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PSUBlizzicane2007

Tropical Storm Erika

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Almost a naked swirl. We'll see what happens today

 

 

Not much is going to happen until the shear lets up and it finishes eating all the SAL to it's north and west.

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I posted this elsewhere, but I'll reiterate: "While mid- and upper-level shear has relaxed over the system, the strong low-level easterlies have continued to prevent convection from organizing near the center overnight, during the nighttime convective maximum. The fact that Erika hasn't strengthened will only hurt it over the next few days as it passes near the TUTT axis and continues to deal with stable air, plus less energy for latent heat of condensation thanks to Danny's impact on the sea surface temperature profile. Models don't do well with these weak systems, and given how Erika looks now, its center becoming even more dislocated from the convection (on latest visible imagery) is a death sentence for such a weak system.

 

Unless it can regenerate convection within the next 12 hours or so, Erika will likely weaken to a depression and then open up into a wave near the islands, as the GFS and the ECMWF ensembles have indicated for some time (the fact that the latest operational ECMWF keeps Erika intact doesn't mean much, as it differs significantly from its ensembles). In these cases, trust the mean of the global ensembles--especially that of the ECMWF ensembles--more than individual operational runs. Given that the NHC is still unclear about its intensity forecast even within three days, there is at least an equal chance that Erika will dissipate within the said time frame.

 

I'm willing to place a bet that Erika won't last more than another day and that it may have already weakened to a depression, considering its disorganization and meager convective pattern on satellite. ... As I mentioned earlier, all the strengthening occurs beyond three days, when forecasting errors increase significantly and confidence drops precipitously." The dynamical (12Z) GFDL and HWRF models have continued to lower their intensity expectations within three days, consistent with trends over the past few days. They show Erika basically remaining steady through 72 hours, even hinting at some weakening in the meantime.

 

Furthermore, "Also, some people believe that even if it opens into a wave, ex-Erika can still regenerate in the Bahamas, the eastern Gulf, or the Straits of Florida. There are several major problems with this hypothesis. 1) You would need a well-defined area of vorticity left. If Erika were to degenerate into a dry wave for several days, it would lose much of the convection-driven vorticity needed to sustain a low pressure center. 2) When you're back to square one--with a system having to resume its life cycle from the beginning--you will need favorable conditions in place. If you're dealing with a dried-out wave, you will need MUCH more favorable conditions in place, because you're starting out with less of a system. Currently, none of the reliable models indicates that conditions around the FL peninsula or in the eastern Gulf will be favorable for rapid development, hence the NHC's call for gradual intensification by day five, assuming an intact Erika. 3) A weaker ex-Erika in the short term would move farther south and west with the low-level trade winds, meaning significant land interaction with mountainous Puerto Rico, Hispaniola, and Cuba."

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Latest intensity estimates have actually come up but indicating a shear environment

2015AUG25 121500 2.7 1006.8 39.0 2.3 2.3 2.3 NO LIMIT ON OFF -11.36 -31.97 CRVBND N/A -3.4 14.79 50.31 FCST GOES13 33.2
2015AUG25 124500 2.7 1006.7 39.0 2.3 2.3 2.3 NO LIMIT ON OFF -5.16 -24.86 CRVBND N/A -3.4 15.05 50.42 FCST GOES13 33.3
2015AUG25 131500 2.6 1007.8 37.0 2.3 2.5 2.5 NO LIMIT ON OFF 10.44 -22.16 SHEAR N/A -3.4 15.08 50.53 FCST GOES13 33.2

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The Euro is an awful run, open wave in the Southern Bahamas in three-four days.

But it's most likely correct. I'd like to see someone make a credible argument against the ECMWF and especially its ensembles. A system like Erika, once an open wave, will have trouble regenerating without a well-defined area of vorticity, unless environmental conditions are absolutely perfect. Even then, organization would be slow at best, resulting in a weak to moderate tropical storm at most moving into South FL. Nevertheless, I've been consistently saying that Erika would eventually open up and move westward into the Greater Antilles, and it remains the most likely scenario now. I'd love to see someone make a decent counterargument that argues for an intact Erika or a regenerating Erika that could reach something stronger than a middling TS.

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I agree, the  complete lack of support from the global models is a rather telling sign, I never trust the GFDL and HWRF unless there is least a bit of support for their solutions elsewhere.

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The 12z run just started running on instantwxmaps. Just verify that it is not yesterday's run.

Today's run is out to 132, not even one closed isobar.

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I'd love to see someone make a decent counterargument that argues for ......a regenerating Erika that could reach something stronger than a middling TS.

 

One word:   Andrew

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Yeah, I remember Andrew being sheared almost apart and then boom shear relaxed and he exploded.  Once he got strong his track was a perfect due west.

Insert generic "every storm is different" comment here. It's a crapshoot. 

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Erika looking quite good late this afternoon. Outflow is improving and the IR loop seems to indicate that shear might be relaxing some. You can see that the she is still being restricted some on the Northern semi-circle. That seems to coincide with the strongest shear axis per this graphic.

 

wg8sht.GIF

 

vis_lalo-animated.gif

 

rb_lalo-animated.gif

 

wv_lalo-animated.gif

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Question: Why do the HWRF and GFDL models run beyond day three, when their reliability on track and intensity becomes atrocious? Shouldn't their runs be shortened to short-term forecasting?

The HWRF had more accurate track verification at 96 hours than the NHC last year (as well as 36-72 hours). It is certainly not "atrocious", and while other guidance argues against Erika's intact survival we have not even reached the forecasted points of reintensification; it's a little early to be calling it wrong.

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18z Spaghetti models continue to show a steady state over the next few days and then strengthening beyond day 3.

 

 

 

The forecast track would suggest an impact in the Bahamas and a close call for Florida.

 

 

not liking how the models keep erika so weak for so long. we saw what happened when danny was beat down by shear and dry air.

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not liking how the models keep erika so weak for so long. we saw what happened when danny was beat down by shear and dry air.

Maybe I am missing something but I don't see a ton of dry air around. The SAL out ahead of it continues to slide West in tandem with Erika. Also, I think a majority of the models are indicating interaction with the islands more than anything else. Shear doesn't appear to be a problem moving forward unless again I am missing something.

 

wv_lalo-animated.gif

 

wg8sht.GIF

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Intensity estimates bumping up the last three passes

 

2015AUG25 174500  2.4 1009.4  34.0  2.2 2.5 2.5  NO LIMIT   ON  OFF  -66.16 -40.67  IRRCDO   N/A   -3.4   15.38   51.74  FCST   GOES13 32.2
2015AUG25 181500  2.4 1009.4  34.0  2.4 2.7 2.7  NO LIMIT  OFF  OFF  -65.36 -45.17  IRRCDO   N/A   -3.4   15.42   51.87  FCST   GOES13 32.1
2015AUG25 184500  2.4 1009.4  34.0  2.4 2.7 2.9  0.5T/hour OFF  OFF  -63.76 -47.90  IRRCDO   N/A   -3.4   15.45   52.01  FCST   GOES13 32.0

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Maybe I am missing something but I don't see a ton of dry air around. The SAL out ahead of it continues to slide West in tandem with Erika. Also, I think a majority of the models are indicating interaction with the islands more than anything else. Shear doesn't appear to be a problem moving forward unless again I am missing something.

 

 

 

 

you are right about the dry air, the shear to the north worries me a bit, but NHC has erika a 60mph TS by tomorrow.  and if current trends hold overnight into the dmax i will feel a bit better.  the overall structure has improved a great deal over the last few hrs.

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