Tropical Storm Sandra

Tropical Depressdion Sandra Track 0700 Hours November 09 2021
Tropical Depressdion Sandra Track 0700 Hours November 09 2021

Tropical Storm Sandra Wind Speed FieldTropical Storm SandraNWS National Hurricane Center Miami FL 700 AM PST Tue Nov 09, 2021 (see Tuesday video below)

Bursts of deep convection have been forming well to the northeast of Sandra’s exposed surface center since Monday evening, but haven’t been persistent, during the past 12 hours, to be considered as organized convection. Accordingly, the system will likely be classified as a remnant low this afternoon. Stiff, persistent southerly shear and a stabilizing surrounding atmosphere should cause further weakening, and the remnant low is forecast to open up into a trough on Wednesday.

Sandra has continued to move a little south of due west, or 260/11 kt during the past 6 hours. A strengthening ridge to the north of the cyclone should influence a westward to west-southwestward through Wednesday. The official NHC forecast is in line with the various consensus aids and lies close to the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 14.6N 120.7W   25 KT  30 MPH - Depression (WSW Puerto Escondido,MX)
 12H  10/0000Z 14.1N 122.6W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
 24H  10/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 700 AM PST Mon Nov 08, 2021 

Conventional satellite imagery and a 1206 UTC SSMIS microwave overpass indicate that Sandra’s less-defined surface circulation remains sheared to the southwest of the warming cloud top convective mass. The Dvorak satellite intensity estimates from TAFB and SAB are unchanged from the previous 6 hr estimates, and the initial intensity is held at 35 kt.

UW-CIMSS shear analysis and the statistical SHIPS models (ECMWF and GFS) indicate that the 15-20 kt of southwesterly shear will persist and increase in magnitude by Tuesday evening while the surrounding thermodynamic environment gradually becomes more stable. Given these current and predicted inhibiting factors, Sandra is forecast to become a depression by this evening, and degenerate into a remnant low by Tuesday evening. The NHC intensity forecast is an update of the previous one, and is based on the the NOAA HFIP corrected consensus model and agrees with the GFS and ECMWF global model solutions.

The initial motion is estimated to be west-northwestward, or 290/6 kt. A subtropical ridge located to the north of Sandra should steer the cyclone toward the west-northwest through this evening. Through the remainder of the forecast, the global models show the aforementioned low-to mid-level ridge building slightly toward the northwest of Sandra which should cause the cyclone to turn toward the west by early Tuesday. The official track forecast follows suit and is once again adjusted a bit toward the left of the previous forecast and is nudged closer to the TCVE simple multi-model forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 14.6N 116.8W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 12H  09/0000Z 15.0N 117.9W   30 KT  35 MPH - Depression (WSW Puerto Escondido,MX)
 24H  09/1200Z 15.1N 119.7W   30 KT  35 MPH - Depression (WSW Puerto Escondido,MX)
 36H  10/0000Z 14.7N 122.2W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
 48H  10/1200Z 14.3N 125.0W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
 60H  11/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 700 PM PST Sun Nov 07, 2021

Sandra was briefly devoid of convective activity earlier today, but its organization has somewhat improved during the past several hours. Bursts of deep convection have been noted in the northeastern quadrant of the tropical cyclone. The well-defined low-level center became exposed earlier today due to 20 kt of southwesterly deep-layer shear over Sandra, but the center has recently moved closer to the edge of a small convective cloud mass. The objective and subjective satellite estimates range from 30-35 kt, and the initial intensity is held at 35 kt for this advisory. Hopefully, a scatterometer pass samples the storm later tonight to help assess its intensity and structure.

