Tropical Storm Nicholas

Tropical Depression Nicholas Track 2200 Hours September 14 2021
Tropical Depression Nicholas Track 2200 Hours September 14 2021

Tropical Storm Nicholas Rainfall ForecastTropical Storm Nicholas – NWS National Hurricane Center Miami FL 1000 PM CDT Tue Sep 14, 2021 (see 10:00 video below)

Satellite imagery, radar data, and surface observation indicate that the center of Nicholas is over the Beaumont/Port Arthur area of southeastern Texas. The cyclone is currently comprised of a large swirl of low- to mid-level clouds and showers, with a few patches of deep convection well removed from the center. The initial intensity of 30 kt is based on a combination of Doppler radar data and surface obs, and these winds are mainly over water to the southeast of the center. Nicholas should continue to weaken due to strong shear, dry air entrainment, and land interaction, and the cyclone is forecast to degenerate to a remnant low after 24 h and dissipate completely by 72 h. It should be noted that some of the track guidance models show enough south of east motion to bring the center back over the Gulf of Mexico in a day or two. However, even if this should occur the shear and dry air should prevent any re-development. The initial motion is 060/5. While there is some spread in the guidance, it generally agrees on a slow eastward motion for 36 h or so, followed by a northward drift. The new forecast track has only minor changes from the previous track. Although the winds associated with Nicholas are subsiding, due to the forecast slow motion, heavy rainfall and a significant flash flood risk will continue along the Gulf Coast for the next couple of days.

The is the last advisory on Nicholas issued by the National Hurricane Center. 

Key Messages:

  • 1. Heavy rainfall will impact areas across southern and central Louisiana, southern Mississippi, far southern Alabama, and the western Florida Panhandle through early Friday. Significant rainfall amounts are expected, potentially resulting in areas of life-threatening flash and urban flooding across these areas. Widespread minor to isolated moderate river flooding is also possible.
  • 2. Storm surge inundation along the coasts of upper Texas and southwestern Louisiana will diminish tonight. 3. Wind gusts to tropical-storm force are possible for a few more hours along portion of the Louisiana and upper Texas coasts.
  • 3. Wind gusts to tropical-storm force are possible for a few more hours along portion of the Louisiana and upper Texas coasts.
FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 30.0N  94.1W   30 KT  35 MPH - Depression (ESE Beaumont,TX)
 12H  15/1200Z 30.2N  93.6W   25 KT  30 MPH - Depression (WNW Vinton,LA)
 24H  16/0000Z 30.2N  92.9W   25 KT  30 MPH - Depression (ESE Lacassine,LA)
 36H  16/1200Z 30.4N  92.6W   20 KT  25 MPH - Post Tropical (WSW Basile,LA)
 48H  17/0000Z 30.9N  92.6W   15 KT  15 MPH - Post Tropical (ESE Blanche,LA)
 60H  17/1200Z 31.5N  92.6W   15 KT  15 MPH - Post Tropical (ENE Rock Hill,LA)
 72H  18/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Tue Sep 14, 2021

Doppler weather radar data from Houston and Lake Charles, along with surface observations, indicate that the intensity of Nicholas has remained steady over the past several hours despite having moved a little farther inland over the upper Texas coastal plain. Both satellite and radar data also indicate that the overall circulation has tightened up somewhat, although a large swath of stable low clouds have advected into most of the southern semicircle of Nicholas’ circulation. The highest sustained wind speeds of 34-36 kt have occurred in a narrow band of fragmented, shallow convection between Sabine Pass, Texas, and Cameron, Louisiana, during the past couple of hours.

Doppler radar velocity data from Lake Charles has also indicated wind speeds of 40-45 at 3,000 ft altitude just offshore the southwestern coast of Louisiana. Based on these wind data, the initial intensity is set at 35 kt. The estimated central pressure of 1003 mb is based on nearby surface observations, especially the reports from the Eagle Point, Texas, C-MAN station, which indicate that the center of Nicholas passed over or near that station between 1800-1900 UTC. As Nicholas moves farther inland, gradual weakening is forecast due to land interaction, entrainment of drier and more stable low- and mid-level air, and strong westerly vertical wind shear in excess of 30 kt. Nicholas is forecast to become a tropical depression later this evening and degenerate into a remnant low by late Wednesday or early Thursday.

