Tropical Storm Erika

[wxmx]

Yes, latest intermediate advisory has it at 16.5N (was 16.8N @ 5am). Even with all the strong convection all night, the low level circulation got a little more disorganized.

[dtk]

The GGEM and Euro with the 4dvar res are better equipped than the GFS in showing TC intensity. And then I'd still favor the high res TC models. That's what they were designed for.

GGEM no longer runs 4DVar, as it was replaced earlier this year with 4D EnVar (there is a significant difference).  4DDA (4DVar and 4DEnVar) will not necessarily make much of a difference in forecasting intensity, since there is no attempt to initialize the actual structure (complications with assimilating cloudy/precipitating MW/IR radiances, lack of other data, issues of representativeness).

 

As an example, here is a comparison of last night's 00z GFS forecast using the 13km GFS from operations (top) and experimental 4D EnVar-based initialization (bottom):

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/2Dgfsfcst/PSPR_naf138_t00z.png

 

Then changes in DA are substantial yet these forecasts end up similar.  Another thing to keep in mind is that the GFS uses TC initialization (combination of relocation and assimilation of advisory min pressure), whereas GGEM and ECWMF do not.  This is why you will often see very disjointed/too weak systems in the EC initial conditions.

[PSUBlizzicane2007]

So the most recent Euro moves Erika into a loop by having it make landfall in South Florida, going into the Gulf, making landfall again near the Big Bend of Florida, going off the coast near GA/SC, then moving south off the east coast of Florida.

Meanwhile the GFS is trying to move it as a strong hurricane directly north into a pretty strong Ridge off the east coast of GA which makes no sense.

[BTRWx]

So the most recent Euro moves Erika into a loop by having it make landfall in South Florida, going into the Gulf, making landfall again near the Big Bend of Florida, going off the coast near GA/SC, then moving south off the east coast of Florida.

Meanwhile the GFS is trying to move it as a strong hurricane directly north into a pretty strong Ridge off the east coast of GA which makes no sense.

There's going to be some upset coastal residents if these models can't hone in on better solutions soon.

[IsentropicLift]

Looks like the center may have reformed further South and the 12z hurricane guidance has responded. All models now take the core over Puerto Rico and then very close to Hispaniola. This track will keep Erika closer to the shear axis over the Caribbean longer and in very close proximity to the mountainous terrain of the Dominican Republic. Should the center survive the trip and make it into the Caribbean, it has been very well advertised that conditions will be favorable for development. The fact that models now don't show much improvement until off the Florida coast is not surprising. What is left of the center could harmlessly drift into Southern Florida bringing some beneficial rains, or get completely hung up over the DR and dissipate. The GFS, GGEM and UKMET all show the center surviving with intensification as the system pulls North towards the Carolina coast early next week. I am not buying the sharp recurve out to sea at this time and I believe a track similar to Irene is quite possible. Not the sexiest of outcomes for the tropical snobs, but it would have the potential to cause a lot of flooding up and down the East coast. With that ridge moving overhead late in period, I would expect Erika to eventually stall near the Mid-Atlantic coast and rain itself out, increasing potential for major flooding.

 

 

[WhiteoutWX]

People should probably take a step back from the 3+ day model runs and look at the current situation first. The current organization and expected near-term conditions mean we have no clue what shape the circulation will be in by the time it reaches the Bahamas. I believe this will pass much closer to Hisponola (possibly right over it) than models are indicating. The shear direction plus dry air to the north both argue for continued deep convection along and south of the low level center. Given that this is still a weak system this may be able to tug the circulation south enough over time to track it right through Puerto Rico and Hispanola, and this type of subtle but constant forcing isn't always handled well by the models. I'd argue that Erika might be in worse shape in 3 days than most models are advertising. Will be interesting to see how it unfolds!

 

I'll just repost since everyone was too busy looking at 7 day model runs last night. 

[IsentropicLift]

ADT still initializing the center well NW of the deepest convection.

