Tropical Storm Beta

Tropical Storm Beta Track 1600 Hours Sepember 22 2020
Tropical Storm Beta Track 1600 Hours Sepember 22 2020

Tropical Storm Beta Wind Speed FieldTropical Storm BetaNWS National Hurricane Center Miami FL 400 PM CDT Tue Sep 22, 2020 (see Tues 5:30 video below)

High-resolution visible satellite imagery, surface observations, and NOAA Doppler weather radar data from San Antonio and Houston, Texas, indicate that Beta has continued to weaken. What convection remains is quite shallow with a few cloud tops only extending up to 25,000- 30,000 ft ASL, mainly near and northeast of the center. However, those low-topped showers are quite prodigious rain-producers with rainfall totals of 13-14 inches having been measured across portions of the Houston metropolitan area thus far.

The initial intensity of 25 kt is based on near-shore buoy and surface observing stations. The initial motion estimate is now 065/04 kt. A coastal convergence zone or trough has formed about 20-25 nmi inland from the Texas Gulf coast and, owing to the lack of any significant deep-layer steering flow, Beta is forecast to move slowly along that trough axis and remain inland throughout the forecast period as a result. The ECMWF and UKMET models move Beta rapidly northeastward after 48 hours, but that scenario seems to be overdone given the expected shallow nature of the cyclone. The new NHC official track forecast is similar to the previous advisory track and lies close to a blend of the various consensus models, except that I used the slower forward speed of the GFS model.

Since Beta is forecast to remain inland for the next throughout the forecast period, the cyclone is not expected to regain tropical storm status. Beta to degenerate into a remnant low by 36 hours, and dissipate over Mississippi or Alabama in 96 hours, if not sooner. The new intensity forecast is similar to the previous advisory and closely the simple and corrected-consensus models IVCN and HCCA.

This is the last NHC advisory on Beta.

Key Messages:

  • 1. Significant flash and urban flooding is occurring and will continue for the middle and upper Texas coast today. The slow motion of Beta will continue to produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and minor to isolated moderate river flooding is likely. Periods of rainfall will spread east into the Lower Mississippi Valley, portions of the Tennessee Valley, and the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible on smaller rivers.
  • 2. Persistent onshore flow will continue to result in above normal high tides, and coastal flooding over the next few days will be slow to recede. For information on the ongoing coastal flooding, please refer to coastal flood products issued by local National Weather Service offices.
FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 29.0N  96.3W   25 KT  30 MPH - Depression (WSW Danevang, Texas)
 12H  23/0600Z 29.3N  95.6W   25 KT  30 MPH - Depression (WNW Otey, Texas)
 24H  23/1800Z 30.1N  94.2W   25 KT  30 MPH - Depression (WNW Beaumont, Texas)
 36H  24/0600Z 31.3N  92.5W   20 KT  25 MPH - Low (WSW Alexandria, Louisiana)
 48H  24/1800Z 32.5N  90.8W   20 KT  25 MPH - Low (ESE Redwood, Mississippi)
 60H  25/0600Z 33.8N  88.9W   20 KT  25 MPH - Low (WNW Sparta, Mississippi)
 72H  25/1800Z 35.1N  87.3W   15 KT  15 MPH - Low (ESE Leoma, Tennessee)
 96H  26/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Tue Sep 22, 2020 

High-resolution visible satellite imagery, surface observations, and NOAA Doppler weather radar data from San Antonio, Corpus Christi, and Houston, Texas, indicate that Beta has moved a little farther inland and has weakened to a tropical depression. The same data also show that Beta has started a slow drift toward the northeast. Deep convection has waned considerably since the previous advisory, especially during the past few hours, with cloud tops now warmer than -30 deg C, which no longer meets the Dvorak satellite classification criterion. The initial intensity is 30 kt is based on average Doppler velocities of 35-40 kt between 1500-2500 ft ASL just to the southeast and south of Galveston.

The initial motion estimate is now 045/02 kt. Steering currents around Beta remain weak. However, water vapor imagery indicates that a broad mid- to upper-level trough over western Texas is moving slowly eastward, and that feature should gradually force Beta east-northeastward later today and tonight, followed by a faster motion toward the northeast on Wednesday and Thursday across Louisiana and Mississippi before dissipating in about 4 days. The new NHC forecast track is similar to the previous advisory track, which keeps Beta just inland from the Gulf coast, and lies near a blend of the simple consensus models TVCA and GFEX, and the NOAA corrected-consensus model HCCA. Since Beta’s center is forecast to remain just inland for the next 36-48 hours, chances of the cyclone regaining tropical storm status are becoming less likely. As a result, the new official intensity forecast shows Beta remaining a 25-30 kt depression during that time, followed by weakening to a remnant low by 48 hours, and dissipation over Mississippi or Alabama by 96 hours. This is consistent with the various simple and corrected-consensus models.

Although Beta is now an inland tropical depression, the National Hurricane Center will continue to issue advisories on the cyclone due to its proximity to the Gulf of Mexico and until it becomes clear that re-strengthening into a tropical storm is unlikely.

Key Messages:

  • 1. Significant flash and urban flooding is occurring and will continue for the middle and upper Texas coast today. The slow motion of Beta will continue to produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and minor to isolated moderate river flooding is likely. Periods of rainfall will spread east into the Lower Mississippi Valley and portions of the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible on smaller rivers.
  • 2. Persistent onshore flow will continue to result in above normal high tides, and coastal flooding over the next few days will be slow to recede. For information on the ongoing coastal flooding, please refer to coastal flood products issued by local National Weather Service offices.
FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 28.9N  96.7W   30 KT  35 MPH - Depression (ENE Inez, Texas)
 12H  23/0000Z 29.0N  96.3W   30 KT  35 MPH - Depression (WSW Danevang, Texas)
 24H  23/1200Z 29.6N  95.1W   30 KT  35 MPH - Depression (ESE Pasadena, Texas)
 36H  24/0000Z 30.4N  93.7W   25 KT  30 MPH - Depression (WNE Lake Charles, Louisiana)
 48H  24/1200Z 31.7N  92.0W   20 KT  25 MPH - Low (WNW Jonesville, Louisiana)
 60H  25/0000Z 33.1N  90.0W   20 KT  25 MPH - Low (ESE Lexington, Mississippi)
 72H  25/1200Z 34.4N  88.3W   20 KT  25 MPH - Low (WSW Red Bay, Mississippi)
 96H  26/1200Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 1000 PM CDT Mon Sep 21, 2020 

There has been a recent increase in convection along the Texas coast just to the north of Beta’s center this evening. A blend of flight-level and SFMR winds from an Air Force Reserve reconnaissance aircraft indicate that Beta’s peak intensity remains around 40 kt. The aircraft has reported a minimum central pressure of around 999 mb, which is unchanged from earlier today. West-southwesterly vertical wind shear and land interaction should gradually weaken the cyclone over the next couple of days. The NHC intensity forecast is a little above model guidance through 24 hours since a significant portion of the circulation is forecast to remain over water. Strong vertical wind shear is expected to prevent re-strengthening when Beta moves near or just offshore of the Upper Texas coast in a couple of days.

