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Tropical Storm Alvin Discussion Number 4
NWS National Hurricane Center Miami FL EP012019
900 AM MDT Wed Jun 26 2019
Visible and passive microwave imagery this morning indicate that the
center of the tropical cyclone is located farther south than
previously estimated, possibly due to a reformation of the center.
The center of the cyclone is now embedded near the deepest inner-
core convection, and some overall improvement in the convective
pattern is evident. Satellite intensity estimates indicate that
the cyclone has reached tropical storm strength, and the initial
intensity of 35 kt is based on the latest Dvorak estimate from SAB.
Alvin's formation marks the 3rd latest date of the development of
the first named storm in the eastern Pacific basin during the
satellite era (since 1966).
Alvin has turned a little south of due west and the initial motion
estimate is 260/12 kt. The new NHC forecast track over the first
couple of days has been adjusted southward, in large part due to the
more southerly reformation of the center. Despite this, the overall
track forecast philosophy has not changed. Alvin is expected to move
westward and then west-northwestward with a gradual decrease in
forward speed over the next few days along the southwestern
periphery of a subtropical ridge.
There remains about a 24-36 hour window for some additional
strengthening to occur over warm SSTs in a low-shear and
sufficiently moist environment. This environment, combined with the
improving structure of the storm, supports raising the intensity
forecast a little in the near term. The new NHC forecast is in good
agreement with the dynamical models and the intensity consensus.
After 36 hours, the forecast track takes Alvin over progressively
cooler waters and into a drier and higher-shear environment. This
should result in steady weakening, with the cyclone likely becoming
devoid of deep convection by 72 hours, and dissipating by day 5.
FORECAST POSITIONS AND MAX WINDS
INIT 26/1500Z 14.7N 109.4W 35 KT 40 MPH
12H 27/0000Z 14.7N 111.4W 45 KT 50 MPH
24H 27/1200Z 15.0N 113.7W 45 KT 50 MPH
36H 28/0000Z 15.7N 115.8W 45 KT 50 MPH
48H 28/1200Z 16.4N 117.7W 40 KT 45 MPH
72H 29/1200Z 17.4N 121.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 30/1200Z 18.0N 124.0W 20 KT 25 MPH...POST-TROP/REMNT LOW