A ridge to the north and east of Sandra is steering the cyclone west-northwestward, and its estimated motion is 285/10 kt. Sandra is expected to gradually turn westward over the next couple of days, as the vertically shallow circulation becomes increasingly steered by the low-level flow. Little change is noted in the latest track guidance, and the official NHC track forecast is very similar to the previous one, with just slight southward adjustments based on the consensus aids. Moderate (15-20 kt) southwesterly shear is forecast to persist over Sandra for the next 12-24 h, then strengthen thereafter. Given that Sandra has already struggled to maintain organized convection, the system is likely to be short-lived. The cyclone is expected to weaken on Monday as the increasing shear strips away its remaining convection. Sandra should degenerate to a post-tropical remnant low early Tuesday and then open up into a trough and dissipate by Wednesday. The latest NHC intensity forecast remains in good agreement with the HCCA and IVCN consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 14.2N 116.0W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 12H  08/1200Z 14.7N 117.2W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 24H  09/0000Z 15.2N 118.7W   30 KT  35 MPH - Depression (WSW Puerto Escondido,MX)
 36H  09/1200Z 15.4N 120.5W   30 KT  35 MPH - Post Tropical (WSW Puerto Escondido,MX)
 48H  10/0000Z 15.1N 123.0W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
 60H  10/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 100 PM PST Sun Nov 07, 2021

This afternoon, deep-convective activity has decreased in coverage and intensity, shearing off to the east and revealing a well-defined low-level circulation. Even though the convection has waned, an earlier 1549 UTC ASCAT-A pass revealed a fairly large region of 30-35 kt winds primarily to the east of the circulation. Based primarily on the scatterometer data, TD 19-E was upgraded to 35-kt Tropical Storm Sandra at 1800 UTC and that will be the intensity for this advisory. It should be noted that the satellite presentation was better organized this morning, when both SAB and TAFB provided CI 2.5/35 kt estimates, and it is likely this system was already tropical storm earlier today.

The exposed low-level circulation has been moving left of the previous forecast track this afternoon, with the current estimated motion at 285/10 kt. The track guidance is insistent that a more poleward motion will resume soon, but its possible the storm’s direction of motion is dependent on additional down-shear convective bursts helping to tug the center more poleward. As the system becomes more vertically shallow, the west-northwest motion should bend more westward and then west-southwestward as the circulation gradually decays. The track guidance this cycle is further to the left in the short-term, mainly based on the initial motion, but corrects to near the same place by the end of the forecast period. The latest NHC track forecast has also been shifted further south early on, but ends up near the previous one by 60 hours, close to the tightly clustered consensus aids.

Assuming that convection will redevelop near or east of the center, possibly during the diurnal convective maximum tonight, Sandra is expected to maintain its intensity for the next 12-24 hours. Thereafter, increasing vertical wind shear should help to import drier mid-level air that should finish off any additional convection. Forecast simulated IR imagery from the GFS and ECMWF suggests Sandra becoming devoid of convection by 48-60 h, and the latest NHC forecast still shows the cyclone becoming a post-tropical remnant low by this time frame. The NHC intensity forecast is in decent agreement with the intensity guidance and is quite similar to the latest SHIPS/LGEM, though remains lower than the HWRF/HMON runs.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 14.0N 115.2W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 12H  08/0600Z 14.5N 116.1W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 24H  08/1800Z 15.3N 117.5W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 36H  09/0600Z 15.7N 119.0W   30 KT  35 MPH - Depression (WSW Puerto Escondido,MX)
 48H  09/1800Z 15.5N 121.2W   30 KT  35 MPH - Post Tropical (WSW Puerto Escondido,MX)
 60H  10/0600Z 15.0N 124.0W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
 72H  10/1800Z...DISSIPATED

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

The depression’s convective pattern remains quite disorganized this morning. Although there are several blobs of convection and areas of colder cloud tops, there is no evidence of curved banding in both convection satellite and recent microwave data. It is difficult to tell if the circulation has become any better defined since the ASCAT overpass last evening. Hopefully the ASCAT instrument will provide a better assessment of the system’s structure and strength later today. Subjective and objective Dvorak intensity estimates are in the 30-35 kt range, and given the lack of organization and earlier scatterometer data, the initial wind speed is held at 30 kt.

The center of the depression has been difficult to locate this morning, but recent fixes and continuity from the previous advisory suggest it is moving westward or 275/12 kt. A deep-layer ridge to the north of the depression should continue to steer it westward to west-northwestward during the next several days. The model envelope has trended a little farther north this cycle, but the NHC forecast remains similar to the previous advisory, along the southern edge of the envelope closest to the GFS, HWRF, and HMON solutions.

The depression is forecast to remain in low wind shear conditions during the next several days, but a drier and more stable airmass just to the north is likely to limit intensification. The NHC forecast is unchanged from the previous advisory and still shows the system reaching tropical storm status within the next couple of days. By 72 hours, the vertical shear is predicted to increase and the mid-level humidity in the surrounding environment is forecast to decrease. These negative factors should cause weakening and degeneration of the system to a remnant low by 96 hours, and dissipation by day 5. This is supported by the GFS and ECMWF models which weaken the system within the ITCZ after midweek.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z  8.2N 101.4W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 12H  08/0000Z  8.7N 103.3W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 24H  08/1200Z  9.2N 105.7W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 36H  09/0000Z  9.5N 108.1W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 48H  09/1200Z  9.8N 110.6W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 60H  10/0000Z 10.1N 113.0W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 72H  10/1200Z 10.1N 115.4W   30 KT  35 MPH - Post Tropical (WSW Puerto Escondido,MX)
 96H  11/1200Z 10.2N 120.3W   25 KT  30 MPH - Post Tropical (WSW Puerto Escondido,MX)
120H  12/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Sat Nov 06, 2021

After struggling to produce much in the way of deep convection yesterday, a large nocturnal deep convective burst, with overshooting cloud tops as cold as -85 C, occurred near the estimated center of the depression, though this activity is beginning to wane. An 0815 UTC AMSR2 microwave pass also suggested modest organization under the cirrus, with some banding features present in the deep convection. While last night’s scatterometer derived winds only topped out at 27 kt, the most recent subjective Dvorak intensity estimate from TAFB is at T2.0/30 kt. The latest objective UW-CIMSS ADT estimate is even higher at T2.5/35 kt. These estimates support bringing the intensity back up to 30 kt for this advisory.

Using both scatterometer and microwave fixes, the depression has maintained a south of due west heading over the past 12-24 hours, with the latest motion estimated at 260/12 kt. This general heading is expected to continue for the next several days with a gradual bend poleward in the latter half of the forecast period as the cyclone rounds the southern side of a expensive mid-level ridge centered over Mexico. The latest NHC track forecast has been adjusted just a bit faster, blending the tightly clustered consensus aids TVCE and HCCA.

The depression’s overnight convective burst was well anticipated by the both the GFS and ECMWF simulated IR brightness temperature and both models show more persistent activity continuing through the forecast period. Despite this factor, neither model shows much, if any, additional strengthening. This result is interesting, since both the GFS- and ECMWF-based SHIPS guidance indicate low 200-850 hPa vertical wind shear, 27-28 C sea-surface temperatures, and a fairly moist mid-level environment. One factor possibly limiting the intensity forecast is the possibility of higher westerly mid-level shear undercutting the more favorable deep-layer shear. In addition, the tropical cyclone is forecast to remain at fairly low-latitude which can sometimes limit vortex spin-up in a lower Coriolis environment. Even the overzealous HWRF model has come back down to earth, showing only a peak intensity as a more modest tropical storm. The latest NHC intensity forecast does still show TD18-E eventually becoming a tropical storm in 36 h, but does not show any additional development. This forecast is a blend between the slightly higher intensity consensus aids (IVCN, HCCA) with the more pessimistic global model guidance (UKMET, GFS, ECMWF) which do not indicate any additional intensification over the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z  8.4N  96.6W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 12H  07/0000Z  8.2N  98.3W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 24H  07/1200Z  8.1N 100.7W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 36H  08/0000Z  8.4N 103.2W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 48H  08/1200Z  8.9N 105.5W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 60H  09/0000Z  9.5N 108.0W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 72H  09/1200Z 10.0N 110.4W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 96H  10/1200Z 10.5N 115.5W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)
120H  11/1200Z 10.7N 121.2W   35 KT  40 MPH - Tropical Storm (WSW Puerto Escondido,MX)

