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WTPZ42 KNHC 231433
TCDEP2

Tropical Storm Greg Discussion Number 25
NWS National Hurricane Center Miami FL EP072017
800 AM PDT Sun Jul 23 2017

Greg's convective pattern is looking a little better this morning, with two distinct bursts of thunderstorm activity located near and to the west of the center. The latest Dvorak intensity estimates range from T2.0 to T3.0, and the initial intensity will remain 45 kt since the cyclone's structure has improved somewhat during the past several hours.

Vertical shear over Greg is less than 10 kt at the moment, but the cyclone's biggest challenge is dry air in the surrounding environment. GOES-16 lower-level water vapor imagery shows that Greg is running into a very dry low- to mid-level air mass to its west, and this environment will likely curtail strengthening. Greg is forecast to maintain its intensity for another 24 hours, followed by gradual weakening due to the dry air, increasing shear, and cooler sea surface temperatures after 48 hours. This scenario is captured by all of the intensity guidance, and Greg is likely to degenerate into a remnant low by 96 hours.

A little more southward adjustment of the center location was needed based on additional ASCAT and other microwave data received since the last advisory. Still, low- to mid-level ridging to the north of Greg is expected to maintain a westward motion through 36 hours. The ridge is forecast to weaken after 36 hours, which should allow the cyclone to gain a little more latitude on days 2 through 4. The low-level trade winds are then expected to push the remnant low west-southwestward by day 5. Except for a southward adjustment in the track forecast to account for the initial position, the model guidance is in good agreement, and no other significant changes were required from the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 14.3N 129.0W 45 KT 50 MPH 12H 24/0000Z 14.3N 130.7W 45 KT 50 MPH 24H 24/1200Z 14.5N 133.0W 45 KT 50 MPH 36H 25/0000Z 14.7N 134.8W 40 KT 45 MPH 48H 25/1200Z 15.0N 136.2W 35 KT 40 MPH 72H 26/1200Z 16.1N 138.6W 30 KT 35 MPH 96H 27/1200Z 16.5N 141.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 28/1200Z 15.9N 143.6W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$ Forecaster Berg

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