Hurricane Joaquin still a serious threat, despite model changes

Good afternoon.

There was a lot of discussion in the weather universe last night and this morning when models came out showing Joaquin going out to sea to a much greater extent, when only the European model showed it consistently for the last couple days. However, it is important to remember that there are still ensembles and operational model runs that bring Joaquin ashore somewhere between the Carolinas and New England, likely still at hurricane intensity. Other model runs bring the storm dangerously close to the Northeast coast even if it keeps it offshore. As a result, it is far too soon to put the guard down or say all clear. Landfall remains a distinct possibility (although lower than yesterday) and model runs can and do change on a whim as we have seen, especially with such a difficult forecast. In addition, the frontal boundary and other systems may continue to produce heavy rain and flooding across much of the region, especially in the Mid-Atlantic (and catastrophic flooding is possible in the Carolinas and Virginia, even if Joaquin remains well offshore).

Current Situation

This is an extremely volatile situation in the central Bahamas which are currently feeling the brunt of Joaquin’s fury. Joaquin has continued to intensify through the night and morning, and is now an extremely dangerous Category 4 hurricane with winds of about 130 mph. The pressure has continued to fall and was last reported at 936 mb just before the Hurricane Hunters left the storm around 1:30 pm. That is the lowest pressure in an Atlantic hurricane since Igor in 2010. A well defined eye is visible on satellite imagery, which is a clear sign that the storm is strong.

Possible Impact Scenarios

Continued strengthening is possible in the next day or so, but there are already clues that an eyewall replacement cycle may be underway (a common process in intense hurricanes where the eyewall contracts and chokes itself off, generally weakening, while a new eyewall forms and eventually takes over – often with strengthening thereafter). As a result, the intensity may level off or fluctuate in the process, but the storm should also enlarge in size. If the cycle completes itself before leaving the Bahamas, additional strengthening afterward is possible through Saturday, when cooler water and higher wind shear should start to weaken Joaquin. The track should continue to loop around the central Bahamas before turning northward by tomorrow. After that it remains very uncertain, as the scenarios below attest. In addition, the impacts to the Northeast and Mid-Atlantic will also be mentioned for each scenario.

Scenario 1: Southeast direct hit (15% chance)

This scenario is much less likely than previously believed, since the trough appears to be coming in later. However, it is still a possibility if the cutoff low can amplify enough to capture Joaquin and send it northwest before it manages to escape. The 06Z HWRF continued to support this possibility, but the 12Z backed away. The 12Z CMC also supports this solution but was poorly initiated. Still, it remains a very viable scenario. Joaquin would likely make landfall late Saturday or early Sunday between Cape Hatteras and the South Santee River on the Carolina coast, with extreme impacts in that region from rain, wind and surge. After landfall, it would likely turn to the north or northwest, possibly after an inland loop in the Carolinas. This would be somewhat similar to Hurricane Fran in 1996.

Northeast impacts: Minimal impact. Most of the moisture is drawn into Joaquin, so the only direct impacts would be heavy rain from the remnants much later.

Mid-Atlantic impacts: Moderate direct impact, especially south of DC. Heavy rainfall would be likely with major flooding possible (greatest flooding would be in the Carolinas). Some wind impact possible in southern areas, and some storm surge flooding also possible.

06Z HWRF run earlier today. Hurricane Joaquin is approaching Atlantic Beach, NC, likely as a Category 3 hurricane.

06Z HWRF run earlier today. Hurricane Joaquin is approaching Atlantic Beach, NC, likely as a Category 3 hurricane.

Scenario 2: Mid-Atlantic direct hit (20% chance)

Despite backing away from the southern solutions, this has seen less model support as well. Nonetheless, the 12Z GFDL model shows a very ominous solution for the Mid-Atlantic, along with some ensemble members. In this case, Joaquin would likely begin to go out to sea, but wouldn’t make it too far. The trough catches up in just enough time to allow Joaquin to make landfall between Cape Henlopen and Cape Hatteras, likely later on Sunday. This would be a devastating scenario for the Mid-Atlantic region with high winds, heavy rain and storm surge all resulting in severe to catastrophic impacts. After landfall, it would likely turn back to the north. While it is definitely less likely than first believed, it is still a reasonable solution. This would be most similar to Hurricane Isabel in 2003 and the 1933 Chesapeake-Potomac Hurricane.

