1. Tropical storm conditions are expected along portions of the northeastern coast of Mexico and the coast of south Texas beginning on Monday. Nicholas is forecast to approach the middle Texas coast as a strong tropical storm on Tuesday, and tropical storm conditions are possible along portions of the middle and upper Texas coasts late Monday night and Tuesday.

2. There is the possibility of life-threatening storm surge along the coast of Texas from the Mouth of the Rio Grande to High Island. Residents in these areas should follow any advice given by local officials.

3. Periods of heavy rainfall are expected to impact portions of the Texas and Louisiana coasts today through the middle of the week. Significant rainfall amounts are possible, potentially resulting in areas of flash, urban, and isolated river flooding.

1. Periods of heavy rainfall are expected to impact portions of the Texas and Louisiana coasts today 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 Sargent 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:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- Mouth of the Rio Grande to Port Aransas Texas
- Barra el Mezquital to the U.S./Mexico border

A Storm Surge Watch is in effect for...
- Mouth of the Rio Grande to High Island Texas

A Tropical Storm Watch is in effect for...
- North of Port Aransas to High Island Texas

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 lifethreatening 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 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 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 5 to 10 inches, with isolated maximum amounts of 15 inches, across portions of coastal Texas into southwest Louisiana today through the middle of the week. This rainfall may produce areas of flash, urban, and isolated river flooding.

Over the eastern portions of the Mexican state of Tamaulipas rainfall amounts of 2 to 5 inches can be expected today 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...

Mouth of the Rio Grande to High Island, TX...24 ft Baffin Bay, Corpus Christi Bay, Aransas Bay, San Antonio Bay, Matagorda Bay, and Galveston Bay...24

The deepest water will occur along the immediate coast in areas of onshore flow, where the surge will be accompanied by large and dangerous waves. Surgerelated 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 by Monday afternoon, making outside preparations difficult or dangerous. Tropical storm conditions are possible within the watch area by late Monday night or early Tuesday.

At 100 PM CDT (1800 UTC), the center of Tropical Storm Nicholas was near latitude 21.7 North, longitude 95.5 West. Nicholas is moving toward the northnorthwest near 15 mph (24 km/h). Satellite and reconnaissance aircraft data suggest that the center may be reforming farther north. As a result, some erratic motion is possible this afternoon, but a general northnorthwestward motion near 15 mph (24 km/h) should resume later today. This motion should then continue through tonight. A slower northward or northnortheastward 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 late Monday, and approach the south or central Texas coast Monday night or early Tuesday.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Gradual strengthening is forecast while Nicholas approaches the northwestern Gulf coast during the next day or so.

Tropicalstormforce winds extend outward up to 105 miles (165 km) from the center.

The estimated minimum central pressure is 1008 mb (29.77 inches).

Showers and thunderstorms associated with a broad area of low pressure over the southern Bay of Campeche have increased overnight and very recently become better organized with a loose band of convection around the northeastern portion of the circulation. An Air Force Reserve reconnaissance aircraft that has been investigating the system has found 44-kt flight-level winds and SFMR winds that support a 35-kt initial intensity. Based on the recent increase in organization and the 35-kt initial intensity, advisories are being initiated on Tropical Storm Nicholas, the fourteenth named storm of the Atlantic hurricane season.

The storm is located within an environment of moderate south-southwesterly vertical wind shear, over warm waters, and in a moist and unstable atmosphere. These conditions should allow gradual strengthening over the next 24 to 48 hours. The NHC intensity forecast follows suit and calls for gradual strengthening until the system reaches the coast of Texas. The official wind speed forecast is near the higher end of the guidance in best agreement with the SHIPS statistical guidance, the HFIP corrected consensus, and the HWRF. In this case, the intensity forecast is highly dependent on eventual track of the system. A track to the east of the NHC forecast could result in a lower wind shear environment and slightly more time over water for the system to strengthen. Conversely a track to the west of the forecast track would result in the system interacting with land much sooner.

