Big changes – and things to remember

Good evening.

I know I posted my thoughts on this week’s forecast only a few hours ago, but there are major changes from the 12Z model suite. However, I first need to make a few points:

  1. 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.
  2. While I am quite confident this system is not going out to sea (at least not initially) due to a strong blocking ridge, it doesn’t appear that the backing trough that the ECMWF model shown below will occur. No other model suggests it.
  3. Mesoscale models (the GFDL and HWRF) are very unreliable with initially weak storms, and practically useless in extratropical transition and trough interaction situations.
  4. 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 through midweek, with 3 to 6 inches of rain in spots. That is a virtually certain scenario and more worthy of our immediate concerns.
  5. Even if this was sure to be coming our way, it is still at least 4 to 5 days away. 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.
What The Models Say

Anyway, several models decided to shock us all and boost the general hype meter in the weather community and on social media. First, the 12Z HWRF (run just after I posted the previous update) showed the system becoming an intense Category 4 hurricane with a pressure near 927 mb offshore of the Carolinas, and making landfall as a Category 3 storm in central New Jersey early Saturday morning, remaining a hurricane across the New York metropolitan area into central and northern New York. That is an EXTREMELY unlikely scenario due to the wind shear expected (especially close to the coast near and west of 75W longitude), plus it doesn’t take into account the extratropical transition or stationary front at all.

Virtually impossible scenario from the HWRF showing Hurricane Joaquin making landfall near Atlantic City on Saturday morning as a Category 2 or 3 storm. The conditions do not support such.

Virtually impossible scenario from the HWRF showing Hurricane Joaquin making landfall near Atlantic City on Saturday morning as a Category 2 or 3 storm. The conditions do not support such.

Not to be outdone, the reliable ECMWF model also showed a scenario reminiscent of Hurricane Sandy, with a strong upper-level low cutting off in the southeastern US and the storm (at the time a Category 1 storm) pinwheeling northwest with the trough into the coast near Hampton Roads or the southern Delmarva, only to do a loop over land then ride back up the east coast. Again, this is not a likely scenario.

The reasons are numerous: first, unlike Sandy, this is happening a month earlier in the season, when troughs don’t dig as far south with as much intensity. Not until November do strong troughs begin to reach Florida under normal circumstances. Second, in order to develop such a strong upper-level low, it required the remnants of 99L to deepen over land and essentially merge with TD 11 (then Joaquin most likely). That doesn’t appear likely. In addition, that would require the trough to build back then go into a negative tilt and the ridge would need to build southward and westward. Most models show it holding near Newfoundland over the time frame.

12Z ECMWF model run showing Hurricane Joaquin phasing with a trough and making landfall near Hampton Roads, similar to Sandy but with a weaker storm. Also not a likely scenario.

12Z ECMWF model run showing Hurricane Joaquin phasing with a trough and making landfall near Hampton Roads, similar to Sandy but with a weaker storm. Also not a likely scenario.

So what will happen?

There are numerous reasonable possibilities. The ensembles are all over the map, showing possibilities from early dissipation to a strong hurricane offshore looping to landfall somewhere between North Carolina and New England. A fairly straight track to the New England or upper Mid-Atlantic coast, like the NHC forecast, is most likely in my opinion, but it is still VERY early. Stay tuned.

However, the biggest threat – regardless – is rainfall.¬†First, the frontal boundary and moisture from 99L should lead to significant rainfall in most of the Northeast. 3 to 6 inches is quite possible along the I-95 corridor, with lesser amounts in the coastal plain south of NYC and in northwestern areas near Lake Ontario and the St. Lawrence River valley. And that is only through Thursday…it doesn’t even capture any rainfall potential from TD 11.

WPC precipitation forecast through Thursday. In my opinion, these amounts are probably conservative.

WPC precipitation forecast through Thursday. In my opinion, these amounts are probably conservative.

Fortunately, as previously mentioned, the Northeast is abnormally dry, so this first round of rainfall is much needed. However, it remains to be seen what could happen later with the ground becoming more saturated. That we won’t know for at least a couple days, but some models show large areas receiving 6 to 12 inches of rain this week, with locally up to 20 inches in some spots. It is way too early to consider this forecast accurate, however, since there is a wide range of possibilities.

GFS precipitation forecast through Sunday morning. Notice large areas of 4 to 8 inches of rain, with spots in eastern New England as high as 20 inches!

GFS precipitation forecast through Sunday morning. Notice large areas of 4 to 8 inches of rain, with spots in eastern New England as high as 20 inches!

This is definitely an event that needs to be watched, but it is certainly not panic time by any means. Don’t jump to conclusions based on one model run. Consistency is key and the ensembles are not in agreement at all at this time.

Forecaster Craig Ceecee

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