The initial motion estimate is east-northeastward or 070 degrees at 5 kt. Nicholas is forecast by most of the global and regional models continue its east-east-northeastward motion through tonight, followed by an eastward motion at a slower forward speed on Wednesday and Thursday. Nicholas could still stall over southwestern or central Louisiana as the low-level steering flow collapses on Thursday. The new NHC track forecast is similar to the previous advisory track, and lies near the consensus track models TCVA and NOAA-HCCA.

Although the winds associated with Nicholas will gradually subside, heavy rainfall and a significant flash flood risk will continue along the Gulf Coast for the next couple of days.

Key Messages:

  • 1. Heavy rainfall will impact areas across southern and central Louisiana, southern Mississippi, far southern Alabama, and the western Florida Panhandle through early Friday. Significant rainfall amounts are expected, potentially resulting in areas of life-threatening flash and urban flooding across these areas. Widespread minor to isolated moderate river flooding is also possible.
  • 2. Storm surge inundation along the coasts of upper Texas and southwestern Louisiana will gradually diminish into tonight.
  • 3. Tropical storm conditions in the warning area long portions of the upper Texas and southwestern Louisiana coasts will gradually subside by this evening.
FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 29.6N  94.6W   35 KT  40 MPH - Tropical Storm (ESE Houston,TX)
 12H  15/0600Z 29.8N  94.0W   25 KT  30 MPH - Depression (ESE Hardin,TX)
 24H  15/1800Z 30.0N  93.2W   25 KT  30 MPH - Depression (ESE Buna,TX)
 36H  16/0600Z 30.1N  92.8W   20 KT  25 MPH - Post Tropical (ENE Gillis,LA)
 48H  16/1800Z 30.5N  92.4W   15 KT  15 MPH - Post Tropical (WNW Kinder,LA)
 60H  17/0600Z 30.9N  92.4W   15 KT  15 MPH - Post Tropical (WNW Elizabeth,LA)
 72H  17/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Tue Sep 14, 2021 

Doppler weather radar data from Houston and Lake Charles, along with surface observations, indicate that Nicholas has continued to weaken while moving farther inland. The strongest winds recently reported near the Texas and Louisiana coasts have been 33-35 kt at a TCOON observing station near Sabine Pass, Texas. The strongest winds over water south of southwestern Louisiana are based on Doppler radar average velocities of 45-50 kt between 5000-7500 ft. Based on these wind data, the initial intensity has been lowered to 40 kt. The estimated central pressure of 1002 mb is based on nearby surface observations in the Houston metropolitan area. Further weakening is expected as Nicholas moves farther inland due to frictional effects, entrainment of very dry mid-level air from the southern Plains, and increasing southwesterly to westerly shear. The latter condition is expected to cause the low- and upper-level circulation to decouple in about 24 hours, which will hasten the weakening process. No significant changes were made to the previous intensity forecast, and Nicholas is now expected to become a tropical depression by tonight and degenerate into a remnant low by late Wednesday.

Nicholas is now moving northeastward or 050 degrees at a slower forward speed of 5 kt. The cyclone should gradually turn toward the east-northeast by tonight, and move eastward more slowly on Wednesday and Thursday. It is possible that Nicholas could stall over southwestern or central Louisiana as the low-level steering flow collapses. The new NHC track forecast is similar to but slightly slower than the previous advisory tack.

Although the winds associated with Nicholas will be weakening, heavy rainfall and a significant flash flood risk will continue along the Gulf Coast during the next couple of days.

