Atlantic/2019/10L/Archive/5

At least for now, Jerry has proven the global synoptic guidance wrong when it comes to intensity. The feisty tropical storm has maintained the stout conventional curved band appearance that emerged last advisory, featuring a central hub of -70C cloud tops and an arc of active convection extending in the western semicircle out to the north and east. At times, convection has dropped below -90C which is unusual for the central Atlantic. The low-level center has come into better alignment with the curved band based on microwave data from 1700z and 1914z, and is now nestled squarely under the central convective mass. The latter of these passes suggested that Jerry was beginning to take on a central dense overcast as opposed to a curved band structure. SAB and TAFB gave T3.5/55kt estimates at 18z while UW-CIMSS ADT was more bullish at T3.9/63kt. Based on this and the totality of microwave structure and pressure estimates, the current intensity has been raised to 55kt.
It is hard to know with high confidence whether Jerry is currently in a rapid intensification regime, though I haven't seen any setbacks in the storm's organization over the course of the afternoon and early evening. As hypothesized yesterday, Jerry has taken advantage of a local decrease in deep-layer wind shear to below 5kt. This golden hour may not last very long, however, as an upper-level low looms just northeast of the Virgin Islands. An increase in deep-layer northerly wind shear to 15-25 kt is forecast over at least the next two days from this feature. Given the rather dry mid-level conditions of the region, Jerry's intensity over the next few days will depend on whether or not it can avoid significant entrainment while traversing the central Atlantic. After two days, Jerry will be in a highly location-sensitive position relative to an upper-level anticyclone over the eastern Caribbean, and small changes in track could mean either persistent 20 kt wind shear or a decrease to a much more manageable 10-20kt between days 3-4, before shear increases at day 5. Thermodynamic fields become highly favorable after day 2, so it will be mostly the kinematic parameters that will need monitoring. For now, Jerry's quicker intensification is expected to level off towards gradual intensification behavior out to day 4 in response to shear before late-term weakening due to an increase in east-northeasterly flow from the weakness carved out by Humberto.
The broader track setup for Jerry is "simple" but is complicated in the finer detailing by the storm's future intensity, which remains uncertain. The plurality of track guidance largely follows the same idea: a general track towards the west-northwest for about three days around the southwestern periphery of the subtropical ridge before Humberto begins to curve northward into the weakness evacuated by Humberto. However, since upper-level ridging is expected to strengthen over the Southeastern United States in roughly three days, there is a bifurcation emergent in some of the ensemble guidance where a stronger storm would be drawn farther south, which has impact implications for the Leeward Islands and Greater Antilles. At present, given short-term biases from the guidance so far towards the north and east, the current forecast track is west of most guidance but still north of the islands, with a curve towards the northwest late in the window. However, impacts, and even a landfall, cannot be ruled out in the eastern Caribbean.

FORECAST MAX WINDS
INIT 18/2100Z 55 KT 65 MPH
12H 19/0600Z 60 KT 70 MPH
24H 19/1800Z 65 KT 75 MPH
36H 20/0600Z 65 KT 75 MPH
48H 21/1800Z 70 KT 80 MPH
72H 22/1200Z 70 KT 80 MPH
96H 23/1200Z 65 KT 75 MPH