1. Periods of heavy rainfall are expected to impact portions of the Texas and Louisiana coasts through the middle of the week. Significant rainfall amounts are possible, potentially resulting in areas of considerable flash and urban flooding, especially in highly urbanized metropolitan areas. Isolated minor to moderate river flooding is also expected.

2. There is the danger of life-threatening storm surge inundation along the coast of Texas from Port Aransas to San Luis Pass. Residents in these areas should follow any advice given by local officials.

3. Nicholas is forecast to approach the middle Texas coast as a strong tropical storm late Monday and early Tuesday, and could be near hurricane intensity if it moves to the right of the forecast track and remains over water longer. Tropical storm conditions are expected along portions of the middle Texas coast beginning Monday afternoon, with hurricane conditions possible from Port Aransas to Freeport late Monday and Monday night.

4. Tropical storm conditions are expected along portions of the northeastern coast of Mexico and the coast of south Texas beginning Monday morning.

CHANGES WITH THIS ADVISORY: The Hurricane Watch has been extended eastward to Freeport Texas. The Tropical Storm Warning has been extended eastward to High Island Texas. The Tropical Storm Watch has been extended eastward to Sabine Pass. The Storm Surge Watch has been extended eastward to Rutherford Beach Louisiana. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for...
- Port Aransas to San Luis Pass Texas
- Aransas Bay, San Antonio Bay, and Matagorda Bay A Hurricane Watch is in effect for...
- Port Aransas to Freeport Texas A Tropical Storm Warning is in effect for...
- Mouth of the Rio Grande to High Island Texas
- Barra el Mezquital to the U.S./Mexico border A Storm Surge Watch is in effect for...
- Mouth of the Rio Grande to Port Aransas Texas
- San Luis Pass Texas to Rutherford Beach Louisiana, including Galveston Bay
- Baffin Bay and Corpus Christi Bay A Tropical Storm Watch is in effect for...
- East of High Island Texas to Sabine Pass A Storm Surge Warning means there is a danger of life threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Storm Surge Watch means there is a possibility of life threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical storm force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Interests elsewhere along the upper Texas coast and southwestern Louisiana should monitor the progress of this system. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service.

Key messages for Nicholas can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC and on the web at hurricanes.gov/graphics_at4.shtml?key_messages

RAINFALL: Nicholas is expected to produce storm total rainfall of 8 to 16 inches, with isolated maximum amounts of 20 inches, across portions of the middle and upper Texas coastal areas tonight through the middle of the week. Across the rest of coastal Texas into southwest Louisiana rainfall of 5 to 10 inches is expected. This rainfall may produce areas of considerable flash and urban flooding, especially in highly urbanized metropolitan areas. Additionally, there is the potential for isolated minor to moderate river flooding. Over the northeastern portions of the Mexican state of Tamaulipas, rainfall amounts of 2 to 5 inches can be expected tonight into Monday.

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide... Port O'Connor to San Luis Pass TX including Matagorda Bay... 3 5 ft San Luis Pass, TX to Rutherford Beach, LA including Galveston Bay...2 4 ft Mouth of the Rio Grande to Port O'Connor, TX...2 4 ft Baffin Bay, Corpus Christi Bay, Aransas Bay and San Antonio Bay...2 4 ft Rutherford Beach, LA to Intracoastal City, LA...1 3 ft Sabine Lake and Calcasieu Lake...1 3 ft The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and dangerous waves. Surge related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

WIND: Tropical storm conditions are expected to first reach the coast within the warning area in northeastern Mexico and southern Texas Monday morning, making outside preparations difficult or dangerous. These conditions will spread northward within the warning area through Monday night. Hurricane conditions are possible in the Hurricane Watch area Monday night. Tropical storm conditions are possible within the watch area by late Monday night or early Tuesday.

TORNADOES: A tornado or two will be possible Monday into Monday night across the middle and lower Texas coast.

SURF: Swells generated by Nicholas will begin affecting portions of the northwest Gulf coast tonight and continue into Tuesday. These swells are likely to cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 1000 PM CDT (0300 UTC), the center of Tropical Storm Nicholas was located near latitude 22.5 North, longitude 95.5 West. Nicholas has been meandering or drifting northward near 2 mph (4 km/h) over the past couple of hours, but a north northwestward motion near 12 mph (19 km/h) is expected to resume by early Monday. A northward or north northeastward motion is forecast by late Monday or Monday night. On the forecast track, the center of Nicholas will pass near or just offshore the coasts of northeastern Mexico and South Texas on Monday, and move onshore along the coast of south or central Texas coast Monday night or early Tuesday. Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Strengthening is forecast until Nicholas reaches the northwest Gulf coast Monday night or early Tuesday. Tropical storm force winds extend outward up to 115 miles (185 km) from the center. The estimated minimum central pressure is 1007 mb (29.74 inches).

Nicholas is not yet a well-organized tropical cyclone, with little evidence of convective banding features on satellite imagery. Observations from the Air Force Hurricane Hunter aircraft indicate that the center is still not very well-defined, and appears to have reformed again, this time farther south. Data from the aircraft indicate that the central pressure has not changed much since earlier today, and the maximum winds remain near 35 kt. This is above the latest Dvorak intensity estimates from TAFB and SAB.

Nicholas will be traversing very warm waters during the next day or so, and within a moist, unstable atmosphere. These factors would favor strengthening. However, moderate southwesterly shear associated with an upper-level trough over northern Mexico could be an inhibiting factor for strengthening. In spite of the shear, the GFS model forecasts the system to strengthen while it nears the Texas coast. The official intensity forecast is at the upper end of the current model guidance. Given the uncertainties in the future strength of Nicholas, a Hurricane Watch is in effect for a portion of the Texas coast.

The current location of Nicholas is quite uncertain since the aircraft-reported center position is within a broad area of light winds and is well south of most of the deep convection. Although the fixes show little motion this evening, based on the model predictions, it appears likely that the center will shift or re-form significantly northward as early as Monday morning. This is at least partially accounted for in the latest NHC track forecast, but some northward adjustments are possible over night. The storm is expected to move toward a weakness in the subtropical ridge during the next 36 hours or so. The track guidance and the model consensus has shifted eastward somewhat since the earlier advisory package. This has necessitated an eastward shift in the official track, and a northeastward extension of the watches and warnings.