Key Messages:

  • 1. Heavy rainfall will impact areas from the upper coast of Texas, across Louisiana, southern Mississippi, far southern Alabama and the western Florida Panhandle through Thursday. Significant rainfall amounts are expected, potentially resulting in areas of life-threatening flash and urban flooding across these areas. Minor to isolated major river flooding is also possible in smaller river basins and urban areas.
  • 2. There is the danger of life-threatening storm surge inundation along the coast of Texas from Port Bolivar to Sabine Pass. Residents in these areas should follow any advice given by local officials.
  • 3. Tropical storm conditions are expected to continue along the Louisiana coast into this afternoon. Tropical storm conditions in the warning area across the upper Texas coast will diminish this afternoon as Nicholas moves farther to the northeast.
FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 29.6N  95.3W   40 KT  45 MPH - Tropical Storm (ESE Houston,TX)
 12H  15/0000Z 30.1N  94.7W   30 KT  35 MPH - Depression (ESE Hardin,TX)
 24H  15/1200Z 30.4N  93.9W   25 KT  30 MPH - Depression (ESE Buna,TX)
 36H  16/0000Z 30.4N  93.2W   25 KT  30 MPH - Depression (ENE Gillis,LA)
 48H  16/1200Z 30.5N  92.8W   15 KT  15 MPH - Depression (WNW Kinder,LA)
 60H  17/0000Z 30.9N  92.8W   15 KT  15 MPH - Post Tropical (WNW Elizabeth,LA)
 72H  17/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 PM CDT Mon Sep 13, 2021

Very recently, a WeatherFlow Station at Matagorda Bay, Texas, reported sustained winds of 66 kt with a gust to 83 kt. Based on this observation, Nicholas is being upgraded to a hurricane on this advisory, and a Hurricane Warning is issued. No additional strengthening is anticipated until the system makes landfall, and gradual weakening is expected during the next 2-3 days while Nicholas moves over southeastern Texas and southwestern Louisiana.

Nicholas is moving north-northeastward, or around 020/10 kt. The system is currently moving through a weakness in the mid-level subtropical ridge. Within 12 to 24 hours, after Nicholas has moved inland, the ridge is forecast to weaken and leave Nicholas in an area of light steering currents. As a result, during the next couple of days, the cyclone is expected to turn eastward and slow to a crawl near southwestern Louisiana. The official forecast is slower than the previous one, but not as slow as the new model consensus.

Key Messages:

  • 1. Heavy rainfall will impact portions of southeastern Texas, Louisiana, and southern Mississippi through the middle of the week. Significant rainfall amounts are expected, potentially resulting in areas of life-threatening flash and urban flooding, along the eastern Texas coast into southwestern Louisiana. Minor to isolated major river flooding is also possible in smaller river basins and urban areas.
  • 2. There is the danger of life-threatening storm surge inundation along the coast of Texas from Port Aransas to Sabine Pass. Residents in these areas should follow any advice given by local officials.
  • 3. Hurricane conditions are expected within the Hurricane Warning area and Tropical storm conditions are expected with the Tropical Storm Warning area along the Texas coast.
FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 28.4N  95.8W   65 KT  75 MPH - Category 1 (ESE Matagorda,TX)
 12H  14/1200Z 29.6N  95.4W   50 KT  60 MPH - Tropical Storm (WSW Houston,TX)
 24H  15/0000Z 30.2N  94.8W   35 KT  40 MPH - Tropical Storm (WNW Hardin,TX)
 36H  15/1200Z 30.3N  93.7W   30 KT  35 MPH - Depression (WSW Starks,LA)
 48H  16/0000Z 30.3N  93.3W   25 KT  30 MPH - Depression (WNW Westlake,LA)
 60H  16/1200Z 30.3N  93.0W   25 KT  30 MPH - Depression (ENE Iowa,LA)
 72H  17/0000Z 30.5N  92.5W   20 KT  25 MPH - Post Tropical (WNW Eunice,LA)
 96H  18/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Mon Sep 13, 2021 

Corrected third paragraph typo Earlier reconnaissance aircraft flight-level wind data, along with recent Doppler radar velocity data from Brownsville and Corpus Christi, indicate that the inner-core wind field has still not consolidated into a single low-level wind center. High-resolution 1-minute GOES-16 visible satellite imagery, radar data, and reconnaissance wind data all indicate at least three small but very tight swirls revolving counter-clockwise around a mean center. An eye feature has tried to form on multiple occasions, only to dissipate after less than half an hour. An Air Force Reserve Hurricane Hunter aircraft sampled the most of the northeastern quadrant of Nicholas’ larger circulation this morning and afternoon, and measured 63-67-kt 850-mb flight-level winds, which roughly equals 53-54-kt surface winds in that quadrant; the aircraft also found SFMR surface winds of 50-51 kt in the same area. In addition, Doppler velocity data from Corpus Christi and Brownsville have been indicating average velocities of 59-60 kt between 9,000-10,000 ft near the center, which also equates to about 53-54-kt surface winds. Based on these wind data, the advisory intensity has been increased to 55 kt.

