000
WTNT41 KNHC 090851
TCDAT1

TROPICAL STORM ANA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012015
500 AM EDT SAT MAY 09 2015

Satellite and NOAA Doppler radar data indicate that Ana has likely
made the transition to a tropical cyclone based on the rapid decay
of a previously persistent band of outer convection, recent
development of inner-core convection within 30-40 nmi of the
center, and weak anticyclonic outflow. Between 0500-0700 UTC,
average Doppler velocities of 58-60 kt with isolated peak values of
63 kt were noted between 8,000-10,000 ft and within 30-40 dBZ
echoes, which would correspond to about 53-54 kt surface winds.
However, since that time, that outer band has weakened considerably,
so the initial intensity will remain at 50 kt for this advisory.

The initial motion estimate using a 12-hour motion is 340/03 kt.
There is no significant change to the previous forecast track or
reasoning. The global and regional models are in very good
agreement that Tropical Storm Ana will move slowly toward the
north-northwest or northwest for the next 36 hours or so, followed
by a gradual turn toward the north and northeast ahead of an
approaching deep-layer trough. By 72 hours, Ana is expected to
become extratropical and be absorbed by a much larger extratropical
low pressure system by 96 hours. The official track forecast is
similar to the previous advisory and lies close to the multi-model
consensus TVCN.

The center and inner-core region of Ana currently lie along the
axis of warmest Gulf Stream water of about 25C. Although inner-core
convection has been developing during the past few hours, it is
occurring in a region where the last recon flight only found winds
of 30-40 kt at the surface and around 45 kt at flight-level. As a
result, there could be some fluctuations in Ana's intensity in the
near term this morning. By 12-24 hours, the cyclone's slow forward
speed will take it over much cooler shelf waters. The combination of
SSTs around 20C-22C and continued entrainment of mid-level dry air
should induce at least slow weakening until landfall occurs.
Although inland at 36 and 48 hours, the intensity has been held up
slightly in anticipation of a band of stronger winds lying just
offshore. The official intensity forecast is similar to the
intensity consensus model ICON.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 32.4N  77.6W   50 KT  60 MPH
 12H  09/1800Z 32.8N  77.9W   45 KT  50 MPH
 24H  10/0600Z 33.5N  78.4W   40 KT  45 MPH
 36H  10/1800Z 34.3N  78.6W   35 KT  40 MPH...INLAND
 48H  11/0600Z 35.2N  78.0W   30 KT  35 MPH...INLAND
 72H  12/0600Z 39.0N  73.9W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z...ABSORBED BY LARGER EXTRATROPICAL LOW

$$
Forecaster Stewart