Northeast impacts: Minor to moderate direct impact. Some storm surge flooding is possible along the New Jersey and New York coasts, but not likely to be severe. Some coastal areas may see tropical storm force winds, with some damage possible to trees and some power outages. Main threat is from rainfall both before and during the closest approach of Joaquin.

Mid-Atlantic impacts: Worst case scenario from Philadelphia to Hampton Roads. Significant to extreme storm surge flooding is likely, especially to the north of the landfall point. If it makes landfall just south of Hampton Roads, it would be catastrophic to a low-lying, developed metropolitan area. Major flooding would also be possible in the Chesapeake and tidal Potomac basins, possibly more severe than Isabel, depending on the exact track. A landfall farther north results in those impacts in the Delaware Bay region. Hurricane force winds would be likely in exposed areas with tropical storm force winds elsewhere, resulting in massive power outages and tree damage.

12Z GFDL run today. Hurricane Joaquin is preparing to move onshore late Sunday near the VA-NC border as a Category 2 or 3 hurricane. This would be catastrophic for Hampton Roads and a very bad scenario in the Chesapeake and Potomac basins.

12Z GFDL run today. Hurricane Joaquin is preparing to move onshore late Sunday near the VA-NC border as a Category 2 or 3 hurricane. This would be catastrophic for Hampton Roads and a very bad scenario in the Chesapeake and Potomac basins.

Scenario 3: Jersey Shore/New York City area direct hit (20% chance)

This was the 00Z GFS solution last night, and remains possible based on some ensemble runs. In this scenario, most likely Joaquin would begin to go out to sea. However, similar to Hurricane Sandy in 2012, the trough would eventually capture it very late and send the storm to (or very near) the coast between Montauk Point and Cape May on the Jersey Shore or Long Island, likely on Monday. Given that the trough is not as amplified as it was during Sandy, it is a less likely scenario and may not be enough to send Joaquin inland very far. Regardless, this is a terrible scenario for those areas, especially considering they are still recovering or rebuilding from Sandy.

Northeast impacts: Worst case scenario for the Jersey Shore and/or the New York City region. Significant storm surge is likely to the north and northeast of the landfall point along the Atlantic coast and possibly in Long Island Sound and the New York Harbor. For some areas, it could be more severe than during Sandy or Irene, although not as widespread. The absolute worst case for NYC would be landfall near Long Branch, NJ moving northwest, given the fact that Joaquin should be much smaller than Sandy. Hurricane force winds would be likely in coastal and exposed areas with tropical storm force winds elsewhere, resulting in massive power outages and tree damage. Heavy rainfall will be an additional threat, especially if movement is slow.

Mid-Atlantic impacts: Moderate to significant direct impact, with heavy rain the primary threat and major inland flooding possible. Winds and storm surge would be modest threats, especially to the north with isolated tropical storm force winds possible. Some scattered tree and power line damage is possible.

00Z GFS run last night. In this situation, Hurricane Joaquin is located just south of New York City on Monday afternoon, likely as a Category 1 hurricane.

00Z GFS run last night. In this situation, Hurricane Joaquin is located just south of New York City on Monday afternoon, likely as a Category 1 hurricane.

Scenario 4: New England direct hit (10% chance)

This less likely scenario has little model support (although the official NHC track does show this happening), but several GFS ensemble members do still believe that Joaquin could hit even farther north, or at least come close to the New England coast between Eastport and Watch Hill (including Martha’s Vineyard and Nantucket). Most likely in this case, the trough provides some influence in steering but does not capture Joaquin enough to send it inland farther south. However, the blocking ridge closes off an escape path to the northeast and east, forcing Joaquin to continue northward into New England, likely as a weakening Category 1 hurricane or strong (post-) tropical storm from late Monday to early Wednesday. This has some similarities to Hurricane Edna in 1954 and the 1869 Saxby Gale.

Northeast impacts: Worst case scenario for New England. Significant storm surge is likely to the north and northeast of the landfall point, especially in bays and harbors such as Narragansett Bay, Massachusetts Bay and the tidal Kennebec River which have not experienced major storm surge events in recent decades. Hurricane force winds would be possible in some coastal and exposed areas to the north and east of the storm with tropical storm force winds elsewhere, resulting in significant to massive power outages and tree damage. Inland flooding would also be a threat with significant impacts especially in hilly terrain.