Since the system is still in its formative stage the initial motion estimate is a somewhat uncertain 330/11 kt. A north-northwestward motion around the western portion of a mid-level ridge that is sliding east near the coast of the Carolinas, should continue to steer Nicholas in that direction for the next 24 to 48 hours. After that time, steering currents weaken and the cyclone is expected to move slowly north-northeastward between a couple of mid-level ridges located to the east and west of Nicholas. The track guidance generally agrees with this overall scenario but there is some cross-track spread with the UKMET along the left side of the guidance envelope taking the storm into northeastern Mexico, while the GFS, HWRF, and HMON are along the right side. The NHC track is near the various consensus models and both the EC and GFS ensemble means.

Visible satellite imagery, scatterometer wind data, and earlier reconnaissance aircraft observations indicate that the circulation of Nicholas is elongated from northwest to southeast. In fact, visible satellite imagery and the aircraft data has shown that there have been several low-level swirls rotating about a mean center. This is not surprising since the tropical cyclone is still in its formative stage. The Air Force plane did not find winds any stronger than they did this morning and the ASCAT data revealed peaks winds of around 30 kt. Given the typical undersampling of the scatterometer instrument, the earlier aircraft data, and peak one-minute wind observations of 31 kt from NOAA buoy 42055 earlier today, the intensity remains 35 kt for this advisory.

Nicholas will be moving over the warm waters of the western Gulf of Mexico during the next day or so, and this combined with a moist, unstable atmosphere favors strengthening. The primarily inhibiting factor appears to be moderate south-southwesterly vertical wind shear caused by an upper-level trough over northern Mexico. The trough is forecast to move westward and weaken during the next day or so, which could allow for a more favorable upper-level wind pattern later tonight and Monday. The NHC intensity forecast again calls for strengthening while the system moves toward the northwest Gulf coast, but the main uncertainty regarding the intensity forecast is how much time the cyclone will spend over the Gulf waters. The GFS and HWRF models, which depict a track farther east, show significantly more strengthening than the UKMET and ECMWF models which show a weaker tropical cyclone moving inland over northeastern Mexico or southern Texas much sooner. The NHC intensity forecast is similar to the previous advisory, but indicates a faster rate of strengthening during the next 12-24 hours. Although not explicitly shown in the intensity forecast, Nicholas could approach hurricane strength when it nears the northwest Gulf coast, especially if it moves to the right of the NHC forecast track and spends more time over water. Due to this uncertainty a Hurricane Watch has been issued a for a portion of the Texas coast. The NHC forecast is in best agreement with the SHIPS and HFIP corrected consensus model, but is not as high as the latest HWRF.

The center of Nicholas appears to have re-formed farther north since this morning and the initial motion estimate is again a somewhat uncertain 340/12 kt. The track forecast reasoning has not changed from this morning. Nicholas should move north-northwestward to northward during the next day or so around the western portion of a mid-level ridge that is located near the southeast U.S. coast. The latest runs of the various dynamical models have shown typical variability, but the overall guidance envelope has not changed too much through the first 36 hours. The GFS has been the most consistent model and its 12Z run was fairly close to the previous NHC track forecast. Therefore, the NHC track leans along the right side of the guidance envelope between the HWRF and GFS, which are a little to the right of the consensus aids. Due to the acute angle of approach of Nicholas to the coast, users are reminded to not focus on the exact forecast track as small changes in the heading of the cyclone could result in differences in both the location and timing of landfall. Regardless of where Nicholas makes landfall, storm surge, wind, and rainfall impacts are likely over a large portion of northeastern Mexico and Texas coastal areas. After landfall, a slower north-northeastward motion is forecast, and by 72 hours the cyclone is forecast to be located between a couple of mid-level ridges, which will likely result in weaker steering currents and an even slower northeastward motion. By day 5, the global model guidance suggest that the low-level circulation will become an open trough so dissipation is indicated at that time.