Beta is moving northwestward or 325/3 kt. The tropical storm should move just inland along the central Texas coast overnight, but it is expected to become nearly stationary on Tuesday as steering currents collapse. A weak trough over the south-central United States should begin to steer Beta east-northeastward Tuesday night and Wednesday, and a northeastward motion at a slightly faster forward speed should continue until dissipation in 72-96 hours. The latest NHC track forecast is very similar to the previous advisory and is a blend of the latest GFS and ECMWF models.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southeast Louisiana. Flash, urban, and minor river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and east into the Lower Mississippi Valley and portions of the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds will spread westward across the Texas coast through Tuesday.
FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 28.4N  96.3W   40 KT  45 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 12H  22/1200Z 28.6N  96.3W   35 KT  40 MPH - Tropical Storm (WSW Palacios, Texas)
 24H  23/0000Z 28.8N  96.0W   35 KT  40 MPH - Tropical Storm (WSW Wadsworth, Texas)
 36H  23/1200Z 29.1N  95.0W   30 KT  35 MPH - Post Tropical (WSW Jamaica Beach, Texas)
 48H  24/0000Z 29.5N  93.8W   30 KT  35 MPH - Post Tropical (ESE Port Arthur, Texas)
 60H  24/1200Z 30.4N  92.3W   25 KT  30 MPH - Post Tropical (WSW  Church Point, Louisiana)
 72H  25/0000Z 31.7N  90.7W   20 KT  25 MPH - Low (ENE Union Church, Mississippi)
 96H  26/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Mon Sep 21, 2020 

Beta’s convective cloud structure has continued to erode since the previous advisory as cold-air stratocumulus clouds have wrapped around the entire and into the system center. Most of the cloud tops are barely reaching the freezing level, with the exception of a small convective burst that has recently developed near and to the northwest of the low-level center. The initial intensity has been lowered to 40 kt and is based on data from the last Air Force Reserve reconnaissance leg that indicated peak SFMR surface winds of 40-42 kt northwest of the center and a dropsonde-measured central pressure of 999-1000 mb.

The initial motion estimate 310/04 kt. Beta is expected to move onshore the central Texas coast later tonight, and then stalling along or just inland from the coast during the 12-24 hour period when the steering currents collapse due to a complete break down of a weak ridge over the Gulf of Mexico. A weak trough to the west of the cyclone is then forecast to nudge Beta east-northeastward toward the Gulf of Mexico in the 36-60 hour period, with the cyclone possibly reaching the warm Gulf waters by 48 hours. By 72 hours and beyond, the approaching mid-level trough Beta is expected to move Beta a little faster toward the northeast until the cyclone dissipates over the Lower Mississippi Valley area by day 5. The latest NHC track guidance has shifted a little farther to right or east of the previous forecast track, with most of the models now taking Beta back out over the western Gulf of Mexico by 24 hours. As a result, the new NHC official track forecast has been nudged a little farther to the right of the previous, but remains to the left or west of the NOAA-HCCA consensus model and the UKMET model.

West-southwesterly wind shear of 15-20 kt is expected to affect Beta for the next 36 hours or so, followed by a gradual increase in the shear thereafter. That unfavorable flow regime, along with land interaction, should induce a slow weakening trend throughout the forecast period. The NHC intensity forecast remains a little above the available model guidance through 48 hours since Beta is forecast to remain very close to or over the Gulf of Mexico where convective rain bands containing tropical-storm-force winds could possibly move onshore the central and upper Texas coastal areas.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southeast Louisiana. Flash, urban, and minor river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and east into the Lower Mississippi Valley and portions of the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds will spread westward across the Texas coast later this evening and continue into Tuesday.
FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 28.2N  96.1W   40 KT  45 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 12H  22/0600Z 28.5N  96.6W   35 KT  40 MPH - Tropical Storm (ESE Magnolia Beach, Texas)
 24H  22/1800Z 28.7N  96.5W   35 KT  40 MPH - Tropical Storm (ENE Point Comfort, Texas)
 36H  23/0600Z 28.9N  95.8W   35 KT  40 MPH - Tropical Storm (ESE Rugeley, Texas)
 48H  23/1800Z 29.2N  94.7W   30 KT  35 MPH - Post Tropical (ESE Galveston, Texas)
 60H  24/0600Z 29.7N  93.3W   25 KT  30 MPH - Post Tropical (ESE Cameron, Louisiana)
 72H  24/1800Z 30.8N  91.6W   20 KT  25 MPH - Post Tropical (ESE Lacour, Louisiana)
 96H  25/1800Z 34.1N  88.7W   20 KT  25 MPH - Post Tropical (ESE Shannon, Mississippi)
120H  26/1800Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 1000 AM CDT Mon Sep 21, 2020

There has been little change in Beta’s overall convective structure and intensity, with thunderstorm activity pulsing near the center while the outer rain bands have changed little and keep rotating onshore the central and upper Texas coastal areas. Dry air intrusions into the inner-core region have continued to prevent Beta from strengthening by eroding the central dense overcast (CDO). The initial intensity of 45 kt is based on data from an Air Force Reserve reconnaissance aircraft showing peak SFMR surface winds of 40-45 kt and maximum flight-level winds of 50 kt so far, along with a dropsonde-measured central pressure of 996-997 mb.

Beta now appears to be moving west-northwestward at a slightly faster forward speed, with the initial motion estimated to be 290/06 kt based on data from the aircraft and NOAA Doppler radars from Corpus Christi and Houston, Texas. The forecast discussion is the same old song as it was 24 hours ago with Beta expected to move just inland over the central Texas coastal Plain in about 12-18 hours, followed by a sharp decrease in motion, possibly resulting in Beta stalling for a few hours as steering currents collapse. A trough to the west combines with a broad ridge to the east located over the Gulf of Mexico to begin nudging Beta slowly northeastward or east-northeastward in 24-36 hours, followed by a slightly faster forward speed on days 3 and 4, which will continue until the cyclone dissipates over Mississippi by day 5. The new NHC track forecast is essentially just an update of the previous advisory track, keeping Beta just inland or near the Texas coast through 60 hours, a scenario that is close to the various consensus models, and which lies between the more westward-and-inland ECMWF solution and the more eastward-and-overwater GFS track forecast.

West-southwesterly vertical wind shear of 15-20 kt is not only expected to keep Beta’s track close to the coastline, but it will also affect the cyclone’s intensity along with land interaction. The closer the cyclone stays near the Gulf of Mexico, the more likely that bands of convection containing tropical-storm-force winds will continue to roll onshore the Texas coast through 36-48 hours. Given that the models over the past 24 hours have been trending toward a track closer to the coast, the NHC official intensity remains unchanged from the previous advisory, and lies a little above all of the available guidance through 48 hours.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southeast Louisiana. Flash, urban, and minor river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and east into the Lower Mississippi Valley and portions of the Southeast through the end of the week. Flash, urban, and isolated minor river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds will spread westward across the Texas coast later this morning and continue into Tuesday.
FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 27.9N  95.7W   45 KT  50 MPH - Tropical Storm (WSW Port O'Connor, Texas)
 12H  22/0000Z 28.3N  96.5W   45 KT  50 MPH - Tropical Storm (WSW Port O'Connor, Texas)
 24H  22/1200Z 28.5N  96.7W   40 KT  45 MPH - Tropical Storm (ESE Port Lavaca, Texas)
 36H  23/0000Z 28.8N  96.3W   35 KT  40 MPH - Tropical Storm (WNW Palacios, Texas)
 48H  23/1200Z 29.1N  95.3W   30 KT  35 MPH - Extra Tropical (ESE Angleton, Texas)
 60H  24/0000Z 29.7N  94.0W   25 KT  30 MPH - Extra Tropical (WSW Port Arthur, Texas)
 72H  24/1200Z 30.8N  92.5W   25 KT  30 MPH - Extra Tropical (WNW Pine Prairie, Louisiana)
 96H  25/1200Z 33.5N  89.8W   20 KT  25 MPH - Extra Tropical (WNW Winona, Mississippi)
120H  26/1200Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 1000 PM CDT Sun Sep 20, 2020 

Satellite and radar imagery shows that the deep convection associated with Beta has decreased considerably since this afternoon. This appears to be the result of dry air entrainment and vertical wind shear. Despite the recent decrease in convective organization, an Air Force Reserve Hurricane Hunter aircraft has found SFMR winds of around 45 kt, and there have been a couple of ship observations this evening of winds of 45-50 kt. Therefore, the initial intensity of 50 kt has been maintained. Data from the most recent center dropwindsonde indicate that the pressure is around 995 mb.

Beta is forecast to remain within an area of moderate vertical wind shear, and that along with intrusions of dry air are likely to prevent Beta from strengthening before it nears the Texas coast. As a result, the NHC intensity forecast shows little change in strength before landfall in about 24 hours. Gradual weakening should occur after the center moves over land, but the weakening rate may be slower-than-normal as a portion of the circulation will remain offshore. In 2-3 days, the system is expected to weaken to a tropical depression, and it should become a remnant low by 96 h as it move farther inland over the lower Mississippi Valley. The NHC intensity forecast is near the upper-end of the intensity guidance through 24 hours, and is in best agreement with the SHIPS statistical model.

Beta has jogged westward this evening, but the longer-term motion estimate is 290/5 kt. There is once again no change the previous track forecast philosophy. The tropical storm is located between a mid-level ridge over Florida and another ridge over the Southern Plains. Beta should move slowly west-northwestward toward the coast of Texas during the next 12 to 24 hours. After that time, the ridge over the Plains should weaken allowing the ridge to the east to steer Beta northward, and then northeastward near the Upper-Texas coast by mid-week. With the recent westward jog, the new track forecast has been nudged slightly south of the previous track through 24 hours, but is slightly east of the previous advisory thereafter to be closer to the various consensus aids.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and east into the Lower Mississippi Valley where flash, urban, and river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds are occurring along portions of the northwestern Gulf Coast within the tropical storm warning area in Louisiana. These winds will spread westward to the Texas coast overnight and Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 27.6N  94.5W   50 KT  60 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 12H  21/1200Z 28.0N  95.4W   50 KT  60 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 24H  22/0000Z 28.5N  96.4W   45 KT  50 MPH - Tropical Storm (WNW Port O'Connor, Texas)
 36H  22/1200Z 28.8N  96.7W   35 KT  40 MPH - Tropical Storm (ESE Inez, Texas)
 48H  23/0000Z 29.1N  96.2W   30 KT  35 MPH - Post Tropical (ENE Danevang, Texas)
 60H  23/1200Z 29.5N  95.2W   30 KT  35 MPH - Post Tropical (ESE Friendswood, Texas)
 72H  24/0000Z 30.1N  94.0W   30 KT  35 MPH - Post Tropical (ESE Vidor, Texas)
 96H  25/0000Z 31.9N  91.6W   20 KT  25 MPH - Post Tropical (ENE Sicily Island, Louisiana)
120H  26/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL  400 PM CDT Sun Sep 20, 2020 

After a short-lived intense burst of deep convection a couple of hours ago, which helped to spin up a mid-level eye feature in radar imagery, Beta’s convection has waned somewhat and the eye feature has become less distinct. Doppler velocity values of 60-65 kt between 15,000-20,000 ft were noted when the vortex column looked its best, but that spin up of the circulation also generated a significant amount of dry air entrainment that is now evident by a pronounced slot wrapping into the center from the north and northeast, which has likely caused the recent decrease in the inner-core convection.

An Air Force Reserve reconnaissance aircraft was investigating Beta during the time of the aforementioned convective burst, and the low-level center was located about 18-20 nmi east of the radar eye feature, and the surface dropsonde measured west winds of 39 kt beneath the calm 850-mb center. These data indicate that vortex column possesses a significant amount of vertical tilt, which is not suggestive of an intensifying tropical cyclone. The aircraft found that the central pressure has remained at around 996 mb and also measured an 850-mb flight-level maximum wind of 60 kt, thus the initial intensity is being held at 50 kt. After accounting for the westward jump in the low-level center due to its recent reformation, the initial motion estimate is 295/05 kt.

There is no significant change to the previous forecast track or reasoning. Beta is expected to remain within weak steering currents for the next couple of days, caught between a mid-level ridge over Florida and a weaker ridge located over the U.S. Southern Plains. Thereafter, the ridge over Florida become the dominant steering feature by amplifying northward and northwestward across the southeastern U.S. by early Tuesday, nudging Beta northward by late Tuesday, then followed by a faster northeastward motion on Wednesday through Friday. Due to the continued southwest to westerly shear expected to affect the cyclone, which will keep the convection and associated best pressure falls confined to the northeastern and eastern quadrants or near the Texas coast. As the result, the new NHC forecast track lies near the previous advisory track, and it located along the right side of the track guidance envelope, but not as far right as the new GFS-ECMWF (GFEX) consensus model. which keeps Beta over water for the next several days.

Excluding the recent weakening of the vertical wind shear, which allowed Beta to undergo that bursting phase, the cyclone is forecast to remain under the influence of 15-20 kt or greater deep-layer shear throughout the forecast period, which is strong enough to keep the cyclone from strengthening much, but not enough to weaken or dissipate the cyclone before landfall occurs in 24 hours or so. Therefore, the intensity is expected to remain steady at 50 kt until landfall, although 5-kt fluctuations could occur which are in the forecast statistical noise. Slower-than-normal weakening for an inland tropical cyclone is expected due to Beta’s proximity to the Gulf where brisk onshore flow could bring strong squalls over the Gulf into the coast. By day 3, Beta should weaken fairly quickly into a remnant low since the system will be located much farther and away from the influence of the Gulf of Mexico. The cyclone is expected to degenerate into a remnant low pressure system by early Wednesday and dissipate inland over the lower Mississippi Valley area by late Friday or Saturday. The intensity model guidance remains in good agreement on this developing forecast scenario, so no significant changes were made to the previous intensity forecast.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and river flooding is likely. Rainfall will also spread northward into the ArkLaTex region and east into the Lower Mississippi Valley where flash, urban, and river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds are occurring along portions of the northwestern Gulf Coast within the tropical storm warning area in Louisiana. These winds will spread westward to the Texas coast later today and Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 27.7N  94.0W   50 KT  60 MPH - Tropical Storm (WSW Galveston, Texas)
 12H  21/0600Z 28.1N  95.0W   50 KT  60 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 24H  21/1800Z 28.6N  96.1W   50 KT  60 MPH - Tropical Storm (WSW Matagorda, Texas)
 36H  22/0600Z 29.0N  96.7W   45 KT  50 MPH - Tropical Storm (WSW Edna, Texas)
 48H  22/1800Z 29.4N  96.4W   40 KT  45 MPH - Tropical Storm (WSW Nada, Texas)
 60H  23/0600Z 29.7N  95.7W   35 KT  40 MPH - Tropical Storm (WSW Clodine, Texas)
 72H  23/1800Z 30.0N  94.7W   30 KT  35 MPH - Post Tropical (WSW Raywood, Texas)
 96H  24/1800Z 32.0N  91.8W   20 KT  25 MPH - Post Tropical (WSW Jigger, Louisiana)
120H  25/1800Z 34.4N  89.5W   20 KT  25 MPH - Post Tropical (WNW Oxford, Mississippi)

NWS National Hurricane Center Miami FL 1000 AM CDT Sun Sep 20, 2020

Beta remains a sheared tropical cyclone whose internal structure and convective pattern remained unchanged from the previous advisory, and essentially unchanged over the past 24 hours. The cyclone is going through another bursting phase with the strongest convection displaced into the northeastern quadrant. An Air Force Reserve reconnaissance aircraft investigating Beta this morning has found maximum 850-mb flight-level winds of 61 kt in some rather vigorous thunderstorms in the north of the center, along with believable SFMR surface winds of 45-47 kt in the northeastern quadrant where 45-kt winds were reported by ship KGSG at 0800 UTC. The aircraft also found that the central pressure was down a little bit to 996 mb. Based on these data, the initial intensity is being maintained at 50 kt. It should be noted that the wind field is quite asymmetric with the strongest winds located in the deep convection and farther to the northeast behind an old frontal boundary.

Beta remains trapped in weak steering currents and the initial motion is still quite slow at 300/03 kt. Beta is forecast to remain embedded in weak steering currents for the next 48 h or so, caught between a mid-level ridge located over Florida and another ridge situated over the U.S. Southern Plains. Thereafter, the ridge over the Southern Plains if expected to break down while the ridge over Florida amplifies northward and westward across the southern U.S., resulting in a very gradual increase in forward speed toward the north by late Tuesday and then toward the northeast on Wednesday. Beta is forecast to degenerate into a remnant low pressure system by early Wednesday and dissipate inland over the lower Mississippi by late Friday or Saturday. Due to the continued southwest to westerly shear expected to affect Beta, which will keep the convection confined to the northeastern and eastern quadrants, the official forecast track is located along the eastern or right side of the track guidance envelope, and is the right of all of the consensus aids, toward the middle-to-upper Texas coast.

Beta is expected to remain under the influence of 15-20 kt of deep layer vertical wind shear, which is enough to keep the cyclone from strengthening much, if any, but not enough to weaken or dissipate the cyclone before it makes landfall. As a result, the intensity is forecast to remain steady at 50 kt until landfall, followed by slower-than-normal weakening for an inland tropical cyclone due to its expected proximity to the Gulf where onshore rainbands could brings higher squalls along the coast. By 72 h, Beta is forecast to weaken fairly quickly into a remnant low since the system will be much farther inland by that time. The intensity model guidance remain in decent agreement, so the new NHC intensity forecast is identical to the previous advisory and is similar to the HCCA consensus model.

Key Messages:

  • 1. The expected slow motion of Beta will produce a long duration rainfall event from the middle Texas coast to southern Louisiana. Flash, urban, and river flooding is likely. Rainfall will then spread northward into the lower Mississippi River Valley by mid-week where flash, urban, and river flooding is possible.
  • 2. There is the danger of life-threatening storm surge near times of high tide through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical-storm-force winds are occurring along portions of the northwestern Gulf Coast within the tropical storm warning area in Louisiana. These winds will spread westward to the Texas coast later today and Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 27.2N  93.0W   50 KT  60 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 12H  21/0000Z 27.6N  93.9W   50 KT  60 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 24H  21/1200Z 28.1N  95.0W   50 KT  60 MPH - Tropical Storm (ENE Port O'Connor, Texas)
 36H  22/0000Z 28.6N  95.8W   50 KT  60 MPH - Tropical Storm (ESE Matagorda, Texas)
 48H  22/1200Z 29.0N  96.0W   45 KT  50 MPH - Tropical Storm (WNW Bay City, Texas)
 60H  23/0000Z 29.6N  95.7W   40 KT  45 MPH - Tropical Storm (WNW Sugar Land, Texas)
 72H  23/1200Z 30.2N  94.7W   30 KT  35 MPH - Low (ENE Hardin, Texas)
 96H  24/1200Z 32.1N  92.1W   20 KT  25 MPH - Low (ESE Columbia, Louisiana)
120H  25/1200Z 34.4N  89.4W   20 KT  25 MPH - Low (ENE Oxford, Mississippi)

NWS National Hurricane Center Miami FL 1000 PM CDT Sat Sep 19, 2020

Beta’s deep convection has been waning this evening. An Air Force Reserve Hurricane Hunter aircraft has found that the central pressure rose several millibars since this morning, but the plane also still measured surface winds around 50 kt from the SFMR instrument. The strongest winds appear to be located near on old frontal boundary which extends north and east of Beta’s center, and in fact sustained tropical-storm-force winds are just grazing the coast of south-central Louisiana.

The aircraft fixes indicated that Beta drifted north-northeastward during the day. Right now, the cyclone is embedded within weak steering currents between two areas of high pressure centered near the Bahamas and west Texas/southern New Mexico. The western high pressure area is expected to slide eastward across the Southern Plains into the southeastern U.S. through Sunday night, which should force Beta to move slowly toward the west-northwest toward the Texas coast. The center is now expected to reach the coast between 48-60 hours, at which point it is likely to recurve around the mid-level high and move slowly northeastward near or inland of the upper Texas coast on days 3 and 4. Because of Beta’s drift today, the new guidance envelope has shifted a bit northward. For this forecast cycle, the NHC official forecast split the difference between the previous interpolated forecast and the HFIP Corrected Consensus guidance. This keeps the forecast to the east of the ECMWF, HCCA, and TVCN multi-model consensus during Beta’s slow recurvature.

