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| #1154836 (Received by flhurricane at: 10:41 PM 27.Sep.2023) TCDAT2 Tropical Storm Philippe Discussion Number 19 NWS National Hurricane Center Miami FL AL172023 1100 PM AST Wed Sep 27 2023 Deep convection has persisted around the eastern portion of Philippe`s circulation this evening, however there is not much evidence of curved bands. The low-level center may have reformed or become slightly better defined just to the west of the main convective mass since the previous advisory. There has been no recent microwave imagery to gain a better look at the cyclone`s structure and scatterometer appears likely to miss the center this evening. The latest subjective Dvorak intensity estimates were T3.0 (45 kt) and T2.5 (35 kt) from TAFB and SAB, respectively. The initial intensity is held at 45 kt for this advisory, in deference to the earlier scatterometer data and latest TAFB estimate. The track forecast for Philippe remains quite complicated, and it is very dependent on the future intensity and vertical depth of the cyclone. The current disorganized structure of Philippe and its present environment of moderate southwesterly shear is likely to inhibit strengthening over the next couple of days. The main question is whether Philippe weakens and becomes more vertically shallow or if it maintains some vertical coherence during that time. If it becomes vertically shallow, Philippe is likely to move generally westward or west-southwestward within the low-level steering flow. If it remains more vertically deep, the cyclone is likely to move little as it remains to the southeast of a mid-level ridge. Another complicating factor is a disturbance (AL91) to Philippe`s southeast. The latest GFS run moves that system close enough to Philippe that binary interaction occurs between the two systems. However this run appears to have initialized Philippe stronger than it actually is, which may have led to the solution where Philippe remains the dominate system. Meanwhile, the ECMWF weakens Philippe and keeps more separation between the two systems, taking a weaker Philippe westward or west-southwestward. The NHC forecast currently favors the latter scenario, but there is an unusually large amount of uncertainty in the track and intensity forecast. In general, the guidance is a bit slower this cycle and the NHC forecast has been adjusted accordingly. The new track forecast is not as slow as the consensus aids, but is a blend of the previous official forecast and the latest consensus models. It would not be surprising if additional adjustments to the track forecast are required in subsequent advisories. As mentioned above, moderate southwesterly shear and a slightly drier airmass ahead of Philippe are likely to inhibit significant convective organization of the cyclone at least during the next day or two. That is likely to cause some gradual weakening, and the NHC intensity forecast follows that thinking and calls for the system to weaken during that time. However, there is still a lot of uncertainty as to whether Philippe weakens and becomes a remnant low later in the period, or moves little and remains a tropical cyclone. The latest forecast maintains continuity from the previous few advisories and calls for Philippe to become a remnant low, but this is a low confidence forecast. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 18.2N 54.5W 45 KT 50 MPH 12H 28/1200Z 18.7N 55.5W 45 KT 50 MPH 24H 29/0000Z 19.0N 56.6W 40 KT 45 MPH 36H 29/1200Z 19.0N 57.6W 40 KT 45 MPH 48H 30/0000Z 19.0N 58.6W 40 KT 45 MPH 60H 30/1200Z 18.7N 59.4W 35 KT 40 MPH 72H 01/0000Z 18.5N 60.3W 35 KT 40 MPH 96H 02/0000Z 18.5N 62.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 03/0000Z 18.5N 63.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown |
