Tropical Storm Terry

Tropical Depression Terry Track 0700 Hours November 10 2021
Tropical Depression Terry Track 0700 Hours November 10 2021

Tropical Storm Terry Wind Speed FieldTropical Storm Terry – NWS National Hurricane Center Miami FL 700 AM PST Wed Nov 10, 2021 (see Tuesday video below)

Conventional satellite imagery shows that Terry’s cloud pattern has changed little overnight, and the depression remains a poorly organized tropical cyclone. A fortuitous 1142 UTC SSMIS microwave pass consisted of fragmented curved bands south and well to the west of a southwest to northeast elongated surface center. The initial intensity is held at 25 kt for this advisory.

Dry, stable air intrusion and slightly cooler oceanic sea surface temperatures should inhibit any further strengthening from occurring through the forecast period. The large-scale models and the statistical SHIPS intensity guidance are in agreement with Terry degenerating into a remnant low by Friday, if not sooner, and dissipating over the weekend. The official intensity forecast is basically an update of the previous one, following a compromise of the aforementioned guidance and the IVCN intensity consensus aid.

Terry’s initial motion is still estimated to be 270/13 kt. There is no change to the track forecast reasoning. Terry is expected to continue on a westward heading during the next few days within the low- to mid-level steering flow produced by a subtropical ridge to the north of the cyclone. The NHC track forecast, once again, follows the better performing HCCA and TVCE multi-model guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 11.7N 116.9W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 12H  11/0000Z 11.6N 119.0W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 24H  11/1200Z 11.4N 121.6W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 36H  12/0000Z 11.2N 124.3W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 48H  12/1200Z 10.9N 127.1W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
 60H  13/0000Z 10.6N 129.9W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
 72H  13/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM MST Tue Nov 09, 2021

Convective bursts continue to pulse over the western portion of Terry’s circulation. An 0846 UTC AMSR2 microwave overpass showed that the overall convective organization is poor and that the low-level circulation appears broad. Although Dvorak satellite intensity estimates still support tropical storm intensity, scatterometer data over the past 24 hours have revealed winds around 25 kt. Given the typically undersampling of the ASCAT instrument the intensity is held at 30 kt, but this could be generous.

Although the shear that has been plaguing Terry could decrease over the next day or so, intrusions of dry mid-level air are likely to continue to prevent strengthening. Additionally, as the storm moves westward later this week the overall environment is forecast to become more stable, and this is expected to result in Terry weakening and degenerating into a remnant low or trough of low pressure by day 4. That is supported by the ECMWF and UKMET models, however the GFS continues to show the possibility of re-strengthening. Based on current trends, the official forecast continues to place more weight on the ECMWF/UKMET solutions.

Terry continues to move a little north of due west or 280/12 kt. The cyclone should maintain a general westward heading over the next few days as it moves along the southern periphery of a strong subtropical ridge over the eastern Pacific. Although the dynamical models agree on the overall track scenario, there is some along- track spread, therefore the official forecast remains close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 11.1N 111.7W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 12H  10/0000Z 11.3N 113.5W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 24H  10/1200Z 11.5N 115.9W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 36H  11/0000Z 11.4N 118.4W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 48H  11/1200Z 11.2N 120.8W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 60H  12/0000Z 10.8N 123.5W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
 72H  12/1200Z 10.5N 126.2W   20 KT  25 MPH - Post Tropical (WSW Acapulco,MX)
 96H  13/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM MST Mon Nov 08, 2021

Terry has become less organized since yesterday and it appears that this is the from a combination of mid-level shear and the entrainment of some drier and more stable air from the north. Early light-visible satellite imagery reveals a couple of linear lines of deep convection, but the low cloud motion suggests that the circulation may be less defined. The initial intensity has been lowered to 30 kt, and is based on earlier scatterometer data and a TAFB Dvorak classification of T2.0. Hopefully the ASCAT instrument will provide data over the system this afternoon to determine if a well-defined center still exists.

Terry is moving west-northwestward or 290/13 kt. The track forecast reasoning remains unchanged as a well-established strong deep-layer ridge to the north of Terry is expected to steer the cyclone westward to west-northwestward during the next few days. The dynamical model guidance is in agreement on this scenario but the updated NHC track forecast has been adjusted slightly northward to be closer to the various consensus aids.