The air mass behind the old front appears to have won out. Beta’s circulation is embedded in a dry environment of mid-level relative humidities around 50 percent, and the air mass could actually become more stable as Beta moves closer to the Texas coast. On top of that, the moderate southwesterly shear is not expected to diminish much at all. As a result, the intensity guidance has continued to trend downward, and the new official forecast now flatlines Beta’s intensity at 50 kt until landfall soon after 48 hours. This forecast still lies near the top end of the guidance envelope, closest to the SHIPS model. After 48 hours, weakening is expected assuming Beta’s center remains over land, and it is now expected to become a remnant low over Louisiana by day 5.

While the chances that Beta will become a hurricane continue to decrease, the Hurricane Watch for portions of the coast of Texas are being maintained out of an abundance of caution given the uncertainty in the forecast.

Key Messages:

  • 1. The expected slow motion of Beta has the potential to expand a long duration rainfall event from the Louisiana coast westward into southeast Texas on Sunday and northward into the Mid-South by mid next week. The potentially prolonged period of rainfall could cause flash, urban, and river flooding, especially where tide levels are above normal.
  • 2. There is the danger of life-threatening storm surge near times of high tide from Sunday through Tuesday along portions of the Texas and Louisiana coasts within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical storm force winds are expected to begin along portions of the northwestern Gulf Coast overnight within the tropical storm warning area in Louisiana and will spread westward to the Texas coast Sunday through Monday. Hurricane-force winds are possible along portions of the Texas coast late Monday and Monday night, where a hurricane watch is in effect.
FORECAST POSITIONS AND MAX WINDS

INIT  20/0300Z 26.8N  92.2W   50 KT  60 MPH - Tropical Storm (WSW Galveston, Texas)
 12H  20/1200Z 27.1N  93.0W   50 KT  60 MPH - Tropical Storm (WSW Galveston, Texas)
 24H  21/0000Z 27.4N  94.1W   50 KT  60 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 36H  21/1200Z 27.9N  95.2W   50 KT  60 MPH - Tropical Storm (ESE Port Aransas, Texas)
 48H  22/0000Z 28.4N  96.0W   50 KT  60 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 60H  22/1200Z 28.9N  96.3W   40 KT  45 MPH - Tropical Storm (WNW  Blessing, Texas)
 72H  23/0000Z 29.3N  96.0W   35 KT  40 MPH - Tropical Storm (ESE  Burr, Texas)
 96H  24/0000Z 30.2N  94.1W   30 KT  35 MPH - Post Tropical (WNW Pine Forest, Texas)
120H  25/0000Z 31.4N  92.1W   25 KT  30 MPH - Post Tropical (ENE Deville, LA)

NWS National Hurricane Center Miami FL 400 PM CDT Sat Sep 19, 2020

Satellite imagery indicates that Beta has a small area of convection over the low-level center, with a dry slot on the northeastern side separating that convection from a larger outer band. Satellite intensity estimates are generally in the 40-55 kt range and have changed little since the past advisory. In addition, a ship just north of the center just reported 47-kt winds and a pressure of 998.6 mb. Based on these data, the initial intensity remains 50 kt. Earlier scatterometer data showed a trough extending from near the center of Beta to just south of the mouth of the Mississippi River, which may be a result of the cyclone’s circulation interacting with an old cold front over the northern Gulf.

Beta has been nearly stationary since the last advisory, with the center perhaps making a small loop. The guidance is in good agreement that a slow westward to west-northwestward motion should start tonight as a mid-level ridge develops north of the cyclone. A slightly faster west-northwestward motion should then occur through 72 h, bringing the center of Beta near or over the Texas coast in about 60 h. After landfall, a mid-latitude trough moving through the central United States should cause Beta to recurve slowly to the northeast. Despite the current lack of movement, the latest track guidance is a little faster to bring the storm to the coast of Texas with the ECMWF forecasting landfall by 12Z Monday. The new forecast track is a little faster than the previous forecast, but is a little slower than the various consensus models.

There remain a lot of uncertainties in the intensity forecast. First, the global models still suggest that the ongoing southwesterly shear may not subside much before landfall. Second, GOES-16 air mass imagery shows abundant upper-level dry air over the western Gulf of Mexico, including near the storm center. Third, surface observations show a drier low-level airmass in place over southeastern Texas, and some of this may be getting entrained into the storm. The intensity guidance has again trended downward, and several of the models now forecast Beta not to strengthen at all as it approaches Texas. Because the sea surface temperatures are warm and the shear is not prohibitively strong, the intensity forecast, while reduced from the earlier forecast, will show slow strengthening to a peak intensity of 60 kt before landfall. This forecast remains above the guidance, and additional downward adjustments may be needed tonight or on Sunday.

While the chances that Beta will become a hurricane are decreasing, a Hurricane Warning could still be issued for portions of the Texas coast tonight depending on later intensity trends and forecasts.

Key Messages:

  • 1. The expected slow motion of Beta has the potential to produce a long duration rainfall event along the western Gulf Coast. The potentially prolonged period of rainfall could cause flash, urban, and river flooding, especially in coastal areas where tide levels are above normal.
  • 2. There is the danger of life-threatening storm surge near times of high tide from Sunday through Tuesday along portions of the Texas coast within the storm surge warning areas. Residents in these areas should follow advice given by local officials.
  • 3. Tropical storm force winds are expected to begin along portions of the northwestern Gulf Coast by Sunday night within the tropical storm warning area, with hurricane-force winds possible along portions of the Texas coast late Monday and Monday night, where a hurricane watch is in effect.
FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 26.6N  92.4W   50 KT  60 MPH - Tropical Storm (ESE Galveston, Texas)
 12H  20/0600Z 26.7N  93.1W   50 KT  60 MPH - Tropical Storm (ESE Galveston, Texas)
 24H  20/1800Z 27.1N  94.0W   55 KT  65 MPH - Tropical Storm (ESE Galveston, Texas)
 36H  21/0600Z 27.5N  95.1W   55 KT  65 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 48H  21/1800Z 27.9N  96.0W   60 KT  70 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 60H  22/0600Z 28.3N  96.4W   60 KT  70 MPH - Tropical Storm (ESE Port O'Connor, Texas)
 72H  22/1800Z 28.8N  96.4W   50 KT  60 MPH - Tropical Storm (ESE La Ward, Texas)
 96H  23/1800Z 29.5N  95.0W   35 KT  40 MPH - Tropical Storm (WSW Bacliff, Texas)
120H  24/1800Z 31.0N  93.0W   25 KT  30 MPH - Low (WNW  Fullerton, LA)

NWS National Hurricane Center Miami FL 1000 AM CDT Sat Sep 19, 2020 

Corrected 96 and 120 h intensities Morning visible imagery indicates that Beta has become significantly sheared, with the low-level center mostly exposed well to the southwest of the main convective area. A new convective band is currently forming near the center over the northwestern quadrant. An Air Force Reserve Hurricane Hunter aircraft reported pressures near 994-995 mb, along with flight-level and SFMR winds that justify keeping the initial intensity at 50 kt.

