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Tropical Storm CRISTOBAL (Text)

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TROPICAL STORM CRISTOBAL DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042014
500 PM EDT SUN AUG 24 2014

Cristobal's convective cloud pattern has not changed much during the
past 6 hours, other than cloud tops having warmed some. Aircraft and
satellite data indicate that the inner-core wind field is still
broad, with multiple small swirls rotating around a mean center. Air
Force Reserve and NOAA reconnaissance aircraft data indicate the
central pressure has remained steady at 1001 mb, so the initial
intensity will be kept at 40 kt for this advisory.

The initial motion is northward or 360/7 kt. The NHC model guidance
has come into much better agreement on this cycle with the GFS track
having shifted westward and the ECMWF model having shifted eastward.
The rest of the models are reasonably close to the GFS and ECMWF
solutions. There is one main difference, however, which is the track
speed, with the GFS model lagging behind the ECMWF model and some
of the other models by more than 500 n mi at 120 hours. Cristobal
is expected to continue moving northward through a weakness in the
subtropical ridge and slow down over the next 72 hours as a strong
upper-level trough east of North Carolina lifts out to the
northeast. A second trough currently over the upper Midwest is
forecast to dig southeastward along the U.S. east coast by Days 4
and 5 and accelerate the cyclone northeastward over the north
Atlantic. The official forecast track has been shifted eastward
through 72 hours, and then shows a faster forward speed similar to
the ICON consensus model at 96 and 120 hours.

Light to moderate northwesterly to northerly shear is forecast to
affect Cristobal through 72 hours, which should allow for only slow
strengthening to occur. When Cristobal makes a northeastward turn
and accelerates after that time, the shear is expected to decrease
while the cyclone is over near-29C SST, which should allow Cristobal
to strengthen into a hurricane. The NHC intensity forecast is
similar to the previous advisory, and closely follows the consensus
intensity model ICON.

FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 24.5N  73.0W   40 KT  45 MPH
 12H  25/0600Z 24.9N  73.1W   45 KT  50 MPH
 24H  25/1800Z 25.7N  73.0W   50 KT  60 MPH
 36H  26/0600Z 26.6N  72.8W   55 KT  65 MPH
 48H  26/1800Z 28.4N  72.5W   60 KT  70 MPH
 72H  27/1800Z 31.9N  71.8W   65 KT  75 MPH
 96H  28/1800Z 35.0N  66.5W   70 KT  80 MPH
120H  29/1800Z 39.5N  58.0W   70 KT  80 MPH

$$
Forecaster Stewart

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