Atlantic/2019/02L/Archive/4

Tropical Storm Barry remains fairly disorganized this afternoon. Convection is exclusively focused across the southern semicircle of the storm thanks to the influence of continental dry air and moderate northerly wind shear. Meanwhile, visible imagery and recon data indicates that the low-level circulation remains broad, with several mesovortices embedded within this larger gyre. For that reason, getting a good grip on the position of Barry's "center" has been difficult this afternoon. Broad pressures are in the neighborhood of 1003-1004mb, but an earlier mesovortex yielded sub-1000mb pressures as the reconnaissance aircraft was departing Barry a while ago. Assuming this was indeed transient, the minimum pressure has been set to 1003mb, which depicts a slow deepening of the cyclone since this morning. The initial intensity remains 35kt on the basis of numerous tropical storm-force wind measurements in the southeast quadrant.
The broad circulation of Barry has tracked south of west during the day today. However, a weak shortwave trough is pushing across Illinois and Missouri right now, helping to erode a broad mid-level ridge across Colorado and New Mexico which was the impetus for an equatorward motion the past 36 hours. In the wake of this trough, the ridge will push eastward and attempt to rebuild, though at a much weaker state than it found itself yesterday. At the same time, a potent mid-level ridge off the Southeast United States will nudge westward. The influence of the first ridge argues for a westward motion, while the influence of the stronger, second ridge argues for a northward trajectory. The end result is that Barry should move west-northwest to northwest up until landfall. In addition to the evolution of these highs, where Barry's center ultimately consolidates will have a say in where landfall is. While earlier models had shifted east into eastern Louisiana, the trend in the 12z guidance was to return westward, including the GFS ensembles which notably jumped almost to the Texas-Louisiana border. For now, the landfall point has been nudged back westward toward Marsh Island early Saturday morning.
The intensity forecast for Barry is complicated both from an environmental standpoint as well as a track standpoint. Though models such as the ECMWF and UKMET nailed tropical cyclogenesis potential, both models showed a more vertically stacked storm than we are contending with today; the point goes to the GFS in that regard. The dislocation in low- to mid-level centers is the result of about 15kt of northerly wind shear, helping to inject dry air from the East United States into the northern semicircle of Barry. In order for the storm to substantially intensify, the low-level center will need to condense. This process is likely to occur as one of the many mesovortices in the larger gyre swings south into the deep convection, allowing continuous pressure falls there. Once this occurs, persistent thunderstorm activity should release enough latent heat to reduce upper-level winds near Barry, although this will not completely negate the shear. Ocean temperatures are more than suitable for a tropical cyclone of any strength, with values generally near 30C through landfall. Given an environment that is likely to allow a general upward trend in intensity, the biggest question for the purpose of this advisory is how long Barry has over water to take advantage of the adequate conditions. A storm that moves inland tomorrow night would likely only have time to become a strong tropical storm or perhaps a minimal hurricane. A storm that moves farther west and makes landfall Saturday mid-morning could become a stronger Category 1 hurricane. Accounting for all the discussion above, I have slightly reduced the forecast to a peak strength of 70kt at landfall. This continues to be a low confidence forecast. Barry may only slowly weaken over the marshes of Louisiana initially, with more rapid weakening once it continued northward. Degeneration is expected in 4 days.
FORECAST MAX WINDS
INIT 11/2100Z 35 KT 40 MPH
12H 12/0600Z 40 KT 45 MPH
24H 12/1800Z 50 KT 60 MPH
36H 13/0600Z 65 KT 75 MPH
[N/A 13/1200Z 70 KT 80 MPH...LANDFALL]
48H 13/1800Z 55 KT 65 MPH...INLAND
72H 14/1800Z 30 KT 35 MPH...INLAND
96H 15/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW