Tropical Storm Joaquin: a Northeast storm? Or out to sea?
By now, I have to make the assumption that most of you have heard about the situation in the Atlantic regarding strengthening Tropical Storm Joaquin, and the fact that many models suggest it will be a threat to us in the Northeast over the next few days. However, nothing is particularly clear at this point, and some model solutions suggest that it will escape out to sea. Other solutions are quite funky, suggesting that Joaquin goes out to sea while a new storm batters the east coast. It will surely take a few days to figure this all out. I made several points yesterday and I will repeat them.
- Models are not gospel. There is an enormous range of solutions at this point representing a wide range of possibilities (as I will explain). Don’t feel alarmed if one model run (or ensemble run) shows a strong storm with high impacts coming your way.
- Although it will be difficult (but not impossible) for Joaquin to turn out to sea, there is no guarantee that there will be a backing trough able to turn the storm back to the northwest. Certainly, it doesn’t appear to be highly amplified like the situation with Hurricane Sandy in 2012.
- Mesoscale models (the GFDL and HWRF) are very unreliable with initially weak storms, and practically useless in extratropical transition and trough interaction situations.
- There is short term weather to be concerned about as well in the Northeast. A weak but moisture-laden system is expected to move across the region today through Thursday, with 3 to 6 inches of rain in spots. That is a virtually certain scenario and more worthy of our immediate concerns.
- Even if this was sure to be coming our way, it is still at least 4 to 5 days away and may be even longer before any Northeast impacts are felt due to the slow initial movement. The range of error at that time frame in standard practice is at least 150 to 200 miles either way. In this case, it is even higher. It is too early to talk specifics.
Joaquin is located to the east of the Bahamas, creeping slowly westward from its current position at 26.0N 70.7W. It has intensified this morning, and the latest Hurricane Hunters aircraft mission just left the storm finding a much lower pressure and stronger winds. It appears that sustained winds have increased to about 65 mph, with a central pressure down to about 989 mb. Although convection is still lacking on the north side of the storm, a well defined central dense overcast is sitting over the center. In fact, the aircraft even found hints of an eyewall forming, a clear indication of a strengthening storm. This is all in spite of about 20 to 25 knots of wind shear. As a result, I do believe Joaquin is on its way to becoming a hurricane, with major hurricane intensity not out of the question.
What the Models Say
This is an extremely complicated forecast due to the presence of Joaquin, 99L (a weak tropical low in the Gulf), former Ida (which may itself regenerate), a blocking ridge and a frontal boundary. Confidence in the track has dropped significantly in the last 24 hours. Yesterday, it appeared we had at least a decent handle on the storm. However, the range of possibilities has increased dramatically. In my opinion, there are at least 5 possibilities on the table:
Scenario 1: Bahamas and Southeast (10% chance)
The 12Z European model – normally a quite reliable model – came up with a surprising solution today. It strengthens Joaquin into a major hurricane, slamming into the Bahamas at Category 3 or 4 intensity ahead of the trough. However, despite undertaking a partial phase with the trough, Joaquin breaks free (possibly with the help of Ida) and turns out to sea, possibly threatening Bermuda along the way, and a new system forms off the east coast and drenches the entire east coast. I think a more likely solution in this scenario would be that Joaquin phases into the bottom of the trough fully and moves closer to Florida, possibly making landfall in Florida or the southeast US coast. No model currently suggests that possibility, but I feel it is more reasonable than the ECMWF solution looking at the image below. Regardless, I think it is unlikely, but more reasonable than at this time yesterday.
Scenario 2: Direct Mid-Atlantic hit (15% chance)
The notoriously unreliable HWRF suggests this possibility, along with the fairly unreliable CMC model and earlier ECMWF runs. This is a bad scenario for those in the Mid-Atlantic, particularly from North Carolina to New Jersey. In this case, the initial phase does not happen and Joaquin starts moving northward to the east of the Bahamas. However, the Southeast trough amplifies a bit later and allows a recurve westward for Joaquin. It would then likely make landfall between Cape Hatteras and Cape May as a hurricane, before either racing inland or looping back over water. This would be a bad scenario for many, with the 12Z HWRF showing a highly unlikely scenario which would be catastrophic for Hampton Roads.
Scenario 3: Indirect Mid-Atlantic and Northeast hit (30% chance)
This scenario is supported by the GFS and partially supported by the ECMWF, but may require some help from Ida (which is itself regenerating and may become a tropical storm once again. In this scenario, Joaquin continues westward in a similar fashion as Scenario 1 and tries to merge with the trough as above. However, it does not phase and remains distinct in the upper levels. Concurrently, Ida also begins a partial phase with Joaquin, resulting in a “squeeze play” east of the Bahamas. Ultimately, Joaquin starts to go out to sea, absorbing Ida in the process, but much of its energy is shifted to the ex-99L low in the Southeast. That low then emerges off the Carolina coast and may develop into a system (maybe another tropical cyclone?) in its own right, which results in very heavy rain, wind and waves in the US east coast.
Scenario 4: Direct Northeast hit (25% chance)
For places from the New York City metropolitan area to northern New England, this is a worst case scenario. It doesn’t have any significant model support at this time, but the larger-scale setup still would easily allow this to happen with some model ensembles supporting it. In this scenario, Joaquin begins a northerly turn near or east of the Bahamas, likely as a strong hurricane. It then tracks northward, likely at high speed, this weekend before slowing down due to the blocking ridge to the north and east. In addition, there is no trough able to capture Joaquin and send it inland like with Sandy. As a result, Joaquin makes landfall somewhere between Maine and northern New Jersey sometime between Sunday and Tuesday of next week. Cold water and shear would likely weaken Joaquin, but it may still be a formidable system at that time.
Scenario 5: Out to Sea (20% chance)
Unless you live in Bermuda, this is the best case scenario. The GFS and ECMWF have started to lean in this direction, but in both cases have a funky result. In this case, supported only by the GFDL and some ensembles, Joaquin strengthens in the weak steering currents east of the Bahamas, and does not interact with the ex-99L trough. Ida may or may not interact with Joaquin, but ultimately the ridge either builds back in to block the trough connection or a new trough forms in the central Atlantic. Either way, Joaquin heads back out to sea, although Bermuda could be at significant risk of impacts as a result. This would have to happen at a low latitude, since the Newfoundland ridge extends down to about 35N latitude.
The level of confidence in the forecast has decreased markedly today compared to yesterday. However, it is still quite likely that a heavy rain event – at least – is in store for most of the Northeast, whether or not it is directly or indirectly attributed to Joaquin. The other elements are far less certain, but must be watched closely. Regardless, the combination of the current low pressure system and frontal boundary, ex-99L and Gulf moisture, Joaquin and any spin-off lows could easily result in 6 to 9 inches of rainfall for the entire area from the North Carolina coast to Atlantic Canada west to the Appalachians and St. Lawrence Valley. However, I still believe that could be conservative, and amounts over a foot (as high as 15 to 20 inches) are not out of the question for some areas.
We must continue to keep a close eye on the situation, but we can’t be comparing this to Sandy or other storms yet. It is way too soon, and the situation is far too fluid for any of the scenarios to be locked in. We must be vigilant but calm at this stage, even though it is certainly possible that a high impact weather situation will take place in the next few days.
Forecaster Craig Ceecee