Tropical Storm Dorian has made a bend more toward the west this evening, and based on satellite loop imagery, is moving just north of due west. Smoothing out the track from fluctuations, yields a current motion of 290 degrees. Dorian is located on the southern periphery of a fairly strong sub-tropical ridge. As of the 5:00 p.m. EDT advisory from the NHC, the following information was provided on Dorian:
5:00 PM AST Thu Jul 25
Location: 16.5°N 37.8°W
Moving: WNW at 18 mph
Min pressure: 999 mb / 29.50 in
Max sustained: 60 mph
Based on current and forecast steering maps, I expect the westward motion to continue overnight, with more of a WNW (295-300 deg.) motion resuming possibly tomorrow. Dorian’s track will fluctuate between this medium, as the ridge continues to to show subtle changes in its orientation. I expect this motion to continue for the next 4-5 days, based on the current run of the forecast layers steering maps from the PSU e-WALL site, and 18Z run of the Dynamic Model Guidance suite. This motion will continue, as there is a notable weakness in the ridge which is located just north of Hispaniola at the moment. The forecast steering layers maps suggest this ridge will continue to nose toward the west, along with Dorian, providing that WNW motion. After or around day 5 in the forecast period, steering may be a little tricky, and will depend on the timing and strength of Dorian.
If Dorian survives the trek into the southern Bahamas area, there appears to be enough of a weakness in the ridge at that moment, to bring the system close to FL to around SC. However, based on motion from the forecast steering maps, and recent analysis of the GFS and CMC model solutions, both models weaken Dorian into an open wave, with the GFS bring him WSW over Puerto Rico, then into the Caribbean…and the CMC just north of the Cuban coast. The latter solution cannot be ruled out, and may be plausible, as by day 5, or around 120 hours Dorian will be under some fairly robust SW wind shear, regardless if he remains north of the Island of Cuba, or enters the Caribbean.
Dorian has maintained his strength of 60 mph, and there has really been little change in the storm structurally over the past 4-6 hours, albeit the last few loops of satellite imagery indicate the LLC is staying much closer under the convective activity.
Convection has waned somewhat, with some warming of the cloud tops, and this may be a hiccup, as Dorian has ingested some dry air in the southern periphery, with a small outflow boundary that was noted to the north of the storm about 1-2 hours ago.
The current wind shear map from CIMSS still indicates a small upper level anticyclone over Dorian at the moment, and the GFS Zonal Shear forecast is still persistent in showing upper level winds conducive for development during the next 96-120 hours. Given the uncertainty of how much dry the storm may ingest, I have to agree with the NHC intensity forecast up to day 5, albeit I still will not rule out the probability of Dorian attaining Category 1 Hurricane status before it’s all said and done, as two factors will be in his favor…warmer sst’s, and favorable upper level conditions.
I will continue to monitor the progress of Dorian for any significant changes, and will have another update in the a.m.
Have a blessed evening.
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)