now. it is going to be awhile before we are rid of her.

6z gfs has her meander off the GA and SC coast brushes each coast but not making landfall. Looks like a cat 2 possibly cat 3 cane on this run. Jyust meanders there fir days then slowly drifts ene and then ots and blows up. One model run and I am sure there wil be lots of changes.

algae888 wrote:scott nice to hear from you and nice write up. i didn't think Erika was going to make it but when she hits the florida coast she has no where to go and that is concerning. steering flow very weak in s/e U.S. with ridge strengthening over north east. what she does and how strong she gets is any ones guess right now.  it is going to be awhile before we are rid of her.

Yeah Al. With so many variables between now and when she gets into the Bahamas we most likely will see solns cont to waffle. I will be monitoring the trends at 500mb at when and how the current mid level trough moves into the Canadian maritime, followed by the ridge building into the NE in its place, and IF the ridge builds in strong enough does it link up with the SW Atlantic ridge currently steering Erika? Combine all that with the timing, intensity, track, etc of Erika as she continues her W NW journey into the Bahamas. Fun times ahead!!

Sroc,
The summer hiatus is over huh?Great to hear from u Paisan and glad to see you posting. Analysis is always much appreciated, in depth and educational besides awesome accurate work.

Can not go beyond a few days with these canes and we should learn from past experience how quickly they can change. She is a biag that will make it thought the Bahamas and then say Hello as she enters into the area where she can strengthen, reorganize. Time will tell and the models will waffle big time

Again a long way off and by no means am I saying this happens but a Sandy esque track, ie; once she reaches the SE coast region the track shifts NE followed by recurve back NW.  Yesterdays 12z Euro is my example.  The image below is at hr240 so take with a grain of salt.  My point here is that the possibility exists with the upper level pattern.   IF the ridge in the NE traps Erika underneath and she meanders off the coast like several models are indicated (exactly where and at what intensity unimportant now)......
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Look at the ridge building into the NE.  As the long wave trough pushes east across the country is will force the ridge to build over top into eastern canada. This could lead to a strong blocking signature ala HP to the NE esp if the ridge over top connects to the SW Atlantic ridge. As the trough out west approaches the coast in theory could start to pull Erika back to the coast similar to the way Sandy was pulled back.  

Again not likely to happen at this time. but is still a plausable soln given the pattern. I suppose, like looking at a good winter storm in the LR, we still have to monitor the trends in the upper levels over time, and monitor the details of Erika in the short term as she continues through the dry air, shear, and interactions with the islands between the eastern Caribean and the Bahamas.

Wow, sroc hey! The fact you mention even the possibility of a Sandy track is downright scary with a storm looking to be much more powerful, we def do not need a storm the same or worse than Sandy. No not getting my anxiety on as I understand the chances like you said are not high but its still something to wonder about and we will have a while to contend with her and who she may or may not slam. I personally think she has been a trouper and will make it through the rough area, off the SE coast I expect to see a very strong hurricane develop. Where it goes from there is too far out. But the possibility or a NW recurve is unsettling. IF something were to head up this way are we talking a week, two weeks? With that stall looks like a while. Anyways hope to get more insights from you, your very knowledgable and I'd like to see what Frank says in regards to your thoughts. He put our area at 20%, hey that is means to at least watch this thing. We did get a little strengthening to 50mph this morning which is not what NHC thought last night.

algae888 wrote:scott nice to hear from you and nice write up. i didn't think Erika was going to make it but when she hits the florida coast she has no where to go and that is concerning. steering flow very weak in s/e U.S. with ridge strengthening over north east. what she does and how strong she gets is any ones guess right now.  it is going to be awhile before we are rid of her.

See Al I told you these things can and do make surprises more so than the winter systems (errm well Juno a exception), yet a lot can still change, got one more hostile area to go through but if the blowup of convection keeps up she will make it as she is still moving pretty fast at 16mph, I also read that she is wobbling south a bit which would take her even further west possibly, not go b a good look off SE coast, anyone on EC should put some preps in place IMO, I am sure at least some of us have interests all up and down the EC.

algae888 wrote:the 6zgfs has Erika off the east coast for more than a week...

96hrs day 4

192hrs day 8

312hrs day 13
incredible!! if that happens

That will drive me loco if it happens lol, wheres she going...nowhere! Great so what now lol, its all wait and see.

Hey there Jman! Good to be back...just an FYI if it did take a hook towards the coast esp up by us most likely would weaken significantly before landfall as the water temps North of Cape Hatt cool significantly.