The initial motion estimate is 015/10 kt. The new NHC model guidance has come into better agreement on Nicholas moving toward the north- northeast until landfall occurs, now that the 12Z ECMWF model has made a significant eastward shift closer to the previous and current GFS and HWRF model solutions. After landfall, Nicholas is expected to move around the northwestern periphery of a deep-layer subtropical ridge that is oriented east-to-west across the central and eastern Gulf of Mexico. The latest guidance has continued to trend more eastward through 24 hours, followed by a more southward or right-of-track trend thereafter. As a result, the new NHC track forecast has followed suit, and has also been shifted a little to the right of the previous advisory track, and lies between the tightly packed consensus models to the west and the GFS model to the east.

Doppler velocity data from the Houston WSR-88D radar has shown a large swath of hurricane-force wind speeds in the northeastern quadrant of Nicholas’ circulation above 12,000 ft during the past couple of hours, with brief appearances of average velocities of 80-100 kt at high altitudes. Thus, there is an abundance of large-scale cyclonic vorticity available for another burst of intense convection to tap into, which could allow Nicholas to approach hurricane strength by landfall. This would most likely occur tonight during the convective maximum period near landfall where increased frictional convergence along the coast could aid in the development of convection on the west side of the circulation. After landfall, rapid weakening is expected owing to land interaction, strong southwesterly vertical wind shear in excess of 30 kt, and entrainment of mid-level dry air from the southern Plains. As a result of these negative conditions, Nicholas is forecast to weaken to tropical depression by late Tuesday and degenerate into a remnant low on Wednesday.

Key Messages:

  • 1. Heavy rainfall will impact portions of southeastern Texas, Louisiana, and southern Mississippi through the middle of the week. Significant rainfall amounts are possible, potentially resulting in areas of life-threatening flash and urban flooding, especially in highly urbanized metropolitan areas. Minor to isolated moderate river flooding is also expected, along with isolated major river flooding across smaller river basins and urban areas.
  • 2. There is the danger of life-threatening storm surge inundation along the coast of Texas from Port Aransas to Sabine 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 this evening, and could be near hurricane intensity at landfall. Tropical storm conditions are expected along portions of the middle and upper Texas coasts this evening and tonight, with hurricane conditions possible from Port Aransas to San Luis Pass.
FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 27.4N  96.4W   55 KT  65 MPH - Tropical Storm (ESE Mustang Island,TX)
 12H  14/0600Z 28.7N  96.1W   60 KT  70 MPH - Tropical Storm (ESE Palacios,TX)
 24H  14/1800Z 29.9N  95.3W   40 KT  45 MPH - Tropical Storm (WNW Houston,TX)
 36H  15/0600Z 30.4N  94.4W   30 KT  35 MPH - Depression (WNW Kountze,TX)
 48H  15/1800Z 30.9N  92.9W   25 KT  30 MPH - Depression (WSW Dido,LA)
 60H  16/0600Z 31.1N  91.4W   20 KT  25 MPH - Depression (WNW Donegal,MS)
 72H  16/1800Z 32.0N  90.6W   20 KT  25 MPH - Post Tropical (ENE Willing,MS)
 96H  17/1800Z...DISSIPATED

NWS National Hurricane Center Miami 1000 AM CDT Mon Sep 13, 2021 

Doppler radar data from Brownsville and Corpus Christi, Texas, along with reconnaissance aircraft flight-level wind data, indicate that Nicholas’ inner-core structure has undergone some radical changes since the previous advisory. The earlier near-eyewall pattern dissipated a few hours ago, and has been replaced with what appears to be an ongoing reformation of a new center abut 90 nmi north-northeast of the old center. The aircraft recently found a pressure of 1000 to 1002 mb with the dissipating original center, while Doppler radar velocity data show a pronounced mid- to upper-level circulation forming farther north as previously mentioned. The Air Force Reserve Hurricane Hunter aircraft is going to be concentrating its reconnoiter mission in Nicholas’ northeastern quadrant to see if reformation of the low-level center is occurring beneath the mid-level circulation noted in radar data. The initial wind speed remains 50 kt based on recent aircraft 850-mb flight-level winds of 59 kt, which equates to about 47 kt equivalent surface winds.

