000WTNT42 KNHC 051445TCDAT2TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 1NWS NATIONAL HURRICANE CENTER MIAMI FL AL0720151100 AM AST SAT SEP 05 2015Satellite imagery and ship observations indicate that thedisturbance south of the Cape Verde Islands has become betterorganized, and is now Tropical Depression Seven. The convection isnot very deep at this time, but animation of visible images show agood circulation. In fact, earlier microwave data clearly depict amid-level center associated with the developing depression. Based onDvorak estimates from TAFB and SAB of 2.0 and 2.5, respectively, theinitial intensity has been set at 30 kt. No ASCAT data wereavailable at the time of this advisory.The environment appears to be favorable for gradual strengtheningduring the next 2 to 3 days. After that time, most of the globalmodels forecast a significant increase in shear. This should haltany additional strengthening, and most likely the cyclone willweaken or could even dissipate well east of the Lesser Antilles.The best estimate of the initial motion is toward the west or 280degrees at 12 kt. A moderately strong subtropical ridge is centerednorth of the depression. This pattern calls for a continuation ofa general westward track for the next 3 days. After that time,the ridge is expected to weaken, and the cyclone will likely turnmore toward the west-northwest with a decrease in forward speed.This is the solution of the models, except the ECMWF that does notacknowledge the existence of a cyclone.FORECAST POSITIONS AND MAX WINDSINIT 05/1500Z 12.3N 25.2W 30 KT 35 MPH 12H 06/0000Z 12.5N 26.9W 30 KT 35 MPH 24H 06/1200Z 12.8N 29.2W 35 KT 40 MPH 36H 07/0000Z 13.0N 32.0W 40 KT 45 MPH 48H 07/1200Z 13.5N 34.7W 45 KT 50 MPH 72H 08/1200Z 14.5N 40.0W 50 KT 60 MPH 96H 09/1200Z 15.0N 45.5W 45 KT 50 MPH120H 10/1200Z 15.5N 50.0W 40 KT 45 MPH$$Forecaster Avila
000WTNT42 KNHC 060840TCDAT2TROPICAL STORM GRACE DISCUSSION NUMBER 4NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015500 AM AST SUN SEP 06 2015Deep convection has become better organized during the past severalhours, with a more pronounced curved band developing to the westand south of the center. Recent microwave imagery, especially a0331 UTC GCOM pass, showed a surprisingly well-organized inner core,with the low-level center located a little farther south thanprevious estimates. Subjective Dvorak estimates are T3.0/45 kt fromTAFB and T2.5/35 kt from SAB, and the initial intensity is thereforeraised to 40 kt. If Grace is as well organized as suggested by themicrowave data, this intensity could be conservative.With the slight southward adjustment of the initial position, theestimated motion is now 270/11 kt. Grace is located due south of amid-tropospheric anticyclone, and a ridge axis extends westwardacross the Atlantic to north of the Lesser Antilles. This patternis expected to change little during the forecast period, whichshould keep Grace on a general westward path through day 5. Theguidance is in generally good agreement, and the updated NHC trackis shifted a little bit south of the previous forecast, mainly toaccount for the adjusted initial position. This solution is abit south of the TVCN model consensus and leans closest to theGFS, HWRF, and the Florida State Superensemble.Grace will be moving through a low-shear environment for the next36 to 48 hours, which is likely to support additional strengtheningwhile it moves westward over the tropical eastern Atlantic.Between days 3 through 5, while Grace is moving over the centraltropical Atlantic, vertical shear is forecast to increase to over20 kt and veer from southwesterly to westerly by the end of theforecast period. Such a hostile environment should induce weakeningbeginning on day 3. The new NHC intensity forecast indicatescontinued gradual strengthening through 36 hours while the shear islow and shows a slightly higher peak intensity than the previousforecast. Weakening could be fast once the shear sets in, and theday 4 and 5 intensities are unchanged from before.FORECAST POSITIONS AND MAX WINDSINIT 06/0900Z 12.4N 28.5W 40 KT 45 MPH 12H 06/1800Z 12.6N 30.8W 45 KT 50 MPH 24H 07/0600Z 12.8N 33.6W 50 KT 60 MPH 36H 07/1800Z 13.1N 36.3W 55 KT 65 MPH 48H 08/0600Z 13.4N 39.1W 55 KT 65 MPH 72H 09/0600Z 14.0N 44.7W 50 KT 60 MPH 96H 10/0600Z 14.5N 50.5W 40 KT 45 MPH120H 11/0600Z 15.5N 55.5W 35 KT 40 MPH$$Forecaster Berg