 

[IsentropicLift]

I'll just repost since everyone was too busy looking at 7 day model runs last night. 

This is a weather enthusiast board. We are here to discuss weather not give forecasts on the 6:00 news. Obviously this board is full of mets but they do not deliver forecasts to the public in the same tone.

[DopplerWx]

ADT still initializing the center well NW of the deepest convection.

 

 

she is in the middle of the worst of the shear now and has a new batch of dry air coming in from the N, not a surprise.

[PSUBlizzicane2007]

Looks like the center may have reformed further South and the 12z hurricane guidance has responded. All models now take the core over Puerto Rico and then very close to Hispaniola. This track will keep Erika closer to the shear axis over the Caribbean longer and in very close proximity to the mountainous terrain of the Dominican Republic. Should the center survive the trip and make it into the Caribbean, it has been very well advertised that conditions will be favorable for development. The fact that models now don't show much improvement until off the Florida coast is not surprising. What is left of the center could harmlessly drift into Southern Florida bringing some beneficial rains, or get completely hung up over the DR and dissipate. The GFS, GGEM and UKMET all show the center surviving with intensification as the system pulls North towards the Carolina coast early next week. I am not buying the sharp recurve out to sea at this time and I believe a track similar to Irene is quite possible. Not the sexiest of outcomes for the tropical snobs, but it would have the potential to cause a lot of flooding up and down the East coast. With that ridge moving overhead late in period, I would expect Erika to eventually stall near the Mid-Atlantic coast and rain itself out, increasing potential for major flooding.

Just FYI those are early cycle guidance... The real runs of the GFS, etc. haven't completed yet.

[Ground Scouring]

I posted this elsewhere, but it might be worth reading: Despite shear, Erika has some very good upper-level support, with good outflow on the eastern and southern sides. CIMSS analysis shows strong upper-level divergence and ventilation, which, along with low-level convergence and high PWATs, are allowing convection to generate, keeping the system alive as we enter the unfavorable daytime hours, convection-wise. The upper-level "fanning" we are seeing could be an ominous indicator of what Erika could become over the Bahamas in just a few days, depending on its position relative to the upper-level anticyclone. The ECMWF and its ensembles have consistently shown a blocking pattern by days four through seven that would likely force even a fairly strong Erika somewhere over the FL peninsula or the GA coast (between the upper Keys and Savannah). I really don't buy the GFS-based guidance and GEFS members that show either a curve off the East Coast or a track farther north into the Carolinas. I still don't expect Erika to survive, however, given the center relocation and the stronger-than-forecast low-level easterlies that would bring the center over or just south of Puerto Rico and into Hispaniola. I still believe that the combined effects of Hispaniola and continuing short-term shear will kill it. However, if Erika somehow and unexpectedly survives, the western Bahamas and FL/GA will need to prepare for a possible hurricane impact. Even a weaker system tracking over the west side of the FL peninsula would bring heavy rainfall to areas that don't need it (i.e., Tampa Bay).

[IsentropicLift]

Just FYI those are early cycle guidance... The real runs of the GFS, etc. haven't completed yet.

Well obviously, but we have seen a significant shift South over the last few cycles. Yesterday the models were tightly clustered just NE of PR.

[DopplerWx]

I posted this elsewhere, but it might be worth reading: Despite shear, Erika has some very good upper-level support, with good outflow on the eastern and southern sides. CIMSS analysis shows strong upper-level divergence and ventilation, which, along with low-level convergence and high PWATs, are allowing convection to generate, keeping the system alive as we enter the unfavorable daytime hours, convection-wise. The upper-level "fanning" we are seeing could be an ominous indicator of what Erika could become over the Bahamas in just a few days, depending on its position relative to the upper-level anticyclone. The ECMWF and its ensembles have consistently shown a blocking pattern by days four through seven that would likely force even a fairly strong Erika somewhere over the FL peninsula or the GA coast (between the upper Keys and Savannah). I really don't buy the GFS-based guidance and GEFS members that show either a curve off the East Coast or a track farther north into the Carolinas. I still don't expect Erika to survive, however, given the center relocation and the stronger-than-forecast low-level easterlies that would bring the center over or just south of Puerto Rico and into Hispaniola. I still believe that the combined effects of Hispaniola and continuing short-term shear will kill it. However, if Erika somehow and unexpectedly survives, the western Bahamas and FL/GA will need to prepare for a possible hurricane impact. Even a weaker system tracking over the west side of the FL peninsula would bring heavy rainfall to areas that don't need it (i.e., Tampa Bay).