The storm appears to be starting its westward turn, and the initial motion is now 315/3. The mid- to upper-level trough over the northwestern Gulf of Mexico is lifting out, with a mid-level ridge building to the north of Beta. This should cause the storm to turn more westward during the next 6-12 h. After that, a slow west- northwestward to northwestward motion should develop, with the center now forecast to be near or over the middle Texas coast in about 72 h. Beyond 72 h, another mid-latitude trough moving through the central United States should cause Beta to recurve slowly to the northeast. The new NHC forecast is shifted a little to the west and now explicitly shows landfall on the Texas coast in about 72 h. This new forecast is a little to the north of the consensus models through 72 h and close to them after that time.

There are lots of uncertainties in the intensity forecast. First, the global models suggest that the ongoing southwesterly shear may not subside that much even though the first trough is lifting out. Second, GOES-16 air mass imagery shows abundant upper-level dry air over the western Gulf of Mexico, including near the storm center. Third, surface observations show a drier low-level airmass in place over southeastern Texas, and some of this may get entrained into the storm. The intensity guidance has trended downward to the point where none of the models are currently forecasting Beta to become a hurricane. Based on this and the current storm structure, the intensity forecast has been adjusted to show little change in strength today, followed by slow strengthening to a hurricane by 48-60 h. However, this forecast is well above the guidance, and additional downward adjustments may be needed later today.

A Tropical Storm Warning is being issued for parts of the Texas and Louisiana coasts at this time. A Hurricane Warning could still be issued later today or tonight depending on later intensity forecasts.

Key Messages:

  • 1. The expected slow motion of Beta has the potential to produce a long duration rainfall event along the western Gulf Coast. The potentially prolonged period of rainfall could cause flash, urban, and river flooding, especially where tide levels are above normal.
  • 2. Life-threatening storm surge and hurricane-force winds are possible along portions of the northwestern Gulf Coast, with tropical storm conditions expected by late this weekend. Storm Surge and Hurricane watches and Tropical Storm warnings are in effect, and residents in these areas should ensure they have their hurricane plan in place and follow advice given by local officials.
FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 26.6N  92.6W   50 KT  60 MPH - Tropical Storm (ENE South Padre Island, Texas)
 12H  20/0000Z 26.9N  93.0W   50 KT  60 MPH - Tropical Storm (ENE South Padre Island, Texas)
 24H  20/1200Z 27.1N  93.8W   55 KT  65 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 36H  21/0000Z 27.5N  94.8W   60 KT  70 MPH - Tropical Storm (ESE Corpus Christi, Texas)
 48H  21/1200Z 27.8N  95.5W   65 KT  75 MPH - Category 1 (ENE Corpus Christi, Texas)
 60H  22/0000Z 28.2N  96.2W   65 KT  75 MPH - Category 1 (ESE Port O'Connor, Texas)
 72H  22/1200Z 28.6N  96.2W   55 KT  65 MPH - Tropical Storm (WSW Matagorda, Texas)
 96H  23/1200Z 29.5N  95.0W   45 KT  50 MPH - Tropical Storm (WSW Bacliff, Texas)
120H  24/1200Z 30.5N  93.0W   30 KT  35 MPH - Tropical Storm (ESE Reeves, LA)

NWS National Hurricane Center Miami FL 1000 PM CDT Fri Sep 18, 2020 

An Air Force Reserve Hurricane Hunter aircraft investigating Beta this evening found that the center has re-formed or been tugged northeastward by bursts of strong convection. While flying through that convection, the plane measured a peak flight-level wind of 57 kt at 10,000 feet before descending to 2500 feet. To the northwest of the center, the SFMR instrument on the plane measured a solid area of 46-48 kt, and there have been multiple ship reports in the region of 40-45 kt. Based on all these data, Beta’s initial intensity is estimated to be 50 kt. The plane reported an extrapolated minimum pressure of 996 mb on the last pass through the center, which also corresponds to a typical 50-kt tropical storm.

The aircraft fixes indicate that Beta is moving north-northeastward, or 030/10 kt. This motion is expected to continue for the next 12 hours or so, but as mid-level ridging develops over the Southern Plains on Saturday, Beta should begin to slow down and turn westward. A slow motion in the direction of the Texas coast should continue through day 3, with a shortwave trough possibly causing the cyclone to recurve and move northeastward near or along the Texas coast on days 4 and 5. While there remains a large amount of spread among the track models, they all agree on this general scenario and indicate that Beta is likely to move very slowly as it makes its closest approach to the Texas coast. The initial position fixed by the plane necessitated a northward shift in the NHC official forecast compared to the previous forecast for the first 3 days, but it comes back in line with the previous prediction on days 4 and 5.

Beta has been able to strengthen despite being affected by strong southwesterly shear. The shear could begin to relax over the next few days, particularly by day 2 and 3, which could allow for some further strengthening. The SHIPS guidance remains the most aggressive of the intensity models, and the NHC intensity forecast leans heavily toward those solutions given Beta’s recent intensification trend (which SHIPS seemed to handle better). Beta is forecast to steadily strengthen and become a hurricane in a couple of days as it approaches the Texas coast. Some weakening is forecast on days 4 and 5 due to another increase in southwesterly shear and possible land interaction.

Key Messages:

  • 1. There is an increasing risk of heavy rainfall and flooding along the northwest Gulf Coast Sunday through at least the middle of next week as Beta is forecast to move slowly toward and along or offshore of the coast through that time. For additional information, see products from your local National Weather Service office.
  • 2. Life-threatening storm surge and hurricane-force winds are possible along portions of the Texas coast early next week, with tropical storm conditions possible by late this weekend. Storm Surge and Hurricane watches are in effect, and residents in these areas should ensure they have their hurricane plan in place and follow advice given by local officials.
FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 25.5N  92.3W   50 KT  60 MPH - Tropical Storm (ENE El Mezquital, Mexico)
 12H  19/1200Z 26.3N  92.2W   55 KT  65 MPH - Tropical Storm (ESE South Padre Island, Texas)
 24H  20/0000Z 26.8N  92.8W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 36H  20/1200Z 26.8N  93.7W   65 KT  75 MPH - Category 1 (ESE Padre Island, Texas)
 48H  21/0000Z 27.0N  94.6W   70 KT  80 MPH - Category 1 (ESE Padre Island, Texas)
 60H  21/1200Z 27.4N  95.5W   70 KT  80 MPH - Category 1 (ESE Padre Island, Texas)
 72H  22/0000Z 27.8N  96.0W   70 KT  80 MPH - Category 1 (ESE San Jose Island, Texas)
 96H  23/0000Z 28.4N  95.8W   65 KT  75 MPH - Category 1 (ESE Matagorda, Texas)
120H  24/0000Z 29.4N  94.1W   55 KT  65 MPH - Tropical Storm (ENE Galveston, Texas)

NWS National Hurricane Center Miami FL 400 PM CDT Fri Sep 18, 2020 

Satellite imagery indicates that the circulation of Tropical Depression 22 has become better defined, and most objective and subjective satellite intensity estimates are now 35 kt. Based on this, along with 33 kt 1-mi average winds from NOAA buoy 42002, the depression is upgraded to Tropical Storm Beta with an initial intensity of 35 kt. Although the system is now a tropical storm, satellite imagery shows that the convective pattern is becoming elongated due to the effects of southwesterly vertical wind shear.