NWS National Hurricane Center Miami FL 1000 AM CDT Fri Nov 05, 2021

The convective structure with the depression this morning remains disheveled, with only scattered convection pulsing around the circulation without much organization. The latest subjective Dvorak satellite estimates are T2.0/30 kt from TAFB and T1.5/25 kt from SAB, while the most recent UW-CIMSS ADT estimate was T2.1/31 kt. A blend of these data support maintaining the intensity at 30 kt this advisory.

Early morning visible satellite imagery suggests that the system is moving south of due west, with the latest motion estimate at 260/8 kt. As an amplified short-wave trough located over the Gulf of Mexico propagates eastward, a mid-level ridge ridge centered near the Baja California peninsula is expected to expand eastward over Mexico. This feature should dominate the steering pattern over the depression through the forecast period, leading to a general westward motion but at a gradually accelerating forward speed. Because the depression is quite shallow currently, low-level flow in association with a developing gale-force gap wind event in the Gulf of Tehuantepec may also assist the system in losing a bit more latitude over the next 24-36 hours. After 48 hours, a weakness under the ridge from an downstream disturbance may allow the depression to gain back a bit of latitude. The track guidance remains in fairly good agreement, though differences in speed are seen between the slower GFS versus the faster ECMWF guidance, and another southward shift has taken place. The official NHC track forecast is a bit further south and a touch faster compared to the previous one, following the consensus aids TVCE and HCCA.

The current poor organization of the convection argues against any short-term intensity changes. While deep-layer (200-850 hPa) vertical wind shear is expected to remain low, higher mid-level shear may prevent better convective organization over the next 36-48 hours. While mid-level relative humidity is forecast to be sufficently moist, visible satellite imagery suggests stable stratocumulus inflow from the south, while the aforementioned gap wind event to the north may also contribute to a less-than-optimal thermodynamic environment. The official NHC intensity forecast now shows no intensification over the next 36 hours with only gradual intensification thereafter, favoring the more pessimistic guidance. If the latest ECMWF and LGEM guidance are correct, the depression may fail to intensify at all over the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z  9.4N  92.4W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 12H  06/0000Z  9.2N  93.5W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 24H  06/1200Z  8.9N  95.4W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 36H  07/0000Z  8.7N  97.5W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 48H  07/1200Z  8.7N  99.7W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 60H  08/0000Z  9.2N 102.0W   40 KT  45 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 72H  08/1200Z  9.8N 104.4W   45 KT  50 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 96H  09/1200Z 10.9N 109.4W   50 KT  60 MPH - Tropical Storm (WSW Puerto Escondido,MX)
120H  10/1200Z 11.3N 114.2W   55 KT  65 MPH - Tropical Storm (WSW Puerto Escondido,MX)

NWS National Hurricane Center Miami FL 400 AM CDT Fri Nov 05, 2021

The depression has not become much better organized since yesterday. Some small clusters of deep convection have formed to the northeast and east of the center, and there are some thin convective banding features over the southern and western portions of the circulation. Cirrus-level outflow from the system is rather weak at this time. The advisory intensity estimate is held at 30 kt which is in general agreement with the latest Dvorak analyses from TAFB and SAB, along with earlier scatterometer observations. The latter data, however, suggest that this may be a slightly generous estimate.

Latest center fixes indicate a continued westward motion, or around 265/6 kt. A mid-level ridge associated with a large high pressure system centered over western Mexico should provide the primary steering mechanism for the cyclone during the forecast period. A mainly westward motion at a somewhat faster forward speed is expected, as the system encounters slightly stronger easterlies on the south side of the ridge within the next couple of days. The dynamical track guidance is in fairly good agreement, although the GFS model is a bit of a northern outlier. The official forecast track is similar to the previous one, and close to the model consensus.

