csnavywx

Definitely seeing a bit of rotation of convection upshear. Still too early for a full recoupling, but the air coming in is a little less dry and shear should gradually improve tonight before more rapid improvement tomorrow during the day (and coupling begins with the upper jet). The shear is still strong enough to decouple the convection if it weakens though, so it's still at risk of losing it and bursting again later.

The ol' diffluent southwesterly shear pattern ahead of that trough further north still has room to surprise a bit. At the very least, I would expect to see an expansion of banding and the rain shield in general when it starts getting further north. Until then, bursts and shear-offs rule.

Probably not. There is still southwesterly shear and enough dry air to keep convection from closing off reliably. The near-complete lack of outer banding is also a detriment as that typically helps slow down mitigate intrusions into the core. As it interacts with the jet to the north, the precip shield may expand, but that may not be enough to give it the boost it needs to pull that kind of scenario.

A little bit more in-depth look at a similar scenario in TS Edouard ('02): https://journals.ametsoc.org/mwr/article/141/3/1048/71507/Convective-Bursts-Downdraft-Cooling-and-Boundary Isaias may follow a similar pattern over the next day or two. Basically, dry air and shear destroy convection through cool downdrafts, stabilizing the atmosphere and cutting off further convection. However, the boundary layer in the resulting open swirl begins to recover and eventually fires off a new convective burst. This pattern can continue for some time until conditions worsen further or allow redevelopment. Whether or not Isaias makes landfall or stays just offshore may depend on the timing and frequency of such bursts. On Monday, shear conditions begin to improve and a combination of that and divergence aloft from the entrance region of the jet and a more south-southwesterly steering vector may allow for a short period of strengthening -- provided the LLC hasn't been distorted or weakened enough to preclude that.

This wasn't completely unexpected. HWRF and others showed a pretty typical sheared burst-type pattern for the storm as it approached FL and before it turns north. Convective bursts followed by LLC exposure and a sawtooth weakening pattern. Shear should lessen a bit should it manage to stay over water after it turns north.

Little bit of land interaction there is doing it in. That plus the dry air and shear is a bit too much.

The shear only gets worse from here to FL. It's very possible this thing simply gets decapitated on approach and ends up inland over FL as a naked swirl. Right now, there's 15-20 knots of westerly/southwesterly shear. By the time we get close to FL, it's more like 25-30 on most of these model runs. It can't really afford to lose ground between now and then.

Also a wind shift at MDPP and a surface pressure fall of 6mb in about 2.5 hours: MDPP 301920Z 03025G35KT 3000 +RA OVC016 26/25 Q1003 MDPP 301900Z 05026KT 7000 -RA BKN018 BKN300 26/25 Q1005 MDPP 301800Z 08025KT 9999 BKN018 BKN300 27/26 Q1008 MDPP 301700Z 08024KT 7000 -RA BKN018 BKN070 27/26 Q1009

MDST or Cibao International in the northern part of DR has flipped from calm or light southeasterly, to west-northwest in the past 2 hours, with a drop of 3mb (down to 1005). The airport is located at 565ft elevation, strongly suggesting that there is a new LLC nearby: MDST 301900Z 28016KT 9999 FEW014CB BKN015 OVC070 25/25 Q1005 CB/NE/E/S/SW/N MDST 301800Z 30008KT 2000 +RA FEW014CB BKN015 OVC070 25/25 Q1007 CB/NE/E/SW/N MDST 301700Z 00000KT 7000 -RA FEW016CB BKN017 BKN070 26/25 Q1008 CB/NE/E/S/SW/N MDST 301600Z 11004KT 7000 -RA FEW015CB BKN016 OVC070 25/25 Q1009 CB/NE/E/S/SW/N MDST 301500Z 14006KT 9999 FEW014CB BKN015 0VC070 26/25 Q1010 CB/NE/E/SW/N MDST 301400Z 00000KT 6000 -RA FEW015CB BKN016 24/24 Q1010 CBE/SW/N

If that has indeed occured, this storm has a chance to intensify. There's a pretty bimodal set of outcomes: one in which the vortex quickly spins up and puts out enough outflow to resist the PV streamer's influence to the west and one in which it doesn't and instead lives most of its life fighting that off until it starts to recurve.

Definitely evidence of LLC reformation on latest vis sat and observations are starting to support that. Notice the new VHTs just east of the new apparent center and convection that has rotated upshear. Old LLC appears to be quickly getting destroyed by land interaction.

Convection still dominant in the southern/western portion of the wave. While the northern end will still need to be watched and genesis is typically favored there in most waves (curvature typically best there), that's not *always* going to be the area of initial formation and this could end up being one of those exceptions.

Big convective burst ongoing tonight. Won't take long for the circulation to start strengthening and tightening up if this keeps up.

Amazing how it's only mid-July and there's virtually nothing left in the Laptev and only scraps in the ESS. The open water front is now in the CAB in record time and with some quality insolation time left on the clock. EPS/GEFS suggest this nuclear blocking pattern is finally backing off, but there are hints that it may be a temporary reprieve if the idea of a more NA centered blocking event past D5/D6 is correct. If that sets up into another event, this year will likely kill off 2012's record. Threre isn't enough peripheral ice left to keep the CAB from taking the brunt, except on the Beaufort side (which is actually doing better than any time since 2013). Having said that, we should see some slowdown in extent losses after D2/D3 for a while. The pack is already pretty compressed, so some dispersion is probably inevitable with the incoming lows. I'm thinking there's a legit chance of clear open water at the pole this year. We've had a couple of years where it came close, but nothing with the start on the Eurasian side like this year has had.

Big dipole to start the month, relaxed a few days later and then a monster Greenland ridge centered around the 12th. That pattern relaxed into a strong +PV for a while with a weaker dipole event to end the month. GAC strikes at the end of the first week of August and by that point is able to sweep away most of the low-extent ice. Overall the first half is dominated by storminess, with a return to Greenland ridging and a dipole-like pattern to finish the month. Most of the damage is done with the early June and early July dipole events (with the mid-July Greenland ridge pattern no doubt helping export).