great analysis.  i expect we will see a naked llc sometime today and that should give us a good idea on the heading of the llc into PR and hisp.  she is in the middle of the worst of the shear zone now, and tonights dmax will be key in the heading, and overall survival of the system.

 

EDIT: and as i post that, the llc is exposed on visible. well NW of the convection.

[IsentropicLift]

Look how strong the anti-cyclone is to the North. This might end up going right into the Caribbean.

 

[Joe4alb]

I would believe that due to the fact this has remained relatively weak is why we have seen this more of a westerly progression with little northerly trajectory as previously forecasted. 

[dmartin29]

Can't spot a better place to post this. Move it or tell me where.

I have a home on the North Shore of Hispanola. There has been near drought conditions for a few months. I think I understand the underlying blocking pattern. Is Erika likely to “break” the pattern? When the Jet moves to a more typical northern track will we see some of the dry air move out? Thanks.

[IsentropicLift]

Just about every 09z SREF member has an intense storm near the FL coast in four days lol

 

[BTRWx]

Just about every 09z SREF member has an intense storm near the FL coast in four days lol

 

WPC supports that

[IsentropicLift]

The 12z GFS takes the center right over the DR tomorrow night. It does have a closed 500mb low surviving and managing to stay just offshore. 

[IsentropicLift]

Meanwhile Erika looks awful on IR. The diurnal minimum is certainly not doing it any favors. 

 

[IsentropicLift]

At 06z Saturday the GFS has a closed 500mb low with good vorticy near the Turks and Caicos. The mid-level center stays strong and that's probably why most models show a slow but steady reorganization beyond day 2.  

 

[calm_days]

 

Seemingly Erika would have to encounter the deep trough directly as with most recently, Arthur in 2014; sometimes a trough will lift out of the way, but this one is already firmly in the Gulf.

[OHweather]

Seemingly Erika would have to encounter the deep trough directly as with most recently, Arthur in 2014; sometimes a trough will lift out of the way, but this one is already firmly in the Gulf.

The trough over the Gulf could help enhance outflow down the road...the most immediate concern is the pretty good chance of the center getting disrupted by Hispaniola.

[SN_Lover]

Should start moving North at any time. Organizing rapidly. 

[Eastatlwx]

Should start moving North at any time. Organizing rapidly.

where are you getting this real time data?

[DopplerWx]

man, the outflow on erika is gorgeous.  if she can get going she will be a big storm for sure.

[IsentropicLift]

The end of the GFS takes the center from near Bermuda and places it near the 70/40 Benchmark <965mb 84 hours later. Deep trough building into the TN Valley. What a crazy solution, but they said that just under 3 years ago.

[CCHurricane]

The end of the GFS takes the center from near Bermuda and places it near the 70/40 Benchmark <965mb 84 hours later. Deep trough building into the TN Valley. What a crazy solution, but they said that just under 3 years ago.

Talking of crazy solutions, check out the Canadian...all of the east coast from Florida to New England would have to be on alert with that kind of track. 

[EasternUSWX]

Looks like center is trying to tuck back in and moved north a bit. 

 

[IsentropicLift]

Talking of crazy solutions, check out the Canadian...all of the east coast from Florida to New England would have to be on alert with that kind of track. 

Yeah, the GGEM dumps a lot of rain.