Tropical Storm Pamela

Post Tropical Storm Pamela Track 2200 Hours Ocober 13 2021
Post Tropical Storm Pamela Track 2200 Hours Ocober 13 2021

Tropical Storm Pamela Wind Speed FieldTropical Storm PamelaNWS National Hurricane Center Miami FL 1000 PM CDT Wed Oct 13, 2021 (see NEW Wednesday video below)

Satellite imagery and surface observations indicate that Pamela has dissipated over the mountainous terrain of northern Mexico.

Therefore, this will be the final NHC advisory on Pamela.

Although the system has dissipated, deep-layer moisture associated with Pamela’s remnants will continue to spread over the south-central United States. As a result, heavy rainfall is expected across portions of central Texas and southeastern Oklahoma through Thursday. These rains may contribute to considerable flash and urban flooding impacts. For additional information on the heavy rainfall and flood potential, please consult products issued by your local National Weather Service forecast office.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 27.5N 101.5W   25 KT  30 MPH - Post Tropical (WSW Alameda,MX)
 12H  14/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Wed Oct 13, 2021 

As Pamela has moved further inland over the high, rugged terrain of west-central Mexico, its satellite structure has deteriorated markedly. Inland surface observations also suggest that the system’s low-level circulation is becoming ill-defined. Following the typical rapid rate of decay of tropical cyclones over this portion of Mexico, the maximum sustained winds are quickly lowering, now estimated at 30 kt this advisory, making Pamela a tropical depression.

The estimated motion continues to accelerate, now at 045/24 kt. This motion and heading should continue until the system dissipates over the higher terrain of Central Mexico this evening. A 12 hour point in this forecast has been provided for continuity purposes though the surface center will likely dissipate beforehand. This track also represents where the remnant mid-level vorticity maximum of Pamela will continue to propagate northeastward. This feature is also associated with a deep-layer moisture plume that is expected to contribute to heavy rainfall and flooding impacts over the south-central United States.

Key Messages:

  • 1. Heavy rains and the threat of flash flooding associated with Pamela will be diminishing through tonight over Mexico.
  • 2. Heavy rains associated with the remnants of Pamela are expected across portions of central Texas and southeastern Oklahoma through Thursday. This may result in considerable flash and urban flooding impacts.
FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 26.0N 103.7W   30 KT  35 MPH - Depression (ESE Jaboncillo,MX)
 12H  14/0600Z 28.6N 100.4W   25 KT  30 MPH - Post Tropical (ESE Rosita South,TX)
 24H  14/1800Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 900 AM MDT Wed Oct 13, 2021 

Pamela is estimated to have made landfall around 1200 UTC close to Estacion Dimas in the Mexican state of Sinaloa as a 65-kt hurricane. To the southeast of the landfall location, observations from the Mazatlan Airport indicated wind gusts to 40 kt had occurred. There was also a storm chaser located at Marmor de Salcido, Mexico, who measured a minimum pressure of 990.8 mb with southeasterly winds to 20 kt at 1208 UTC. Thus, based on these data, the estimated landfall location and an estimated minimum central pressure of 987 mb appears reasonable. Vigorous deep convection is still occuring around Pamela’s estimated center as it moves farther inland. However, since the center has been onshore for a few hours now, the wind field is likely starting to spin down and maximum sustained winds are estimated to have decreased to 55 kt.

The tropical cyclone has been accelerating to the northeast this morning, with the latest estimated motion at 045/20 kt. Further acceleration to the northeast is expected as the system remains embedded in deep-layer southwesterly flow between a long-wave trough over the western United States and a mid-level ridge centered over the Gulf of Mexico. The track guidance is in good agreement on this solution with the storm losing its identity after the 12-h forecast period and the latest track forecast remains close to the model consensus solutions.

Pamela’s circulation is not forecast to survive the passage over the high, rugged terrain of Central Mexico, but its remnants are expected to contain a large slug of deep-layer moisture that will be advected northeastward into the south-central United States. Additional heavy rainfall and flooding impacts are anticipated later today and on Thursday for these areas.

Key Messages:

  • 1. Although Pamela is moving inland into west-central Mexico this morning, a Tropical Storm warning remains in effect from Bahia Tempehuaya to Escuinapa where tropical storm conditions are still expected for the next several hours. Residents in this area should follow any advice given by local officials.
  • 2. Heavy rains associated with Pamela will continue across the Mexican States of Sinaloa, western Durgano, and northern Nayarit through today. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 3. Heavy rains associated with the remnants of Pamela are expected across portions of central Texas and southeastern Oklahoma today into Thursday. This may result in considerable flash and urban flooding impacts.
FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 24.4N 106.0W   55 KT  65 MPH - Tropical Storm (WSW Las Delicias,MX)
 12H  14/0000Z 26.6N 102.7W   30 KT  35 MPH - Depression (ESE El Venado,MX)
 24H  14/1200Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 900 PM MDT Tue Oct 12, 2021

Westerly shear has continued to prevent Pamela from restrengthening this evening. Although there was a significant burst of deep convection since the previous advisory, the center remains on the northwestern edge of the convective cloud mass and more recently the cloud tops associated with that burst has begun to warm. A blend of subjective Dvorak T- and CI-numbers from SAB and TAFB, and the latest UW-CIMSS SATCON estimate stills support an initial intensity of 60 kt. Another Air Force Reserve reconnaissance aircraft is scheduled to investigate Pamela overnight, which should provide a better assessment of the cyclone’s intensity.

Recent center fixes show that Pamela has made its much anticipated north-northeastward turn, and it is now moving 020/10 kt. The tropical storm should accelerate northeastward during the next 12 to 24 hours as it gets caught in deep-layer southwesterly flow between a mid-level ridge over the western Gulf of Mexico, and an approaching mid-latitude trough to the northwest. This motion should bring the center of Pamela to the coast of west-central mainland Mexico around 1200 UTC Wednesday morning. After that time, Pamela or its remnants should continue moving quickly northeastward across central and northern Mexico through Wednesday night. Although a 36-h post-tropical cyclone point is shown over southern Texas, the low-level center is likely to dissipate over the mountainous terrain of Mexico late Wednesday or Wednesday night.

Pamela will be moving over very warm SSTs of around 31C overnight, and that combined with a slightly more conducive upper-level wind pattern should allow Pamela to restrengthen into a hurricane before it reaches the coast of Mexico Wednesday morning. After landfall, rapid weakening will occur as Pamela moves over the rugged terrain of west-central Mexico. The latest NHC intensity forecast is again near the higher side of the guidance envelope, but it shows a slightly lower peak intensity before landfall than the previous official forecast.

Although Pamela is likely to dissipate over the rugged terrain of Mexico, deep moisture associated with the system’s remnants are likely to spread over north-central and northeastern Mexico on Wednesday, and then move into portions of the south-central United States late Wednesday or Thursday.

Key Messages:

  • 1. Pamela is forecast to restrengthen into a hurricane before it reaches the west-central coast of Mexico on Wednesday morning, and life-threatening storm surge and dangerous hurricane-force winds are expected within the Hurricane Warning area. Residents in this area should follow any advice given by local officials.
  • 2. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durango along with southern portions of Baja California Sur tonight and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 3. Heavy rains associated with the remnants of Pamela are expected across portions of central Texas and southeastern Oklahoma late Wednesday and Thursday. This may result in considerable flash and urban flooding impacts.
FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 21.9N 108.7W   60 KT  70 MPH - Tropical Storm (WNW Puerto Vallarta,MX)
 12H  13/1200Z 23.8N 106.9W   70 KT  80 MPH - Category 1 (WSW Mazatlán,MX)
 24H  14/0000Z 26.6N 103.3W   30 KT  35 MPH - Depression (ENE Las Morenas,MX)
 36H  14/1200Z 29.7N  99.7W   20 KT  25 MPH - Post Tropical (ENE Concan,TX)
 48H  15/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 300 PM MDT Tue Oct 12, 2021 

Entrainment of very dry mid-level air from the west and northwest appears to have eroded Pamela’s deep convection in the northwestern semicircle, leaving the low-level center partially exposed again similar to this time yesterday. Although there could still be some upper-level wind shear affecting the cyclone, dropsonde wind data from an earlier Air Force Reserve reconnaissance aircraft indicate that the vortex column from the surface to at least the 700-mb level was vertically aligned with no tilt evident. The highest aircraft flight-level and SFMR winds only support an intensity of about 55 kt. However, the aircraft measured a central pressure of 989 mb on its second and outbound pass through the center, which was a decrease of 2 mb from the first pass, and would support an intensity close to hurricane strength. Based on the relatively low central pressure, and the possibility that stronger winds might exist east of the center in an area that wasn’t sampled by the aircraft, Pamela’s intensity has only been lowered to 60 kt for this advisory. Data from the aircraft indicated that the 34-kt wind radii had expanded in all quadrants despite Pamela’s peak winds having weakened. Another Air Force Reserve reconnaissance aircraft is scheduled to investigate Pamela later tonight around 0530 UTC.

The initial motion estimate is northward, or 360/08 kt. Now that Pamela is on or just north of the axis of a deep-layer ridge, a sharp turn toward the north-northeast should occur very soon, followed by a northeastward motion tonight as the cyclone becomes embedded within southwesterly flow ahead of a broad mid- to upper-level trough. Pamela should then accelerate toward the west-central coast of Mexico tonight through Wednesday due to the deep-layer steering flow on the southeast side of the aforementioned trough. Landfall is still expected to occur along the west-central coast of Mexico a little before 1200 UTC Wednesday morning. After the hurricane moves inland, Pamela, or its remnants will continue to accelerate northeastward across central and northern Mexico, and move into Texas by Thursday night. The new NHC track model guidance remains tightly packed around the previous advisory track, so no significant changes were required.

It might not seem like it based on the downward satellite trends today, but the negative effects from modest vertical shear and dry air that have been affecting the cyclone will gradually subside once Pamela makes the expected northeastward turn later this evening. During that same time, the deep-layer shear vector is forecast to slowly back around to a southwesterly direction and become aligned with the hurricane’s forward motion, which will help to reduce some of the effects of the shear. Surrounding dry mid-level air could still be a hindering factor, but this negative parameter is expected to be offset by Pamela moving over very warm sea-surface temperatures of almost 31 deg C overnight. The higher ocean heat content should increase the available instability during the normal convective maximum period tonight, enabling the cyclone to restrengthen to hurricane status, and continue to strengthen right up until landfall occurs. Although it now appears unlikely that the cyclone will become a major hurricane, Pamela could still become a category 2 hurricane prior to landfall. After landfall occurs, rapid decay due to interaction with the mountainous terrain of Mexico is expected, with the cyclone ultimately dissipating over northern Mexico in a couple of days. The latest NHC intensity forecast lies near or above the upper end of the intensity guidance.

Although the cyclone is forecast to dissipate over the rugged terrain of Mexico, deep moisture associated with the system’s remnants are likely to spread over north-central and northeastern Mexico on Wednesday, and then move into portions of the south-central United States late Wednesday or Thursday.

Key Messages:

  • 1. Pamela is forecast to restrengthen into a hurricane before it reaches the west-central coast of Mexico on Wednesday morning, and life-threatening storm surge and dangerous hurricane-force winds are expected within the Hurricane Warning area. Residents in this area should follow any advice given by local officials.
  • 2. Pamela is expected to pass south of the southern tip of the Baja California peninsula as a hurricane this afternoon and tonight, and tropical-storm conditions are possible within the Tropical Storm Watch area, primarily in strong gusts.
  • 3. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durgano along with southern portions of Baja California Sur Tuesday and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 4. Heavy rains associated with the remnants of Pamela are expected across portions of central Texas and southeastern Oklahoma late Wednesday and Thursday. This may result in considerable flash and urban flooding impacts.
FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 21.0N 109.3W   60 KT  70 MPH - Tropical Storm (WNW Puerto Vallarta,MX)
 12H  13/0600Z 22.7N 107.9W   75 KT  85 MPH - Category 1 (WSW Mazatlán,MX)
 24H  13/1800Z 25.4N 105.2W   35 KT  40 MPH - Tropical Storm (WNW Vargas,MX)
 36H  14/0600Z 28.8N 101.3W   25 KT  30 MPH - Post Tropical (WSW El Cedro,MX)
 48H  14/1800Z 32.0N  97.8W   25 KT  30 MPH - Post Tropical (WSW Hillsboro,TX)
 60H  15/0600Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 900 AM MDT Tue Oct 12, 2021

Similar to this time yesterday, Pamela is undergoing an episodic convective bursting phase. The convection is likely being modulated by west-northwesterly mid-level shear of at least 15 kt that is undercutting the outflow layer, plus intrusions of dry mid-level air with humidity values near 55 percent, as analyzed in SHIPS diagnostics. The intensity at 1200 UTC was increased to 70 kt based on an average of subjective Dvorak satellite classifications of T4.5/77 kt from TAFB and T4.0/65 kt from SAB, and an objective estimate of 70 kt from UW-CIMSS ADT. An Air Force Reserve reconnaissance aircraft is currently en route to investigate Pamela’s structure, intensity, and wind field.

Pamela is moving northward or 010/11 kt. The hurricane is now on or just north of the east-west-oriented axis of a deep-layer subtropical ridge situated over central Mexico. The northward motion should continue this morning, followed by a turn toward the northeast by this afternoon or early evening as Pamela becomes embedded within southwesterly environmental flow ahead of a broad mid-/upper-level trough. That large-scale feature will cause the hurricane to accelerate tonight through Wednesday, with Pamela now expected to reach the coast of west-central Mexico just before 1200 UTC Wednesday morning. After the hurricane moves inland early Wednesday, Pamela, or its remnants should continue to accelerate northeastward across central and northern Mexico and into Texas by the end of the week. The latest NHC model guidance is tightly packed around the previous advisory forecast track, so no significant changes were required.

The latest GFS- and ECMWF-based SHIPS intensity models output show that west-northwesterly 850-200-mb shear of at least 15 kt is allegedly affecting Pamela. However, shear analyses from UW-CIMSS indicate that the shear is less than 10 kt from the west. Once Pamela makes the northeastward turn, the deep-layer shear vector is forecast to back around to a southwesterly direction and become aligned with the hurricane’s forward motion, which should help to lessen the negative effects of the vertical wind shear. Although the mid-level moisture is expected to be somewhat austere at only 50-55 percent, Pamela will be moving over sea-surface temperatures (SST) near 31 deg C, which is almost 1 deg C warmer than current SST values beneath the hurricane. This expected increase in ocean heat content, along with decreasing shear, should enhance the convective bursting phase that Pamela will likely undergo later tonight during the nocturnal convective maximum period, enabling the cyclone to strengthen to near major hurricane status before landfall occurs. The new NHC intensity forecast continues to indicate steady to rapid strengthening, and remains above all of the available intensity guidance. After landfall, Pamela is expected to rapidly decay due to interaction with the mountainous terrain of Mexico, with the cyclone ultimately dissipating over northern Mexico in 2 to 3 days. Another aircraft reconnaissance mission to investigate Pamela is scheduled for tonight at 0530 UTC.

Although the cyclone is forecast to dissipate over the rugged terrain of Mexico, deep moisture associated with the system’s remnants are likely to spread over north-central and northeastern Mexico on Wednesday, and then move into portions of the south-central United States late Wednesday or Thursday.

Key Messages:

  • 1. Pamela is forecast to be near major hurricane intensity when it reaches the west-central coast of Mexico on Wednesday morning, and life-threatening storm surge and dangerous hurricane-force winds are expected within the Hurricane Warning area. Residents in this area should follow any advice given by local officials.
  • 2. Pamela is expected to pass south of the southern tip of the Baja California peninsula as a hurricane later today and tonight, and tropical-storm conditions are possible within the Tropical Storm Watch area.
  • 3. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durgano along with southern portions of Baja California Sur Tuesday and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 4. Heavy rains associated with Pamela are expected across portions of central Texas and southeastern Oklahoma late Wednesday and Thursday. This may result in flash and urban flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 20.4N 108.9W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta,MX)
 12H  13/0000Z 21.8N 108.3W   85 KT 100 MPH - Category 2 (WNW Puerto Vallarta,MX)
 24H  13/1200Z 24.1N 106.4W   65 KT  75 MPH - Category 1 (WSW Mazatlán,MX)
 36H  14/0000Z 27.1N 103.3W   30 KT  35 MPH - Depression (WSW Los Americanos,MX)
 48H  14/1200Z 30.7N  99.0W   25 KT  30 MPH - Post Tropical (WNW Castell,TX)
 60H  15/0000Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 900 PM MDT Mon Oct 11, 2021 

Pamela continues to be affected by some modest northwesterly mid-level shear that has caused the low-level center to be located near the northwestern edge of the deep convection. This was evident in an earlier AMSR2 microwave image that arrived shortly after the release of the previous NHC advisory package. Recent objective and subjective Dvorak T-numbers still support an intensity of around 60 kt, and that value is maintained as the initial wind speed for this advisory. An Air Force Reserve reconnaissance aircraft is scheduled to fly into the storm late tomorrow morning and early afternoon to better provide a better assessment of Pamela’s structure, intensity, and wind field.

The guidance suggests that the shear that has been plaguing Pamela should relax during the next 12-24 hours, allowing for strengthening. Nearly all of the statistical and dynamical model intensity guidance calls for strengthening, but they have trended toward a lower peak intensity primarily due to the fact that Pamela so far has not strengthened as much as expected. The NHC intensity forecast again calls for Pamela to become a hurricane overnight or early Tuesday, and shows the system nearing major hurricane strength before it reaches the coast of mainland Mexico early Wednesday. Although the official forecast is at the high end of the intensity guidance, it is supported by the GFS model which has been consistent in significantly deepening Pamela during the cyclone’s approach to Mexico on Tuesday and Tuesday night. After landfall, rapid weakening should occur as the system moves over the mountainous terrain of west-central Mexico, and Pamela is forecast to become a post-tropical remnant low or dissipate by Thursday.

Pamela is moving north-northwestward or 335/7 kt. The track forecast philosophy again remains unchanged this advisory. The cyclone is forecast to turn northward tonight as it reaches the western portion of a deep-layer subtropical ridge. A faster northeastward motion is expected by late Tuesday as Pamela recurves ahead of a broad mid-latitude trough moving into northwestern Mexico. The track guidance is in very good agreement on the overall evolution of the steering pattern, but there are still some differences in how quickly Pamela accelerates northeastward on Tuesday. Therefore, the NHC forecast is once again close to the various multi-model consensus aids.

Although the cyclone could dissipate over the mountainous terrain of Mexico, deep moisture associated with the system’s remnants are likely to spread over north-central and northeastern Mexico on Wednesday, and then move into portions of the south-central United States late Wednesday or Thursday.

Key Messages:

  • 1. Pamela is forecast to be near major hurricane intensity when it reaches the southwestern coast of Mexico on Wednesday morning, and life- threatening storm surge and dangerous hurricane-force winds are expected within the Hurricane Warning area. Residents in this area should follow any advice given by local officials.
  • 2. Pamela is expected to pass south of the southern tip of the Baja California peninsula as a hurricane on Tuesday and Tuesday night, and tropical-storm conditions are possible within the Tropical storm Watch area.
  • 3. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durgano along with southern portions of Baja California Sur Tuesday and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 4. Heavy rains associated with the remnants of Pamela are expected across portions of central Texas and southeastern Oklahoma late Wednesday and Thursday. This may result in flash and urban flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 17.9N 108.9W   60 KT  70 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  12/1200Z 19.2N 109.1W   70 KT  80 MPH - Category 1 (WSW Puerto Vallarta,MX)
 24H  13/0000Z 21.0N 108.5W   85 KT 100 MPH - Category 2 (WNW Puerto Vallarta,MX)
 36H  13/1200Z 23.1N 106.9W   95 KT 110 MPH - Category 2 (WSW Mazatlán,MX)
 48H  14/0000Z 26.1N 103.3W   40 KT  45 MPH - Tropical Storm (ESE Pamplona,MX)
 60H  14/1200Z 29.5N  99.5W   25 KT  30 MPH - Post Tropical (ESE Utopia,TX)
 72H  15/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 300 PM MDT Mon Oct 11, 2021 

Entrainment of dry mid-level air along with some modest north-northwesterly mid-level shear has caused Pamela’s low-level circulation to become slightly exposed just northwest of the somewhat ragged inner-core convection. Upper-level outflow, however, has improved in all quadrants, with a narrow equatorward outflow channel having developed in the eastern semicircle since the previous advisory. Pamela’s intensity was increased to 60 kt at 1800 UTC based on satellite current-intensity estimates of T4.0/65 kt from TAFB and T3.7/59 kt from UW-CIMSS ADT. However, 60 kt might be a little generous at the 2100 UTC advisory time, given that the low-level center has recently become partially exposed.

The motion estimate is northwestward or 320/06 kt. There is no significant change to the previous forecast track or reasoning. This current slow northwestward motion should continue this afternoon and evening as Pamela approaches the western periphery of a deep-layer subtropical ridge. Later tonight, the cyclone is expected to turn slowly northward, followed by a faster northeastward motion by Tuesday night as Pamela gets caught up in moderate southwesterly flow ahead of a deep-layer mid-latitude trough approaching from the northwest and west. This developing flow pattern is depicted quite well by all of the global and regional models, and should result in Pamela accelerating northeastward on Wednesday right up until the storm makes landfall along the west-central coast of Mexico. The new NHC forecast track has been shifted a little to the right again, and is close to the middle of the tightly packed TCVE, GFEX, NOAA-HCCA, and FSSE consensus track-model envelope.

The global and regional models are in very good agreement that the current slight southeastward tilt to the vortex column should abate within the next 6 hours or so, along with the dry mid-level air mixing out. As a result, deep convection should re-fire near the center later tonight, resulting in the development of an eyewall, which will create the necessary chimney effect to allow Pamela to resume its earlier rapid intensification trend. In fact, all of the models now show strengthening right up until the cyclone makes landfall on Wednesday due to the upper-level outflow pattern expanding, along with the development of poleward and equatorward outflow channels by late Tuesday. The new official intensity forecast is basically the same as the previous advisory, and lies near the upper-end of the intensity guidance. Pamela is still expected to become a dangerous major hurricane prior to landfall. After landfall occurs, rapid weakening is forecast due to the cyclone moving over the rugged terrain of west-central Mexico. However, the higher elevations of north-central Mexico could still receive tropical-storm force winds after Pamela moves well inland. Furthermore, deep moisture associated with Pamela will gradually overspread much of north-central and northeastern Mexico late on Wednesday, and then move into southern and central Texas on Thursday, enhancing the rainfall potential in those areas.

An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Pamela on Tuesday during the late morning and early afternoon to provide a better estimate of the cyclone’s intensity.

Key Messages:

  • 1. Pamela is forecast to be a major hurricane when it reaches the coast of west-central mainland Mexico on Wednesday, and life-threatening storm surge and dangerous hurricane-force winds are possible within the Hurricane Watch area. Residents in this area should monitor the progress of Pamela and follow any advice given by local officials.
  • 2. Pamela is expected to pass near or south of the southern tip of the Baja California peninsula as a hurricane Tuesday night and early Wednesday, and tropical-storm conditions are possible within the Tropical storm Watch area.
  • 3. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durgano along with southern portions of Baja California Sur Tuesday and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
  • 4. Heavy rains associated with Pamela are expected across portions of central Texas and southeastern Oklahoma late Wednesday and Thursday. This may result in flash and urban flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  11/2100Z 17.2N 108.5W   60 KT  70 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  12/0600Z 18.3N 109.0W   70 KT  80 MPH - Category 1 (WSW Manzanillo,MX)
 24H  12/1800Z 20.0N 108.9W   85 KT 100 MPH - Category 2 (WSW Puerto Vallarta,MX)
 36H  13/0600Z 22.0N 107.8W  100 KT 115 MPH - Category 3 (WSW Mazatlán,MX)
 48H  13/1800Z 24.3N 105.8W   45 KT  50 MPH - Tropical Storm (WNW La Aduana,MX)
 60H  14/0600Z 27.4N 102.1W   30 KT  35 MPH - Post Tropical (WNW Los Laureles,MX)
 72H  14/1800Z 31.2N  97.7W   20 KT  25 MPH - Post Tropical (ENE Fort Hood,TX)
 96H  15/1800Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 900 AM MDT Mon Oct 11, 2021 

Corrected to update Key Messages Pamela’s convective pattern has undergone a pronounced bursting phase since the previous advisory, including significant lightning activity in the inner-core region near the center, with formation of a Central Dense Overcast (CDO) now evident. However, the lightning ceased about 5 h ago and the CDO has recently become a little disheveled looking along with pronounced warming of the cloud tops compared to the much colder cloud tops colder than -85C just a few hours ago. The advisory intensity has been increased to 55 kt based on an average of satellite intensity estimates of T4.0/65 from TAFB, T3.0/45 kt from SAB, and T3.5/55 kt from UW-CIMSS ADT.

