Erika must be watched, but NOT time to panic by any means

Good afternoon.

Not much has changed really since the last forecast update on Tuesday regarding Tropical Storm Erika. As expected, it remains a disorganized storm in the NE Caribbean, affected by significant wind shear. The upper-level circulation is more vigorous, and despite its very poor satellite presentation, sustained winds are reported to be around 50 mph currently.

Current and Short Term Situation: Struggling in the Caribbean

Wind shear remains a potential hindrance and should continue to affect Erika for the next couple days, so it should remain a relatively weak tropical storm at least through Saturday. In addition, the center reformation farther south results in more land interaction, which could very well result in dissipation, especially if Erika follows the southern end of the new cone over Hispaniola (with its very high mountains especially in the south and southwest) and eastern Cuba. Tropical storm conditions are currently ongoing in parts of the Leeward Islands and are possible (or likely) through most of the Greater Antilles and the southeastern Bahamas between now and Saturday, especially in exposed locations and higher elevations.

Should Erika track farther north, over water for most of its short term life, it would be affected to a much lesser degree and would have a better chance at strengthening in the medium term. Overall, models are in fairly good agreement with a track either along the spine of the Greater Antilles or just to the north. Confidence in the short term track is Very High.

Short term forecast for Erika, showing where tropical storm force winds are possible through Saturday. (My map)

Short term forecast for Erika, showing where tropical storm force winds are possible through Saturday. (My map)

Long Term Situation: We Must Watch

By late Saturday, the center of Erika should either be in the southeastern Bahamas or near/north of eastern Cuba. Uncertainty becomes the name of the game once we get to Sunday and into next week, with models not in real agreement at all. Some models dissipate the storm before then, others send it into Florida, others stall it out near the Bahamas or off the Carolina coast and others take it out to sea. Given the more southern position, I believe the Gulf of Mexico scenario is not entirely impossible either, although Erika would have to survive as a weak storm to be in that position. In general, a stronger storm in the shorter term recurves it sooner, while a weaker storm carries westward more and more. The 12Z ensemble run and my scenarios (explained in greater detail) are below.

Model run plots for Erika in the longer range. Note the clustering close to the east coast of Florida, but uncertainty beyond. (Map from SFWMD)

Model run plots for Erika in the longer range. Note the clustering close to the east coast of Florida, but uncertainty beyond. (Map from SFWMD)

Long range track scenario map for Erika beyond Saturday. Notice the high uncertainty. (My map)

Long range track scenario map for Erika beyond Saturday. Notice the high uncertainty. (My map)

Scenario 1: Out to sea

Note that this is more like my old Scenario 2, since the previous Scenario 1 (near Bermuda) no longer is expected. Many of the ensemble runs continue to send Erika safely out to sea as the trough opens up a broad weakness in the Bermuda High, roughly along the Gulf Stream, after impacting the Bahamas and brushing the east coast of Florida. However, the more southerly initial position makes me believe this is becoming less likely, as this would be more likely with a stronger storm sooner. I hence give it a 15% chance of this occurring. Land impacts would be dependent on intensity for the Bahamas, but for the most part limited to high surf and rip currents along the east coast beaches.

Scenario 2: Just offshore the East Coast

This has more significant model support and assumes the ridge weakens to a lesser degree, while the trough steers Erika just offshore the east coast, possibly over the Outer Banks and other exposed headlands, before the ridge rebuilds as expected by the middle of next week. It is somewhat like the GFS and ECMWF runs and supported by numerous ensembles. This would likely have significant impacts to coastal communities in the Mid-Atlantic and Northeast, with much lesser impacts inland, although it is highly dependent on the size and intensity of the storm at that time. If the ridge manages to rebuild after Erika starts to move offshore, it could meander just offshore as well, leading to many days of uncertain impacts and rough surf. I give it a 20% chance of occurring.

Scenario 3: East Coast landfall

This could happen in one of three ways. The more likely situation is similar to the left-most ensembles and earlier model runs in that Erika remains very close to (possibly right on) the Florida east coast, and starts to recurve but hits the coastline between Cape Hatteras and Savannah, and possibly stalls out if the ridge rebuilds or makes a hard turn back over water. A second possibility is that Erika remains just off the Southeast coast, and the ridge rebuilds and forces it westward (think Dora in 1964) between roughly Wilmington, NC and Jacksonville, FL. The most recent CMC model run (one of the least reliable models) suggested that Erika will remain offshore for a while but move inland (think Sandy) not far from New York City.

It is plausible but not terribly likely as it would require a rapidly rebuilding ridge to the north and an inverted trough concurrently, which is not a typical setup for early September and most models rebuild the ridge much farther south. Given the favorable conditions expected near the Bahamas, it is quite likely that Erika would be a hurricane at any of these landfalls. For the Northeast, it would be important to watch closely in the next few days, although preparation is not necessary at this time. For those in Florida, early preparations would be useful right now, but major preparations are not necessary at least in the short term. Overall, I give this scenario a 15% chance of taking place.

Scenario 4: Florida landfall

This scenario was hinted by many models on Tuesday and Wednesday, then practically eliminated yesterday before re-emerging on the 00Z ECMWF (very reliable), some 12Z ensembles and the 06Z NAVGEM (not a terribly reliable model either). Again, this could happen one of two ways. The more likely scenario leading to a Florida landfall would be for the track to remain far enough west to either go clearly into South Florida or into Southwest Florida as it begins a recurve (similar to Fay 2008). An alternate scenario is for the storm to go into the Scenario 3 position, but get blocked by the rebuilding ridge earlier than expected, resulting in Erika being shunted westward into the Florida peninsula. Given the more southerly initial position, these are both very reasonable possibilities. If it emerges in the Gulf, a second Florida landfall on the Panhandle is most likely. I give this a 15% chance of occurring.

Scenario 5: Gulf of Mexico threat

Although no models and virtually no ensembles show this run, I still think it is not entirely impossible, especially if Erika remains weak (but does not dissipate) through Saturday. Erika would have to thread the needle to avoid as much land interaction as possible (such as remaining on the southernmost edge of the cone, missing most of Hispaniola) and then eastern Cuba is not as mountainous so it may be able to survive into the Florida Straits. Since Erika would likely be very weak initially, its intensity in the Gulf of Mexico would be very uncertain as a result. Despite the lack of model guidance supporting such, I have increased it to a 10% chance of taking place.

Scenario 6: Short term dissipation

Erika is not a very well organized storm and very well may not be able to survive over land or even over water in high shear. Some models actually dissipate it, and that is not unreasonable by any means. Such is especially likely if Erika traverses the highest elevations of Hispaniola, where mountains as high as 10,000 feet in height can tear apart even strong hurricanes. Without a surface circulation, it is uncertain if Erika would be able to re-develop at all once clear of the Greater Antilles. As a very reasonable possibility, I give it a 25% chance of such.

Conclusion

This is definitely not time to panic, especially in the Northeast. While the CMC model was stunning, it is just one model and a less reliable one at that which makes little sense for the time of year. That said, erratic tracks with loops and sharp turns are very likely early next week – assuming Erika survives. Those in Florida especially should be closely monitoring Erika and may want to take the earliest preparation steps. Regardless, it will be a very interesting week ahead.

Forecaster Craig Ceecee (@EternalWeather1)

Featured image tweeted from NWS Columbia, SC (@NWSColumbia)

Leave a Reply