Since it is still not very well organized, the tropical cyclone is not expected to strengthen much through today. Although the environment is seemingly conducive for strengthening, the model guidance is not very aggressive in showing intensification during the next few days. This may be partially due to a lack of mid- to upper-level instability ,as suggested by the decay-SHIPS output. The official forecast, like the previous one, shows only slow strengthening beginning tomorrow, following the intensity model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z  9.7N  91.7W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 12H  05/1800Z  9.5N  92.6W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 24H  06/0600Z  9.2N  94.2W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 36H  06/1800Z  9.0N  96.1W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 48H  07/0600Z  8.9N  98.3W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 60H  07/1800Z  9.1N 100.7W   40 KT  45 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 72H  08/0600Z  9.5N 103.1W   45 KT  50 MPH - Tropical Storm (WSW Puerto Escondido,MX)
 96H  09/0600Z 10.6N 108.0W   50 KT  60 MPH - Tropical Storm (WSW Puerto Escondido,MX)
120H  10/0600Z 11.5N 112.5W   55 KT  65 MPH - Tropical Storm (WSW Puerto Escondido,MX)

NWS National Hurricane Center Miami FL 1000 AM CDT Thu Nov 04, 2021

The area of low pressure we have been tracking since it formed several days ago over the southwestern Caribbean Sea has moved over the far eastern Pacific and gradually become better-defined over the past couple of days. In addition, the convective organization has steadily increased. An ASCAT-C overpass earlier this morning showed that the surface low was slightly elongated. However, the deep convection has persisted near, or just east of that low for several hours since that time. First light visible satellite imagery also indicates that the circulation is well-defined. Therefore, advisories are being initiated for Tropical Depression Eighteen-E. The ASCAT pass also showed peak winds of 28 kt associated with the system, and a blend of the latest Dvorak intensity estimates from TAFB and SAB suggest an initial advisory intensity of 30 kt.

The initial motion of the depression is 280/7 kt. The cyclone is located to the south of a broad mid-tropospheric ridge extending across southern Mexico and much of the eastern Pacific basin. This feature should steer the depression generally westward for most of the forecast period, along with a gradual increase in forward speed. By day 5, a turn to the west-northwest may occur, as the cyclone becomes situated along the southwestern portion of the ridge. The track model guidance is in good agreement on this scenario, and the NHC track forecast is near the various multi-model consensus solutions.

The environment surrounding and ahead of the depression appears generally favorable for strengthening with ample atmospheric moisture and SSTs of 27 to 28 degrees C. The only inhibiting factor to strengthening may be the westerly shear vector, which although should remain under 10 kt, when combined with the cyclone’s increasing westerly forward motion may cause convection to periodically get stripped to its east of its center. Based on these conditions, the model guidance indicates a slow and steady pace of strengthening over the next several days, and NHC follows suit with an intensity forecast near the IVCN and NOAA-HCCA consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z  9.4N  90.0W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 12H  05/0000Z  9.6N  90.9W   30 KT  35 MPH - Depression (WSW Nosara,Costa Rica)
 24H  05/1200Z  9.4N  92.0W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 36H  06/0000Z  9.2N  93.4W   35 KT  40 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 48H  06/1200Z  9.0N  95.2W   40 KT  45 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 60H  07/0000Z  9.0N  97.3W   40 KT  45 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 72H  07/1200Z  9.0N  99.6W   45 KT  50 MPH - Tropical Storm (WSW Nosara,Costa Rica)
 96H  08/1200Z  9.7N 104.1W   50 KT  60 MPH - Tropical Storm (WSW Puerto Escondido,MX)
120H  09/1200Z 11.1N 108.5W   55 KT  65 MPH - Tropical Storm (WSW Puerto Escondido,MX)

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Video: Tropical Weather Forecast – November 8, 2021