Visible imagery and scatterometer data showed that the center of Beta was a bit farther east than previously thought, and the initial motion is a somewhat uncertain 025/8. This motion should continue for the next 12-24 h as the storm is steered by a mid- to upper-level trough over Texas and northeastern Mexico. After that time, the trough should weaken and lift out to the northeast, with a mid-level ridge building to the north of the cyclone above an already present low-level ridge. This ridge should act as a Beta blocker, causing the storm to turn westward toward the western Gulf coast.

Between 72-120 h, the mid-level ridge weakens as another mid-latitude trough moves through the central United States, and this is expected to cause the storm to slowly recurve toward the northeast. One change in the track guidance since the previous forecast is that the GFS and ECMWF are a bit faster on the westward motion and show the center near the Texas coast in about 72 h. The latter part of the new track forecast also shifts westward, but it is still to the east of the GFS/ECMWF. There is also a chance that Beta could move more northward than forecast before the trough lifts out, which adds an additional touch of uncertainty to the track forecast. So, it is critical that users not focus on the exact forecast track, especially at days 3 to 5.

The global models suggest that the current shear may decrease a little after 24 h when the upper-level trough moves away from Beta. However, there is a chance of at least some dry air entrainment that would hamper strengthening. The intensity guidance for the most part continues to forecast Beta to reach a peak intensity below hurricane strength, although the latest SHIPS model forecasts a peak intensity near 65 kt. The new intensity forecast is again unchanged in making Beta a hurricane at 60 and 72 h, and it lies at the upper edge of the intensity guidance.

Key Messages:

  • 1. Beta is expected to strengthen and possibly become a hurricane, while moving slowly over the western Gulf of Mexico during the next few days.
  • 2. There is an increasing risk of heavy rainfall and flooding along the northwest Gulf Coast Sunday through at least the middle of next week as Beta is forecast to move slowly toward and along or offshore of the coast through that time. For additional information, see products from your local National Weather Service office.
  • 3. While it is too early to determine what areas could see direct wind and storm surge impacts from Beta, interests throughout the western Gulf of Mexico should monitor the progress of this system and future updates to the forecast. Storm Surge and Tropical Storm or Hurricane watches could be issued tonight or Saturday.
FORECAST POSITIONS AND MAX WINDS

INIT  18/2100Z 24.3N  93.1W   35 KT  40 MPH - Tropical Storm (ENE La Pesca, Mexico)
 12H  19/0600Z 25.1N  92.9W   40 KT  45 MPH - Tropical Storm (ENE El Mezquital, Mexico)
 24H  19/1800Z 25.9N  93.0W   45 KT  50 MPH - Tropical Storm (ESE South Padre Island, Texas)
 36H  20/0600Z 26.1N  93.7W   50 KT  60 MPH - Tropical Storm (ESE South Padre Island, Texas)
 48H  20/1800Z 26.3N  94.6W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 60H  21/0600Z 26.5N  95.5W   65 KT  75 MPH - Category 1 (ESE Padre Island, Texas)
 72H  21/1800Z 26.8N  96.3W   65 KT  75 MPH - Category 1 (ESE Padre Island, Texas)
 96H  22/1800Z 27.5N  96.5W   60 KT  70 MPH - Tropical Storm (ESE Port Aransas, Texas)
120H  23/1800Z 28.5N  96.0W   55 KT  65 MPH - Tropical Storm (ENE Port O'Connor, Texas)

NWS National Hurricane Center Miami FL 1000 AM CDT Fri Sep 18, 2020

Satellite imagery indicates that Tropical Depression Twenty-Two is getting better organized, with gradually increasing convective banding in the northeastern semicircle. Satellite intensity estimates include 35 kt from TAFB, 30 kt from SAB, and 35 kt from CIMSS satellite consensus, which means the depression is close to tropical-storm strength. Given the lack of organization seen in earlier scatterometer data, the intensity will be held at 30 kt pending the data from the next set of scatterometer overpasses.

It should be noted that the Air Force Reserve Hurricane Hunter aircraft that was scheduled to investigate the depression had to turn back after getting hit by lightning. The initial motion is a somewhat uncertain 015/6. For the next 24 h or so, the cyclone should move north-northeastward as it is steered by a mid- to upper-level trough over Texas and northeastern Mexico. This trough is then expected to lift out to the northeast, with low- to mid-level ridging building to the north of the cyclone. This should cause a westward turn at a continued slow forward speed. Near the end of the forecast period, a mid-latitude trough over the central United States should cause the ridge to weaken and steer the cyclone northward to northeastward near the Texas coast.

While the guidance agrees with this general sense of the motion, there are a lot of differences in the models on the when’s and where’s of the various turns. Therefore, it is critical that users not focus on the exact forecast track, especially at days 4 and 5 when the average NHC forecast error is about 175 and 200 miles, respectively. The depression is currently in an environment of light to moderate southwesterly shear, and the global models suggest that this will generally continue through the forecast period. This, combined with forecast dry air entrainment near the 72 h point, has resulted in the intensity guidance keeping the system near to below hurricane strength through the forecast period. The new intensity forecast is changed little from the previous one and calls for the cyclone to be at hurricane strength at 60 and 72 h. However, this part of the forecast lies at the upper edge of the intensity guidance envelope.

Key Messages:

  • 1. Tropical Depression Twenty-Two is expected to strengthen to a tropical storm, and possibly a hurricane, while moving slowly over the western Gulf of Mexico during the next few days.
  • 2. There is an increasing risk of heavy rainfall and flooding along the Texas coast from Sunday through at least the middle of next week as the system is forecast to move slowly near the Texas coast. For additional information, see products from your local National Weather Service office.
  • 3. While it is too early to determine what areas could see direct wind and storm surge impacts from this system, interests throughout the western Gulf of Mexico should monitor the progress of this system and future updates to the forecast.
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1500Z 23.8N  93.9W   30 KT  35 MPH - Depression (ENE La Pesca, Mexico)
 12H  19/0000Z 24.8N  93.6W   35 KT  40 MPH - Tropical Storm (ENE El Mezquital, Mexico)
 24H  19/1200Z 25.9N  93.4W   45 KT  50 MPH - Tropical Storm (ESE South Padre Island, Texas)
 36H  20/0000Z 26.3N  93.8W   50 KT  60 MPH - Tropical Storm (ESE South Padre Island, Texas)
 48H  20/1200Z 26.5N  94.6W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 60H  21/0000Z 26.6N  95.6W   65 KT  75 MPH - Category 1 (ESE Padre Island, Texas)
 72H  21/1200Z 26.9N  96.2W   65 KT  75 MPH - Category 1 (ESE Padre Island, Texas)
 96H  22/1200Z 27.5N  96.5W   60 KT  70 MPH - Tropical Storm (ENE Padre Ismand, Texas)
120H  23/1200Z 28.5N  95.5W   55 KT  65 MPH - Tropical Storm (ENE Padre Ismand, Texas)

NWS National Hurricane Center Miami FL 1000 PM CDT Thu Sep 17, 2020

Inspection of flight-level wind data from the earlier Air Force Reserve mission indicates that the depression has a somewhat elongated circulation, but a sufficiently well-defined center and pressure minimum were found just to the west of NOAA buoy 42055. The plane measured maximum surface winds of 30 kt in the deep convection to the southwest of the center using the SFMR instrument, and that remains the initial intensity.

