1. Heavy rainfall will 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 today, and could be near hurricane intensity at landfall. Tropical storm conditions are expected along portions of the middle Texas coast beginning by this afternoon, with hurricane conditions possible from Port Aransas to Freeport this afternoon and tonight.

4. Tropical storm conditions are expected along portions of the northeastern coast of Mexico and the coast of south Texas beginning during the next few hours.

CHANGES WITH THIS ADVISORY: None. 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. 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 Tropical Storm Watch means that tropical storm conditions are possible within the watch area. 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 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.

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 this morning, making outside preparations difficult or dangerous. These conditions will spread northward within the warning area through tonight. Hurricane conditions are possible in the Hurricane Watch area as early as this afternoon. Tropical storm conditions are possible within the watch area by tonight or early Tuesday.

TORNADOES: A tornado or two will be possible today into tonight across the Texas coast.

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

At 400 AM CDT (0900 UTC), the center of Tropical Storm Nicholas was located near latitude 25.5 North, longitude 96.6 West. Nicholas is moving toward the north northwest near 14 mph (22 km/h). The storm should turn northward later today and north northeastward on Tuesday. On the forecast track, the center of Nicholas will pass near or just offshore the coasts of northeastern Mexico and south Texas this morning, and move onshore along the coast of south or central Texas Monday afternoon or evening. Maximum sustained winds remain near 60 mph (95 km/h) with higher gusts. Strengthening is forecast today, and Nicholas could reach the northwest Gulf coast as a hurricane. Weakening is anticipated on Tuesday and Wednesday over land. Tropical storm force winds extend outward up to 115 miles (185 km) from the center. The estimated minimum central pressure is 1001 mb (29.56 inches).

Radar data from Brownsville shows that the center of Nicholas is on the southwestern side of a large area of deep convection over the western Gulf of Mexico. While southwesterly shear continues to affect the storm, the radar presentation has recently improved, with what could be the start of a partial eyewall forming in the northern quadrant. The initial wind speed remains 50 kt based on earlier aircraft flight-level winds of 59 kt, believable SFMR values up to 50 kt, along with radar winds at 5000 ft near 60 kt.

The storm is moving north-northwestward at about 12 kt. Nicholas is forecast to turn northward soon into a weakness in the subtropical ridge. The track prediction is only nudged slightly westward from the previous one through landfall, consistent with recent model guidance. Thereafter, there isn't good agreement among the models on how quickly the tropical cyclone will move northeastward out of Texas. Generally the models are faster this cycle, which seems believable given the large northward re-formation earlier likely exposing Nicholas to stronger mid-latitude flow. Thus the new NHC forecast is trended faster as well, but remains behind the model consensus. Obviously the forward speed is important to the heavy rainfall forecast, and this trend will be one to watch.

Nicholas should continue to strengthen up until landfall due primarily to the very warm Gulf waters and the recent inner-core improvements. Moderate southwesterly shear and some dry air are the main inhibiting factors and will hopefully keep the strengthening in check. However, it is possible that Nicholas could become a hurricane before landfall, and that's the reason for the hurricane watch area. Nicholas should weaken after landfall, diminish into a tropical depression within a couple of days, and degenerate into a remnant low in about 3 days. No significant changes were made to the previous NHC wind speed prediction.