The initial motion is an uncertain 005/10 kt due to the erosion and ongoing reformation of the center. Despite the recent inner-core erosion, the latest NHC model guidance remains in fairly good agreement on Nicholas moving northward through a weakness in the subtropical ridge. The GFS model has been performing exceptionally well with predicting the recent erosion and more northward reformation of the Nicholas’ center. The new NHC track forecast is similar to but slightly east or right of the previous advisory track, and lies along the eastern edge of the track consensus model envelope, which is to the left of the GFS track prediction.

Although the inner-core convective pattern has been disrupted, recent trends in the radar data suggest that a new center should reform farther northeast into the convective cloud shield. The latest GFS- and ECMWF-based SHIPS shear analyses indicate that westerly shear of near 20 kt is allegedly affecting Nicholas. However, water vapor satellite imagery suggests that the upper-level shear vector is actually from a south-southwesterly direction, which is more along than across the cyclone’s forward motion, thus reducing the magnitude and negative effects of the vertical wind shear. Therefore, strengthening is still expected until landfall as Nicholas continues to move over slightly warmer Gulf waters. It is possible that Nicholas could become a hurricane just before landfall, and that’s the reason for the northeastward extension of the hurricane watch area. Nicholas should rapidly weaken after landfall due to increased frictional effects, strong southwesterly shear, and entrainment of mid-level dry air, resulting in degeneration into a tropical depression by late Tuesday and a remnant low on Wednesday. Otherwise, no significant changes were made to the previous advisory intensity forecast.

Key Messages:

  • 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 life-threatening flash and urban flooding, especially in highly urbanized metropolitan areas. Minor to isolated 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 Sabine 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 by this evening, and could be near hurricane intensity at landfall. Tropical storm conditions are expected along portions of the middle Texas coast beginning this afternoon, with hurricane conditions possible from Port Aransas to San Luis Pass by late afternoon through tonight.
  • 4. Tropical storm conditions are expected along portions of the coast of south Texas into the afternoon.
FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 26.4N  96.8W   50 KT  60 MPH - Tropical Storm (ESE South Padre Island,TX)
 12H  14/0000Z 27.5N  96.7W   60 KT  70 MPH - Tropical Storm (ESE Mustang Island,TX)
 24H  14/1200Z 29.1N  96.3W   45 KT  50 MPH - Tropical Storm (ESE Louise,TX)
 36H  15/0000Z 30.2N  95.4W   30 KT  35 MPH - Depression (ESE Woodloch,TX)
 48H  15/1200Z 31.0N  94.0W   25 KT  30 MPH - Depression (WNW Jasper,TX)
 60H  16/0000Z 31.5N  92.5W   20 KT  25 MPH - Depression (WSW Bentley,LA)
 72H  16/1200Z 32.0N  91.1W   20 KT  25 MPH - Post Tropical (WSW Grand Gulf,MS)
 96H  17/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 PM CDT Sun Sep 12, 2021

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.

Key Messages:

  • 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.
FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 22.5N  95.5W   35 KT  40 MPH - Tropical Storm (ENE Tampico,MX)
 12H  13/1200Z 24.7N  96.5W   45 KT  50 MPH - Tropical Storm (ENE El Mezquital,MX)
 24H  14/0000Z 27.0N  96.5W   50 KT  60 MPH - Tropical Storm (ESE Mustang Island,TX)
 36H  14/1200Z 28.6N  96.1W   55 KT  65 MPH - Tropical Storm (WSW Matagorda,TX)
 48H  15/0000Z 29.9N  95.4W   45 KT  50 MPH - Tropical Storm (WNW Aldine,TX)
 60H  15/1200Z 30.4N  94.8W   40 KT  45 MPH - Tropical Storm (WSW Rye,TX)
 72H  16/0000Z 31.0N  94.0W   30 KT  35 MPH - Depression (WNW Jasper,TX)
 96H  17/0000Z 31.7N  92.0W   20 KT  25 MPH - Post Tropical (ENE Jena,LA)
120H  18/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Sun Sep 12, 2021

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.

