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HURRICANE BLAS DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016
200 AM PDT TUE JUL 05 2016
Blas has continued to strengthen since the previous advisory. The
CDO has improved and the overall convective cloud pattern has
become more symmetrical. A ragged eye feature has been evident in
infrared imagery and is now completely surrounded by cloud tops
colder than -75C. Recent AMSU and ASCAT overpasses have helped
to place the center a little to the northeast of the positions noted
in conventional infrared imagery. The initial intensity has been
increased to 85 kt based on a blend of satellite intensity
estimates of T4.5/77 kt from TAFB and NHC objective intensities
ranging from T4.7-T5.0, and the continued improvement in the eye
pattern depicted in conventional and microwave satellite imagery.
Based primarily on microwave satellite fixes, Blas continues to move
west-northwestward or 285/12 kt. The hurricane is forecast to move
in a general west-northward direction throughout the forecast period
due to a strong deep-layer subtropical ridge remaining nearly
stationary to the north of Blas. The latest NHC global and regional
model guidance remains in excellent agreement on this stable
steering pattern, and the models are tightly packed around the
previous advisory track. Therefore, only minor tweaks were made, and
the new forecast track lies close to the consensus track model TVCE.
Blas has been rapidly strengthening over the past 24 hours, and an
additional 12 hours or so of significant strengthening is supported
by an expanding upper-level outflow pattern, low vertical wind shear
values decreasing to less than 5 kt by 12-24 hours, and a smaller
radius of maximum winds of about 15 nmi noted in recent ASCAT data.
Although vertical shear values are expected to remain low, by 36-48
hours Blas will be moving over SSTs near 26C and ocean heat content
values near zero, which should result in cooling of the ocean
beneath the hurricane and begin a slow weakening trend. By 72 hours
and beyond, Blas will be moving over even cooler water and into a
drier and more stable air mass, negative factors which should
combine to induce more significant weakening. The official intensity
forecast remains well above he consensus model IVCN and closely
follows the GFS-based LGEM statistical-dynamical intensity model,
which has thus far handled Blas' intensification trend the best.
FORECAST POSITIONS AND MAX WINDS
INIT 05/0900Z 14.2N 118.1W 85 KT 100 MPH
12H 05/1800Z 14.5N 119.9W 100 KT 115 MPH
24H 06/0600Z 15.0N 122.2W 110 KT 125 MPH
36H 06/1800Z 15.4N 124.2W 105 KT 120 MPH
48H 07/0600Z 16.0N 126.1W 95 KT 110 MPH
72H 08/0600Z 17.2N 129.8W 80 KT 90 MPH
96H 09/0600Z 19.1N 133.0W 60 KT 70 MPH
120H 10/0600Z 20.7N 136.4W 40 KT 45 MPH...POST-TROPICAL
$$
Forecaster Stewart
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