Atlantic/2019/05L/Archive/12

Dorian moved across Saint Lucia this morning, and its tiny circulation was severely disrupted. The reconnaissance plane this morning had difficulty closing off a well-defined circulation for a time. However, later investigation through the use of radar imagery found that a new surface low developed west and north of Martinique. That same radar imagery shows that the circulation has become markedly better defined in recent hours, accompanied by an increase in spiral banding features near the center. Satellite intensity estimates, coupled with earlier observation data from the Air Force reconnaissance plane, support maintaining the initial intensity at 45kt.
Dorian's long-term motion appears to be toward the northwest this evening, although recent radar frames have been deviating more toward the north-northwest. The cyclone is situated on the western side of a mid-level ridge north and east of the Leeward Islands. That ridge, plus a mid-level trough near the Turks and Caicos Islands, should force Dorian on a northwest trajectory for the next few days. The biggest change this afternoon has been the center reformation toward the north, which ultimately results in a track shift to the right. While earlier predictions called for a close pass with the island of Hispaniola, this seems dramatically less likely now. Instead, Dorian is expected to make landfall in Puerto Rico in a little over 24 hours and continue into the southwestern Atlantic. After day 3, an expansive ridge is expected to develop off the Southeast United States, forcing the system on a west-northwest and eventually westward track. While not explicitly stated at this time, the combination of the strong ridge to Dorian's north and a mid-level trough over the Gulf of Mexico may induce a west-southwest motion as the system approaches Florida about 5 days from now.
Dorian continues to contend with mid-level dry air entrainment this afternoon, though convection has been generally persistent in spite of that fact. Moving forward, mid-level relative humidity values are forecast to steadily climb as Dorian moves toward the southwestern Atlantic, and ocean temperatures will remain more than sufficient around 28-29C. A slight uptick in wind shear is still expected tomorrow, with values between 10-15kt expected for approximately 18 hours according to the SHIPS text output. After that time, upper-level winds are expected to become conducive once again. Given the small size of Dorian, this increase in shear should be sufficient enough to limit intensification, and as the system crosses Puerto Rico, some weakening may occur. Thereafter, though, the environment should become quite conducive. All model guidance is in agreement that the 200mb wind pattern will become exceptionally favorable, with multiple ventilation outlets at Dorian's disposal, and the prospects for a rapidly-intensifying cyclone are increasing. The new forecast is largely an update of the last one, except to raise the intensity in the later period of the forecast and to depict a Florida landfall.
FORECAST MAX WINDS
INIT 27/2100Z 45 KT 50 MPH
12H 28/0600Z 45 KT 50 MPH
24H 28/1800Z 45 KT 50 MPH...APPROACHING PUERTO RICO
36H 29/0600Z 40 KT 45 MPH
48H 29/1800Z 45 KT 50 MPH
72H 30/1800Z 50 KT 60 MPH
96H 31/1800Z 60 KT 70 MPH