As best as I can tell, the depression is moving very slowly northeastward with an initial motion of 035/3 kt. A positively tilted mid- to upper-level trough extends across Texas and northern Mexico, and this feature should cause the depression to move toward the north-northeast during the next 36 hours. The trough is expected to dissolve soon after that time, with a mid-tropospheric high building over the south-central United States. The high should force the cyclone to turn and move very slowly westward on days 3 and 4, and then potentially stall or meander off the lower Texas/ northeastern Mexico coast by day 5. There is lower-than-normal confidence in the official track forecast due to fairly significant spread among the track guidance. However, the models do agree on the general scenario, and they all suggest that the depression is unlikely to move a whole lot for the entire forecast period. This new NHC forecast lies very close to the TVCN multi-model consensus.

Unfortunately, there is also significant uncertainty in the intensity forecast. Light-to-moderate southerly to southwesterly shear is expected to affect the depression for the next couple of days while it moves over very warm waters of 30-31 degrees Celsius and in a very moist environment. Things change quickly after 48 hours due to a cold front entering the northern Gulf, and the drier, more stable air mass behind the front could be entrained into the cyclone’s circulation from day 3 to day 5. The GFS- and ECMWF-based SHIPS models show the most significant strengthening, bringing the intensity to 75-80 kt in about 3 days, while many of the other intensity models don’t even raise it to hurricane intensity. As a compromise between these various solutions, the NHC intensity forecast shows the cyclone just reaching the hurricane threshold in 2-3 days and then gradually weakening thereafter due to the less favorable environment. However, it cannot be stressed enough that this forecast is highly uncertain.

Key Messages:

  • 1. Tropical Depression Twenty-Two is expected to strengthen to a tropical storm, and possibly a hurricane, while moving slowly over the western Gulf of Mexico during the next few days.
  • 2. While it is too early to determine what areas could see direct wind, storm surge, and rainfall impacts from this system, interests throughout the western Gulf of Mexico should monitor the progress of this system and future updates to the forecast.
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/0300Z 22.0N  94.2W   30 KT  35 MPH - Depression (ENE Tampico, Mexico)
 12H  18/1200Z 22.9N  93.8W   35 KT  40 MPH - Tropical Storm (ENE La Pesca, Mexico)
 24H  19/0000Z 23.9N  93.3W   45 KT  50 MPH - Tropical Storm (ENE La Pesca, Mexico)
 36H  19/1200Z 24.8N  92.9W   55 KT  65 MPH - Tropical Storm (ESE South Padre Island, Texas)
 48H  20/0000Z 25.4N  93.2W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 60H  20/1200Z 25.6N  94.0W   65 KT  75 MPH - Category 1 (ESE South Padre Island, Texas)
 72H  21/0000Z 25.7N  94.8W   65 KT  75 MPH - Category 1 (ESE South Padre Island, Texas)
 96H  22/0000Z 26.1N  95.9W   60 KT  70 MPH - Tropical Storm (ESE Padre Island, Texas)
120H  23/0000Z 26.4N  96.0W   55 KT  65 MPH - Tropical Storm (ESE Padre Island, Texas)

NWS National Hurricane Center Miami FL 600 PM CDT Thu Sep 17 2020

Reports from an Air Force Reserve Hurricane Hunter aircraft indicate that the low-pressure area over the southwestern Gulf of Mexico has developed a sufficiently well-defined circulation, with SFMR wind data suggesting an intensity of about 30 kt. In addition, the associated convection is organized enough for SAB and TAFB to provide Dvorak satellite intensity estimates of 30 kt. Based on this information, advisories are being initiated on Tropical Depression Twenty-Two.

The initial motion is a somewhat uncertain 035/4. During the next 48 h or so, the cyclone should be steered slowly north-northeastward by a mid- to upper-level trough over Texas and northern Mexico. After that time, the global models are in good agreement that this trough will weaken and lift out to the northeast, with a weak mid-level ridge building to the north of the cyclone. This should result in a gradual turn toward the west at a continued slow forward speed. Although the cyclone is relatively close to land, the vast majority of the track guidance keeps the system offshore for the next five days. The official forecast will follow this scenario, with the forecast track being between the HCCA corrected consensus and the other consensus models.

The large-scale models suggest that the cyclone will be in an environment of light to moderate vertical wind shear for the next several days. Some dry air entrainment may occur after 48 h. The bulk of the intensity guidance keeps the system below hurricane strength during the forecast period. The official intensity forecast follows the trend of the guidance and shows the system peaking as a tropical storm, but it lies a little above the intensity consensus.

As mentioned above, the cyclone is likely to stay offshore during the forecast period. Therefore, it is too early to tell which parts of the coast of the Gulf of Mexico will get wind, storm surge, and rain impacts from this system

Key Messages:

  • 1. The system is expected to strengthen to a tropical storm while moving slowly over the western Gulf of Mexico during the next few days.
  • 2. While it is too early to determine what areas could see direct wind, storm surge, and rainfall impacts from this system, interests throughout the western Gulf of Mexico should monitor the progress of this system and future updates to the forecast.
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/2300Z 21.9N  94.3W   30 KT  35 MPH - Depression (ESE Tampico, Mexico)
 12H  18/0600Z 22.7N  94.0W   30 KT  35 MPH - Depression (ENE Tampico, Mexico)
 24H  18/1800Z 23.8N  93.5W   35 KT  40 MPH - Tropical Storm (ENE La Pesca, Mexico)
 36H  19/0600Z 24.8N  93.0W   45 KT  50 MPH - Tropical Storm (ENE El Mezquital, Mexico)
 48H  19/1800Z 25.4N  92.9W   55 KT  65 MPH - Tropical Storm (ESE South Padre Island, Texas)
 60H  20/0600Z 25.8N  93.1W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 72H  20/1800Z 26.1N  93.8W   60 KT  70 MPH - Tropical Storm (ESE South Padre Island, Texas)
 96H  21/1800Z 26.1N  95.1W   55 KT  65 MPH - Tropical Storm (ESE Padre Island, Texas)
120H  22/1800Z 25.6N  96.1W   50 KT  60 MPH - Tropical Storm (ESE Padre Island, Texas)

If this system is named, it will become Tropical Storm Beta.

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Video: 5:30 PM UPDATE: Houston area bracing for return of Beta’s rain