True but it still could wack a punch, we cant even handle cat 1 winds, if it were a cat 3 it would probably weaken to a strong TS or maybe a 1, but that's neither here nor there as of right now we have much time to pass still b4 we know much more. Models are all over the place as usual but have a general idea of a strong hurricane off SE coast by end of weekend. Once there I think we will have a better idea.

sroc4 wrote:Hey there Jman!  Good to be back...just an FYI if it did take a hook towards the coast esp up by us most likely would weaken significantly before landfall as the water temps North of Cape Hatt cool significantly.  

sroc, aren't they warmer than usual though off the coast, I saw a map from wxbell that showed SSTS much higher than normal.

Jman just saw the Southward shift of Erika. She is now forecast to skirt the northern coast of Hispaniola. Yesterday she was forecast to pass north of there. If she does take a direct path over that island it could weaken her substantially and probably end up Crossing Florida heading into the Gulf. The next 48 hours are criticalto what happens with Erika. Will be interesting to see what the model show today

Fwiw the 12 znam takes her over Hispaniola and weakens her substantially, probably a depression at that time, as she heads between Cuba and the Bahamas and then strengthens before hitting the southernmost Florida coast.

I posted below NHC's discussion. The gist of it is the low level center is dislocated well south and west of where the convection is. Thus, an LLC found further south means Erika could run into Hispaniola. This would weaken the storm significantly and likely prevent it from coming up the coast.

National Hurricane Center wrote:Erika is not well organized at this time. Although deep convection
increased overnight and early today during the diurnal maximum,
with considerable lightning activity, banding features were
lacking. The convection is also not well organized on the
Guadeloupe radar imagery. Recent high-resolution visible imagery
shows the low-level center becoming exposed, again, to the
northwest of the main area of thunderstorms. Data from the aircraft
do not indicate any strengthening, and the initial intensity is kept
at 45 kt.

The latest aircraft fixes show that the center has apparently
reformed farther to the south of previous estimates. With some
adjustments to the previous location, the initial motion estimate is
kept at 270/14. For the next few days, Erika should move
west-northwestward to the south of a mid-level subtropical ridge.
Later in the forecast period, as the tropical cyclone nears the
western periphery of the ridge, a turn to the northwest and
north-northwest should occur. However there is uncertainty as to
how soon and how sharp this turn will take place. The future track
of Erika is also dependent on its intensity, with a weaker system
likely to move more to the west and a stronger cyclone more to the
east. There is substantial spread in the track models at days 3 to
5, partially due to differences in model-predicted intensity. The
official track forecast has been shifted to the left of the previous
one mainly due to the adjustment in the current center position.
This is close to the model consensus.

As expected, Erika is being disrupted by an unfavorable atmospheric
environment, and this disruption is expected to continue for the
next couple of days. No significant strengthening is expected until
later in the forecast period. In addition, with the reformation of
the center to the south of the previous track, the likelihood of
interaction with the land mass of Hispaniola has increased. This
has implications for Hispaniola, of course, but also for the track
and intensity of Erika after that. In short, potential impacts for
the Bahamas and beyond are unusually uncertain.

@Scott - nice write up and glad to see you out of hibernation. One thing I did not see you mention is the ULL in the southeast. There have been some sloppy phases between the ULL and Erika on previous model runs, but last night's GFS showed a cleaner phase which allowed Erika to move in over land. In a way, this could also turn into a Rex Block scenario.

Yes Hispanolia is the KOD for tropics, but NHC still has her gain hurricane status near FL, wait and see....I trust you guys are keeping a good idea of what is going on.

12z gfs also has her running into Hispaniola run still early but it definitely weakened her

Frank_Wx wrote:@Scott - nice write up and glad to see you out of hibernation. One thing I did not see you mention is the ULL in the southeast. There have been some sloppy phases between the ULL and Erika on previous model runs, but last night's GFS showed a cleaner phase which allowed Erika to move in over land. In a way, this could also turn into a Rex Block scenario.

Yeah I actually plan on discussing that after seeing the 12z GFS today.  Its a splits off the trough currently in the east and should act to prevent it from entering the GOM and provide ventelation in the upper levels for strengthening once it reaches the SE coast.  Question is what is left to work with by that point

Up to hour 153 on the 12z GFS Erika doesn't get below 1000 Mb. It basically rides the whole Florida coastline into South Carolina so if this is correct probably a weak to moderate tropical storm

At hr 195 she is still off the sc coast. One thing that is becoming clear is that she is not going away anytime soon

Still sitting off the coast of SC at hour 210 on the 12z GFS.

Wow, the 12z Canadian shows a NC landfall and it looks like at least a cat 2.

wxbell is slow, but hearing the 12z Canadian has a cat 2 landfall in NJ.