Atlantic/2015/02L/Archive/1

## Public Advisory

TROPICAL STORM BILL SPECIAL ADVISORY NUMBER 1

WIKI-HURRICANES FORECAST CENTER

11:00 AM CDT MON JUN 15 2015

...TROPICAL STORM BILL FORMS IN THE SOUTHERN GULF OF MEXICO...

SUMMARY OF 11:00 AM CDT...1600 UTC...INFORMATION

LOCATION...25.9N 92.6W

ABOUT 270 MI...435 KM SSE OF GALVESTON TEXAS

MAXIMUM SUSTAINED WINDS...45 KT...50 MPH...85 KM/H

MINIMUM BAROMETRIC PRESSURE... 1007 MB...29.74 INCHES

PRESENT MOVEMENT...WNW OR 275 DEGREES AT 5 KT...6 MPH...9 KM/H

DISCUSSION AND 48-HOUR OUTLOOK

At 11:00 am CDT, the center of newly-designated Tropical Storm Bill was located at 25.9N, 92.6W, or about 270 miles (435 km) southwest of Galveston, Texas. Maximum sustained winds were 45 knots (50 mph, 85 km/h), with higher gusts. The minimum barometric pressure was 1007 millibars (inHg; 29.74 inHg), and the system was moving west-northwest at 5 knots (6 mph, 9 km/h). Environmental conditions are expected to be generally favorable for steady intensification before the cyclone moves ashore the Texas coastline on Tuesday.

NEXT ADVISORY

Next complete advisory at 4:00 pm CDT.

$$

Forecaster TAWX14

## Discussion

TROPICAL STORM BILL SPECIAL DISCUSSION NUMBER 1

WIKI-HURRICANES FORECAST CENTER

11:00 AM CDT MON JUN 15 2015

A reconnaissance aircraft investigating the area of disturbed weather has determined that the low-level circulation has become sufficiently well-defined to be designated a tropical cyclone. The plane identified peak flight-level winds of 54 kt, with non-contaminated surface winds closer to 45 kt. As a result, the initial intensity has been set at 45 kt for this advisory. The overall convective appearance of Bill remains rather elongated on a north to south axis, and microwave imagery indicates largely disorganized convection primarily east of the center. However, convection is shifting over the newly found low-level center as shear decreases.

The environment that Bill is currently located in should be conducive for strengthening. However, Bill is not expected to have much time to strengthen before making landfall along the Texas coast, as the tropical cyclone is expected to have only about 24 hours before striking land, and even less time before it starts interacting with the Continental United States. A general consensus between models exists, and the current WHFC forecast track and intensity forecast uses the forecast consensus shifted northward to account for Bill's location further north than the last model initialization. Bill is expected to travel generally northwestward before curving northward through landfall. What is striking, however, is that several models have indicated unusual strengthening or abnormal intensity maintenance of Bill over North Texas or Oklahoma perhaps via baroclinic support, and this has been accounted for in the intensity forecast with a slow inland decay intensity forecast.

INIT 15/1600Z 25.9N 92.6W 45KT 50MPH

12HR 16/0000Z  27.3N 94.5W 50KT 60MPH

24HR 16/1800Z 28.8N 95.8W 50KT 60MPH ... AT LANDFALL NEAR MATAGORDA BAY

36HR 17/0000Z 30.7N 96.3W 35KT 40MPH ... INLAND

48HR 18/1800Z 32.6N 96.0W 30KT 35MPH ... INLAND

72HR 19/1800Z 35.6N 93.5W 25KT 30MPH ... INLAND/REMNANT LOW

$$

Forecasters TAWX14/TheAustinMan