Pamela has slowed down significantly since the previous advisory, and the motion estimate is now northwestward or 320/07 kt. A northwestward motion should continue today as Pamela approaches an east-to-west-oriented subtropical ridge axis situated along 19-20N latitude. By late tonight, the storm is forecast to turn slowly northward, followed by a motion toward the northeast at a faster forward speed by Tuesday night. As Pamela gets caught up in the moderate southwesterly flow between the subtropical ridge to its south and an approaching mid-latitude trough to the northwest, the cyclone should continue to accelerate northeastward on Wednesday until Pamela makes landfall along the southwest coast of Mexico. The new NHC forecast track is a tad to the right of and slightly faster than the previous advisory track, and close to the middle of the tightly packed simple- and corrected-consensus track model envelope.

The recent disruption in Pamela’s convective pattern has likely been due the cyclone having entrained a slug of dry air. However, this convective hiatus will likely be short-lived due to the robust inner-core wind field noted in earlier ASCAT wind data, which should allow for Pamela to mix out any dry air. Moderate northerly shear is forecast to subside over the next 24 hours, giving way to the development of an upper-level anticyclone over the storm, along with an impressive outflow pattern developing in the northern semicircle. The combination of a tight inner-core wind field, low vertical shear, very warm sea-surface temperatures, and a moist mid-level environment should allow for Pamela to rapid intensify for the next 36 hours — possibly even right up until Pamela reaches the coast of Mexico. The latest official intensity forecast is very similar to the previous advisory, and is an average of the consensus intensity models IVCN and NOAA-HCCA, an remains at the high end of the intensity guidance. Pamela is expected to become a dangerous major hurricane prior to landfall. After inland occurs, rapid weakening is expected as the storm moves over the rugged terrain of west-central Mexico. However, higher elevations could still receive tropical-storm force winds after Pamela moves well inland.

An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Pamela Tuesday late morning and early afternoon.

Key Messages:

  • 1. Pamela is forecast to be a major hurricane when it reaches the coast of west-central mainland Mexico on Wednesday, and life-threatening storm surge and dangerous hurricane-force winds are possible within the Hurricane Watch area. Residents in this area should monitor the progress of Pamela and follow any advice given by local officials.
  • 2. Pamela is expected to pass near or south of the southern tip of the Baja California peninsula as a hurricane Tuesday night and early Wednesday, and tropical-storm conditions are possible within the Tropical storm Watch area.
  • 3. Heavy rains associated with Pamela are expected to move into the Mexican States of Sinaloa and western Durgano along with southern portions of Baja California Sur Tuesday and Wednesday. This will pose a threat of significant and life-threatening flash flooding and mudslides.
FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 16.8N 108.1W   55 KT  65 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  12/0000Z 17.8N 108.9W   70 KT  80 MPH - Category 1 (WSW Lázaro Cárdenas,MX)
 24H  12/1200Z 19.3N 109.3W   85 KT 100 MPH - Category 2 (WSW Puerto Vallarta,MX)
 36H  13/0000Z 21.1N 108.8W  100 KT 115 MPH - Category 3 (ESE Puerto Vallarta,MX)
 48H  13/1200Z 23.3N 107.1W  105 KT 120 MPH - Category 3 (WSW Mazatlán,MX)
 60H  14/0000Z 25.7N 104.9W   35 KT  40 MPH - Tropical Storm (WNW Las Playas,MX)
 72H  14/1200Z 29.1N 100.8W   25 KT  30 MPH - Post Tropical (WNW San Diego,MX)
 96H  15/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 900 PM MDT Sun Oct 10, 2021 

Satellite images indicate that Pamela is continuing to strengthen. The low-level center is on the northern edge of a growing area of deep convection, although there is still a fair bit of northerly shear as indicated by the V-shape to the cloud tops on infrared satellite imagery. Intensity estimates are rising, so the wind speed is set to 45 kt, closest to the latest TAFB classification.

The current moderate shear is forecast to relax some tomorrow as Pamela moves closer to the center of an upper-level high. Combined with the very warm waters in the path of the storm, this should set the stage for continued strengthening. Rapid intensification is also possible in a day or so when Pamela is in a shear minimum and likely has a better-developed inner core. The intensity forecast is raised from the previous one, although it remains below the corrected- consensus guidance. This could be a conservative forecast if the favorable environment shown by the GFS model materializes.