Key Messages:

  • 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.
FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 22.8N  95.5W   35 KT  40 MPH - Tropical Storm (ENE Tampico,MX)
 12H  13/0600Z 24.4N  96.3W   45 KT  50 MPH - Tropical Storm (ENE La Pesca,MX)
 24H  13/1800Z 26.7N  96.9W   55 KT  65 MPH - Tropical Storm (ENE Arroyo City,TX)
 36H  14/0600Z 28.7N  96.8W   55 KT  65 MPH - Tropical Storm (ENE Placedo,TX)
 48H  14/1800Z 30.4N  96.3W   35 KT  40 MPH - Tropical Storm (ESE Wilcox,TX)
 60H  15/0600Z 31.2N  95.8W   30 KT  35 MPH - Depression (ESE Guys Store,TX)
 72H  15/1800Z 31.7N  95.2W   25 KT  30 MPH - Depression (WSW Rusk,TX)
 96H  16/1800Z 31.9N  94.7W   20 KT  25 MPH - Post Tropical (WSW Mt Enterprise,TX)
120H  17/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Sun Sep 12, 2021 

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.

Key Messages:

  • 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.
FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 20.5N  94.8W   35 KT  40 MPH - Tropical Storm (ESE Tecolutla,MX)
 12H  13/0000Z 21.9N  95.7W   40 KT  45 MPH - Tropical Storm (ESE Tampico,MX)
 24H  13/1200Z 24.1N  96.6W   45 KT  50 MPH - Tropical Storm (ENE La Pesca,MX)
 36H  14/0000Z 26.4N  96.9W   50 KT  60 MPH - Tropical Storm (ESE Port Mansfield,TX)
 48H  14/1200Z 28.2N  96.5W   55 KT  65 MPH - Tropical Storm (ESE Matagorda Island,TX)
 60H  15/0000Z 29.4N  95.9W   40 KT  45 MPH - Tropical Storm (WNW Needville,TX)
 72H  15/1200Z 30.3N  95.2W   30 KT  35 MPH - Depression (ESE Security,TX)
 96H  16/1200Z 31.0N  94.8W   25 KT  30 MPH - Depression (ENE Corrigan,TX)
120H  17/1200Z 32.0N  94.5W   20 KT  25 MPH - Post Tropical (ESE Dotson,TX)

NWS National Hurricane Center Miami FL 800 PM EDT Sat Sep 11, 2021

Corrected to change the order of the system northeast of the Azores.

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A tropical wave and an upper-level trough continue to produce a large area of disorganized showers and thunderstorms over portions of southeastern Mexico and the southern and central Gulf of Mexico. Upper-level winds are gradually becoming more conducive for development, and a tropical depression is likely to form on Sunday or Monday while the disturbance moves northwestward and then northward near the coast of northeastern Mexico. Additional development will be possible through the middle of next week if the system remains over water, and interests along the western and northwestern Gulf coast should monitor the progress of this system. An Air Force Hurricane Hunter aircraft is scheduled to investigate the system tomorrow, if necessary. Regardless of development, this disturbance will continue to produce heavy rain across portions of southern Mexico, including the western Yucatan Peninsula, through tonight which may lead to flash flooding and mudslides. By late Sunday, heavy rain is expected to reach portions of the Texas and Louisiana coasts with a heavy rain threat then continuing across those coasts through the middle of next week. Localized significant rainfall amounts are possible, potentially resulting in areas of flash, urban, and isolated river flooding. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.
  • 2. Showers and thunderstorms remain poorly organized in association with a tropical wave located near the Cabo Verde Islands. Environmental conditions are currently conducive for development, and a tropical depression could still form this weekend or early next week while the system moves westward over the far eastern Atlantic. By the middle of next week, stronger upper-level winds and marginally warm ocean temperatures are expected to limit additional development. Regardless of development, this disturbance is likely to bring gusty winds and locally heavy rain across the Cabo Verde Islands tonight. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…medium…50 percent.
  • 3. A non-tropical area of low pressure is located over the far northeastern Atlantic several hundred miles northeast of the Azores. This system is forecast to move south-southeastward towards warmer waters, which could allow the low to gradually acquire some tropical or subtropical characteristics by the middle of next week. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…20 percent.
  • 4. Another tropical wave is expected to move off the west coast of Africa in a few days. Gradual development of this system is possible thereafter, and a tropical depression could from by the middle of next week while it moves westward across the eastern tropical Atlantic Ocean. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.
  • 5. An area of low pressure is expected to form near the southeastern Bahamas in a few days resulting from moisture by a tropical wave interacting with an upper-level trough. Gradual development of this system is possible thereafter as it moves northwestward across the western Atlantic. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sat Sep 11, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Hurricane Larry, located over the Labrador Sea.