Mid-Atlantic impacts: No direct impacts are likely in the Mid-Atlantic with this scenario. However, heavy rain indirectly associated with Joaquin is likely with additional inland flooding problems.

12Z GFS ensemble run from today for Tuesday afternoon. Notice some ensembles are very close to the New England coast.

12Z GFS ensemble run from today for Tuesday afternoon. Notice some ensembles are very close to the New England coast.

Scenario 5: Out to sea (30% chance)

As mentioned yesterday, the European model has consistently showing Joaquin escaping out to sea, avoiding a significant trough interaction as Joaquin beats out the trough (by either a faster Joaquin or a slower trough) or Ida reforms and an escape route opens. The 12Z GFS, HWRF and UKMET models also fell to that solution, which increases the likelihood of such occurring. Many ensemble runs also followed suit. However, I will only increase the probability slightly at this time, for continuity and the fact that many stragglers (if this is a trend) continue to send Joaquin ashore. In this case, there would be little or no direct impact to the US east coast, although indirect rainfall impacts would still be likely regardless with massive flooding for some. Bermuda and Atlantic Canada would be at serious risk for direct impact, however.

12Z ECMWF run today. Continues to show Hurricane Joaquin well out to sea, but severely impact Bermuda, on Monday morning.

12Z ECMWF run today. Continues to show Hurricane Joaquin well out to sea, but severely impact Bermuda, on Monday morning.

12Z GFS run from today. Hurricane Joaquin is still moving northeast on Monday afternoon, likely towards Atlantic Canada. This is the first run in a long time showing out to sea for the GFS.

12Z GFS run from today. Hurricane Joaquin is still moving northeast on Monday afternoon, likely towards Atlantic Canada. This is the first run in a long time showing out to sea for the GFS.

Scenario 6: Some other solution (5% chance)

Although those scenarios show all of the model runs, there have been times where Joaquin has defied models. Perhaps the trough is too slow and Joaquin is too far south? Or perhaps Ida may redevelop completely? In this case, other possibilities that may appear far-fetched may not be *completely* out of the question, such as land interaction with Cuba dramatically weakening Joaquin or a westerly move beneath the trough into the Caribbean or Gulf of Mexico or into Florida. These could have other impacts to the Northeast or Mid-Atlantic later, but cannot be determined at this time. Still, this is an extremely unlikely set of scenarios.

Conclusion

The models have shown mixed signals, and everything *sounds* better. However, it is extremely important not to let your guards down! This remains a very volatile situation and it involves an extremely dangerous hurricane. One slight change could result in landfall of a powerful and devastating storm. The risk to the Northeast has not really changed at all in that time frame, since yesterday the trend was south. As previously mentioned, VERY heavy rain – on top of the saturated ground that we already have had from this week’s rain – is likely for virtually all of the Northeast and Mid-Atlantic. In some places, the rainfall could be excessive – over a foot easily in total. The greatest totals should be in the southern Appalachians and along the stalled trough axis through the Carolinas, where a week long total of 20 to 30 inches is possible and catastrophic flooding is likely. Other areas could see an additional 4 to 10 inches of rain, with over a foot total for the week including previous events. That assumes Joaquin does not make landfall as well. For the Northeast, the rainfall may be much lower if Joaquin stays out to sea and the ridge holds its influence.

NWS WPC rainfall forecast through next Wednesday. Notice large areas of over 10 inches and a peak of nearly 18 inches, on top of rainfall already fallen (and this is likely conservative).

NWS WPC rainfall forecast through next Wednesday. Notice large areas of over 10 inches and a peak of nearly 18 inches, on top of rainfall already fallen (and this is likely conservative).

There are some signs that look better, but with the mixed signals, it would certainly help to continue preparing. The margin of error is very small, and any change in the forecast could result in a severe hurricane hit before you are ready for it. Any supplies that aren’t used could easily be used in future storms (and we have seen several lately, most notably Irene and Sandy). Not to mention winter storms that are just as dangerous. Joaquin is an extremely dangerous storm and we must continue to respect it. Anywhere from the Carolinas to New England remains at risk at this time. Best to be prepared regardless…and not scared. For those currently being impacted in the Caribbean, my prayers are with you. Stay safe.

Forecaster Craig Ceecee

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