The mid-level shear that has been plaguing Terry is forecast to continue during the next day or two. This is likely to result in some additional weakening during that time. Although some of the guidance suggests that Terry could reach a more favorable environment later in the period, the current structure of the system suggests that there will not be enough left of the cyclone to take advantage of that. Therefore, the NHC forecast continues to follow the ECMWF and UKMET models which depict weakening and dissipation by day 4. It is possible that Terry will loose tropical cyclone status much sooner, either due to a lack of organized convection or loss of a well-defined center.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 10.1N 106.6W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 12H  09/0000Z 10.6N 108.6W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 24H  09/1200Z 11.2N 111.0W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 36H  10/0000Z 11.4N 113.5W   30 KT  35 MPH - Tropical Depression (WSW Acapulco,MX)
 48H  10/1200Z 11.5N 116.1W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 60H  11/0000Z 11.5N 118.9W   25 KT  30 MPH - Tropical Depression (WSW Acapulco,MX)
 72H  11/1200Z 11.3N 121.6W   20 KT  25 MPH - Post Tropical (WSW Acapulco,MX)
 96H  12/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 900 PM CST Sun Nov 07, 2021

Terry remains a very low latitude tropical storm. The system has generally changed little during the past several hours, with the cloud pattern consisting of a ragged central dense overcast feature and broken curved bands that are most organized in the northwestern quadrant. The latest Dvorak estimates from TAFB, SAB, and CIMSS at the University of Wisconsin range from 35 to 50 kt, and the initial intensity is nudged up to 40 kt based on that data.

The track forecast reasoning is unchanged. The storm is moving west-northwestward at 12 kt, and it is expected to move westward to west-northwestward through Monday. Thereafter, a due westward motion is expected as Terry moves on the south side of a strong low- to mid-level ridge. The models all show a similar theme, but there is some cross- and along-track spread. The new track forecast is a touch north of the previous one to come into better agreement with the latest consensus aids.

Now that Terry has pulled away from the Gulf of Tehuantepec, where dry and stable air was entraining into the system, some slight additional strengthening is possible in the short term as the large scale conditions remain generally favorable. However, in a couple of days, increasing southerly shear will likely end the opportunity for strengthening and cause a gradual decay. The GFS and ECMWF both show Terry’s convection losing organization around the middle of the week and those models also show the system dissipating within the ITCZ in 4 or 5 days. There is a large spread in the intensity models, but given the expected environmental conditions, the NHC intensity forecast continues to lie near the low end of the guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z  9.0N 103.8W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  08/1200Z  9.5N 105.8W   45 KT  50 MPH - Tropical Storm (WSW Acapulco,MX)
 24H  09/0000Z 10.0N 108.1W   45 KT  50 MPH - Tropical Storm (WSW Acapulco,MX)
 36H  09/1200Z 10.4N 110.7W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 48H  10/0000Z 10.6N 113.2W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 60H  10/1200Z 10.6N 115.9W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 72H  11/0000Z 10.7N 118.4W   30 KT  35 MPH - Depression (WSW Acapulco,MX)
 96H  12/0000Z 10.5N 124.1W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
120H  13/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 300 PM CST Sun Nov 07, 2021

The overall organization of the depression has become slightly better since this morning. Recent one-minute GOES-16 visible satellite imagery suggests that the center is better defined and there has been a persistent cluster of convection just southeast of the estimated center since this morning. Subjective Dvorak intensity estimates from SAB and TAFB were unchanged at 30-35 kt, but ADT and SATCON estimates are in the 39-42 kt range. Although a 1410 UTC ASCAT-A overpass missed the center, it did reveal an area of 30-40 kt winds along the edge of the swath, however the strongest vectors were flagged due to rain contamination. Given the recent improvement in both center definition and the persistent convection near that feature, the intensity is increased to 35 kt for this advisory.

Terry is moving just north of due west at 275/12 kt. The steering currents ahead of the storm remains well established with a strong deep-layer ridge located to the north. That feature should guide Terry westward to west-northwestward at about 12 kt for the next several days. The NHC track guidance is in good agreement on the overall scenario, but there is spread regarding the cyclone’s forward speed. The NHC track leans closer to the slightly more southern and deeper GFS solution. This is along the southern side of the guidance envelope and fairly close to the speed of the various consensus aids.

The storm is forecast to remain within low vertical wind shear conditions over the next couple of days, however it is likely to ingest drier and more stable air that is located just to the north. That stable air is expected to keep significant strengthening from occurring, but some limited intensification is possible during the next day or two. By Tuesday night or Wednesday, environmental conditions are forecast become more hostile with an increase in vertical shear and decreasing mid-level humidity. Those factors should cause weakening and degeneration to a remnant low by 96 hours. The global models indicate that the system will open up into a trough along the ITCZ by day 5 and that is reflected in the official forecast.

FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z  8.5N 102.6W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 12H  08/0600Z  8.9N 104.4W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 24H  08/1800Z  9.4N 106.9W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 36H  09/0600Z  9.7N 109.4W   40 KT  45 MPH - Tropical Storm (WSW Acapulco,MX)
 48H  09/1800Z  9.8N 111.7W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 60H  10/0600Z  9.9N 114.2W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 72H  10/1800Z 10.0N 116.7W   30 KT  35 MPH - Depression (WSW Acapulco,MX)
 96H  11/1800Z 10.0N 121.8W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
120H  12/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM MST Sun Nov 07, 2021

The broad area of low pressure we have been monitoring for the last several days well south of the Baja California Peninsula has improved in organization this morning. Overnight scatterometer data suggested that a better defined center was trying to develop close to the deep convection. Microwave data from an 0857 UTC AMSR2 pass also indicated low-level cloud curvature on the 37-GHz channel, suggesting a well-defined center had formed. Indeed, first light 1-min visible imagery from a GOES-17 mesoscale domain now shows a tight low-level swirl located just to the west of a new burst of deep convection. All these data suggest the system’s circulation is now well-defined. Therefore, advisories are being initiated on Tropical Depression Nineteen-E. Subjective Dvorak estimates from both TAFB and SAB are both at CI 2.5/35 kt, suggesting the depression may already be close to tropical storm intensity.

The initial motion of the depression is estimated to be 290/7 kt, though uncertainty exists since the center only recently became well-defined. The system currently lies along the southwestern periphery of a mid-level ridge centered over Mexico. This synoptic pattern should allow the depression to maintain a west-northwest motion over the next 12-24 hours while it remains vertically coupled to the deep-convection. Afterwards, the remaining deep convection is expected to dissipate and the leftover shallow vortex is expected to be increasingly steered around a low-level ridge offshore of the west coast of Mexico. This pattern should cause the cyclone to turn westward and then west-southwestward over the remainder of its lifespan. The track guidance is in fairly good agreement on this general solution, and the NHC official track lies close to the consensus aids TVCN and HCCA.

As mentioned above, the subjective satellite estimates already suggest that this system could be near tropical storm intensity and the peak wind from the overnight scatterometer data was 31 kt. While the system is currently battling about 20-25 kt of south-southwesterly vertical wind shear, this magnitude is not expected to change much during the next 12-24 hours. Thus, there is an opportunity for some slight intensification, which is reflected in the NHC intensity forecast which takes the system up to a 35-kt tropical storm by tonight. However, increasing shear and a drying mid-level environment should result in weakening beginning by 36 hours with the storm forecast to become a remnant low by Tuesday. The NHC intensity forecast is a bit above the consensus aids, but a bit below the latest HWRF/HMON runs which suggests a slightly higher 40-45 kt peak intensity.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 13.7N 113.7W   30 KT  35 MPH - Depression (WSW Acapulco,MX)
 12H  08/0000Z 14.3N 114.7W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 24H  08/1200Z 15.1N 115.8W   35 KT  40 MPH - Tropical Storm (WSW Acapulco,MX)
 36H  09/0000Z 15.6N 117.3W   30 KT  35 MPH - Depression (WSW Acapulco,MX)
 48H  09/1200Z 15.6N 119.1W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
 60H  10/0000Z 15.3N 121.6W   25 KT  30 MPH - Post Tropical (WSW Acapulco,MX)
 72H  10/1200Z...DISSIPATED

Article Resources:

Video: Tropical Weather Forecast – November 8, 2021