  • 1. A tropical wave and an upper-level trough are producing a large area of disorganized showers and thunderstorms over portions of Central America, southeastern Mexico, and the adjacent waters of the northwestern Caribbean Sea and southern Gulf of Mexico. Although upper-level winds are not conducive for development currently, they are expected to become more favorable for the system during the next day or so. A tropical depression is likely to form on Sunday or Monday while the disturbance moves northwestward and then northward near the coast of northeastern Mexico. Further development will be possible through the middle of next week if it remains over water, and interests along the western and northwestern Gulf coast should monitor the progress of this system. Regardless of development, this disturbance is expected to produce heavy rain across portions of Central America and the Yucatan Peninsula through today which may lead to flash flooding and mudslides. By late this weekend, heavy rain will likely reach portions of the western Gulf coast, including coastal Texas and Louisiana through the middle of next week. Localized significant rainfall amounts will be possible, potentially resulting in areas of flash and urban flooding. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…80 percent.
  • 2. A tropical wave continues to produce a concentrated area of showers and thunderstorms just southeast of the Cabo Verde Islands. Environmental conditions appear generally conducive for gradual development, and a tropical depression is likely to form late this weekend or early next week while the system moves westward over the far eastern Atlantic. Regardless of development, this system is likely to bring gusty winds and locally heavy rain across the Cabo Verde Islands later today and tonight. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.
  • 3. Another tropical wave is expected to move off the west coast of Africa in a few days. Some development of this system will be possible through the middle of next week while it moves westward across the eastern tropical Atlantic Ocean. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...20 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Fri Sep 10 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Hurricane Larry, located over the western Atlantic several hundred miles southwest of Newfoundland, Canada.

  • 1. The northern portion of a tropical wave is producing disorganized showers and thunderstorms over Honduras, the western Caribbean Sea, and portions of the Yucatan peninsula. This system is forecast to move into the Bay of Campeche and merge with a pre-existing surface trough located over the southwestern Gulf of Mexico by this weekend. Environmental conditions are expected to be conducive to support gradual development, and a tropical depression is likely to form Sunday or Monday before the system moves onshore along the western Gulf of Mexico coast. Regardless of development, this disturbance is expected to produce heavy rains across portions of Central America through Saturday. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high...70 percent.
  • 2. A strong tropical wave is expected to emerge off of the west coast of Africa by tonight. Environmental conditions are forecast to be conducive for gradual development thereafter, and a tropical depression is likely to form late this weekend or early next week as the system moves west-northwestward over the far eastern Atlantic near the Cabo Verde Islands. Interests in the Cabo Verde Islands should monitor the progress of this system. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Thu Sep 9, 2021

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Hurricane Larry, located over the western Atlantic a few hundred miles east-southeast of Bermuda, and on Tropical Depression Mindy, located inland over southeastern Georgia.

  • 1. The northern portion of a tropical wave over northeastern Honduras and the western Caribbean Sea is forecast to emerge over the southern Bay of Campeche on Saturday. Environmental conditions are expected to be conducive to support some gradual development of the system before it moves over mainland Mexico early next week. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.
  • 2. A strong tropical wave is expected to emerge off of the west coast of Africa on Saturday. Environmental conditions are forecast to be conducive for development thereafter, and a tropical depression could form by early next week as it moves west-northwestward over the far eastern Atlantic near the Cabo Verde Islands. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

Recent Tropical Cruise Weather:

Video: Extreme lightning with HURRICANE NICHOLAS Matagorda Bay to Surfside Beach, Texas!