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TROPICAL STORM AGATHA DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP022016
200 AM PDT MON JUL 04 2016
The amount and organization of deep convection in Agatha continues
to decrease overnight due to the combination of moderate
southwesterly vertical wind shear and a cool, stable airmass.
Correspondingly, the 06Z Dvorak numbers from SAB and TAFB have
dropped and would typically suggest that the system has weakened to
a tropical depression. However, ASCAT scatterometer passes at 0510Z
and 0602Z indicate that the strongest winds were near 40 kt at those
times. Given the continued deterioration of the convection since
then, the initial intensity is analyzed to be 35 kt.
It is not likely that Agatha will experience any additional
intensification episodes. The adverse effects of increasing
southwesterly vertical shear, cool 24C waters, and more stable air
should lead to Agatha dropping to a tropical depression later today
and becoming a remnant low by Tuesday. The NHC intensity forecast -
nearly unchanged from the previous advisory - is based on a blend
of the LGEM/SHIPS statistical schemes and the GFDL mesoscale model.
Agatha is moving at 280 degrees/11 kt, primarily steered by a
deep-layer ridge to its northeast. Uncertainty in the current
location and movement is low, due to the scatterometer passes, as
well as an earlier GMI microwave image. As Agatha weakens and
becomes a shallow remnant low steered by the low-level flow, the
system should turn slightly toward the west or west-southwest at a
slower forward speed. The global and mesoscale hurricane model
guidance is in a tightly-clustered agreement with this scenario, and
the NHC track forecast is very similar to the previous advisory.
FORECAST POSITIONS AND MAX WINDS
INIT 04/0900Z 18.1N 127.1W 35 KT 40 MPH
12H 04/1800Z 18.4N 128.7W 30 KT 35 MPH
24H 05/0600Z 18.8N 130.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 05/1800Z 18.9N 132.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 06/0600Z 18.7N 134.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 07/0600Z...DISSIPATED
$$
Forecaster Landsea
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