Pamela has slowed some tonight, now 295/10 kt. The steering pattern seems well defined for the next day or so with a ridge controlling the storm’s motion in a west-northwest to northwest direction. A broad mid-latitude trough causes the ridge to erode in a couple of days, forcing the cyclone to turn northward and northeastward by late Tuesday and move faster. The most significant guidance change is that more of the models are showing a quicker progression toward the coast of west-central Mexico. This makes meteorological sense as well, with a more powerful hurricane likely feeling the stronger upper-level southwesterly winds. The new forecast is adjusted toward the northeast beyond 24 hours, near or just behind the model consensus.

Key Messages:

  • 1. Pamela is forecast to be a major hurricane when it reaches the coast of west-central mainland Mexico on Wednesday, and it could bring life-threatening storm surge, flash flooding, and dangerous winds to a portion of that area. Residents in this area should monitor the progress of this system and ensure they have their hurricane plan in place.
  • 2. Pamela is expected to pass near or south of the southern tip of the Baja California peninsula as a hurricane Tuesday night or early Wednesday, and could bring strong winds and heavy rainfall to the extreme southern portion of the peninsula. Watches could be required for portions of this area early Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 15.9N 106.8W   45 KT  50 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  11/1200Z 16.5N 108.2W   55 KT  65 MPH - Tropical Storm (WSW Acapulco,MX)
 24H  12/0000Z 17.6N 109.3W   65 KT  75 MPH - Category 1 (WSW Lázaro Cárdenas,MX)
 36H  12/1200Z 19.0N 109.8W   75 KT  85 MPH - Category 1 (WSW Manzanillo,MX)
 48H  13/0000Z 20.7N 109.4W   85 KT 100 MPH - Category 2 (WSW Puerto Vallarta,MX)
 60H  13/1200Z 22.8N 108.0W  100 KT 115 MPH - Category 3 (ESE Cabo San Lucas,MX)
 72H  14/0000Z 25.5N 106.0W   50 KT  60 MPH - Tropical Storm (WSW Las Iglesias,MX)
 96H  15/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Sun Oct 10, 2021

The depression is gradually getting better organized this morning, as a large mass of deep convection with clouds tops colder than -80 degrees C has developed over the cyclone’s center. The initial advisory is held at 30 kt for this advisory and is based on the latest Dvorak intensity estimates from TAFB and SAB.

The initial motion of the depression is 290/15 kt. This west-northwestward motion is forecast to continue through tonight as the cyclone moves along the southern periphery of a mid-tropospheric ridge located over Mexico. Early this week, a short-wave trough is expected to dig southward over the western United States and northern Mexico which would produce a weakness in the ridge. This should cause the cyclone to make a gradual turn to the north Monday through Tuesday night, with a northeastward motion expected by Wednesday. The track model guidance is in very good agreement on this scenario and the latest NHC forecast track is little changed from the previous one. Based on the forecast track, the center of the cyclone should pass near or south of the southern tip of the Baja California peninsula Tuesday night or early Wednesday, then reach the coast of west-central mainland Mexico Wednesday night or early Thursday.

The recent increase in convection over the cyclone’s center suggests that a bout of intensification is soon to get underway, and the depression is expected to become a tropical storm later today. The environment surrounding the depression is ideal for strengthening over the next 2 to 3 days, and it is possible that the system could undergo a period of rapid intensification (RI) during that time. The latest GFS-SHIPS RI guidance continues to indicate a greater than 40 percent chance of a 65-kt increase in strength over the next 72 h. Based on a blend of the latest HCCA and IVCN intensity solutions and the SHIPS RI guidance, the latest NHC intensity forecast is similar to the previous one, indicating the cyclone reaching 95 kt in 72 h. Although not explicitly shown in the forecast, the system could become a major hurricane before reaching the coast of mainland Mexico.

Key Messages:

  • 1. The tropical cyclone is forecast to be at or near major hurricane intensity when it reaches the coast of west-central mainland Mexico by late Wednesday or early Thursday, and could bring life-threatening storm surge, flash flooding, and dangerous winds to a portion of that area. Residents in this area should monitor the progress of this system and ensure they have their hurricane plan in place.
  • 2. The tropical cyclone is expected to pass near or south of the southern tip of the Baja California peninsula as a hurricane Tuesday night or Wednesday, and could bring strong winds and heavy rainfall to the extreme southern portion of the peninsula. Watches could be required for portions of this area tonight or early Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 14.8N 104.7W   30 KT  35 MPH - Depression (WSW Acapulco,MX)
 12H  11/0000Z 15.4N 106.6W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 24H  11/1200Z 16.0N 108.2W   50 KT  60 MPH - Tropical Storm (WSW Acapulco,MX)
 36H  12/0000Z 17.1N 109.4W   65 KT  75 MPH - Category 1 (WSW Lázaro Cárdenas,MX)
 48H  12/1200Z 18.4N 110.0W   75 KT  85 MPH - Category 1 (WSW Manzanillo,MX)
 60H  13/0000Z 19.9N 109.9W   85 KT 100 MPH - Category 2 (WSW Puerto Vallarta,MX)
 72H  13/1200Z 21.8N 109.0W   95 KT 110 MPH - Category 2 (ESE Cabo San Lucas,MX)
 96H  14/1200Z 26.3N 105.5W   55 KT  65 MPH - Tropical Storm (WNW Los Muertos,MX)
120H  15/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM PDT Sat Oct 9, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A broad area of low pressure located a few hundred miles south-southwest of the Gulf of Tehuantepec continues to produce a large area of disorganized showers and thunderstorms. Environmental conditions are forecast to be conducive for development, and a tropical depression or tropical storm is expected to form within the next couple of days while the system moves west-northwestward at about 15 mph south of the coast of Mexico. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Fri Oct 8, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. Showers and thunderstorms remain disorganized in association with a broad area of low pressure located a few hundred miles south of Tehuantepec, Mexico. Environmental conditions are forecast to be conducive for development, and a tropical depression or tropical storm is expected to form within the next couple of days while the system moves westward to west-northwestward at about 15 mph south of the coast of Mexico. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Oct 8, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. Recent satellite images indicate that a broad area of low pressure has formed a few hundred miles south-southeast of Tehuantepec, Mexico. However, the associated shower and thunderstorm activity is currently disorganized. Environmental conditions are forecast to be conducive for development, and a tropical depression or tropical storm is expected to form by late this weekend or early next week while the system moves westward to west-northwestward at about 15 mph south of the coast of Mexico. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Oct 8 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave is producing disorganized showers and thunderstorms a few hundred miles south of the coasts of Guatemala and southern Mexico. Environmental conditions are forecast to be conducive for development, and a tropical depression or tropical storm is expected to form by late this weekend or early next week while the system moves westward to west-northwestward at about 15 mph south of the coast of Mexico. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Oct 8, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave is producing disorganized showers and thunderstorms a few hundred miles south of the coasts of El Salvador, Guatemala, and southern Mexico. Environmental conditions are forecast to be conducive for development, and a tropical depression is likely to form late this weekend or early next week while the system moves westward to west-northwestward at about 15 mph south of the coast of Mexico. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Thu Oct 7, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave moving offshore of the Pacific coast of Central America is producing disorganized showers and thunderstorms over portions of Central America and the adjacent eastern Pacific waters. Environmental conditions are forecast to be conducive for development over the next several days, and a tropical depression is likely to form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Thu Oct 7, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave emerging over the Pacific coast of Central America is producing disorganized showers and thunderstorms over portions of Central America and the adjacent eastern Pacific waters. Environmental conditions are forecast to be conducive for development over the next several days, and a tropical depression is likely to form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Oct 7, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave continues to produce disorganized cloudiness and thunderstorms over portions of Central America and the adjacent eastern Pacific waters. This system is expected to move westward and emerge over the eastern Pacific Ocean later today or tonight. Environmental conditions are forecast to be conducive for development over the next several days, and a tropical depression is likely to form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…high...70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Oct 7, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave is producing a large area of disorganized cloudiness and thunderstorms over portions of Central America and the adjacent eastern Pacific waters. This system is expected to move westward and emerge over the eastern Pacific Ocean later today or tonight. Environmental conditions are forecast to be conducive for gradual development over the next few days, and a tropical depression is likely to form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Wed Oct 6, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. A tropical wave is producing a large area of disorganized showers and thunderstorms over the southwestern Caribbean Sea and portions of Central America. This system is expected to move westward and emerge over the eastern Pacific Ocean in a day or so. Environmental conditions are forecast to be conducive for gradual development, and a tropical depression is likely to form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Wed Oct 6, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form off the coast of Central America and southern Mexico in a day or two. Environmental conditions are expected to be conducive for development thereafter, and a tropical depression could form over the weekend or early next week while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Wed Oct 6, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form off the coast of Central America and southern Mexico in a day or two. Environmental conditions are expected to be conducive for development thereafter, and a tropical depression could form over the weekend while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Wed Oct 6, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form off the coast of Central America and southern Mexico in a couple of days. Environmental conditions are expected to be conducive for development thereafter, and a tropical depression could form over the weekend while the system moves westward to west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Tue Oct 5, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form well off the coast of Central America and southern Mexico by the end of the week. Gradual development of the system is possible thereafter, and a tropical depression could form over the weekend while it moves westward to west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Tue Oct 5, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form well off the coast of Central America and southern Mexico by the end of the week. Gradual development of the system is possible thereafter, and a tropical depression could form over the weekend while it moves westward to west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Tue Oct 5, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure is forecast to form south of the southern coast of Mexico late this week. Gradual development of the system will be possible this weekend while it moves westward to west-northwestward at 10 to 15 mph, remaining offshore the coast of southern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Tue Oct 5, 2021

For the eastern North Pacific…east of 140 degrees west longitude:

  • 1. An area of low pressure could form south of the southern coast of Mexico late this week. Gradual development of the system will be possible this weekend while it moves westward to west-northwestward at 10 to 15 mph, remaining offshore the coast of southern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

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