Tropical Storm Dalila

Tropical Storm Dalila Track 0200 Hours July 24 2019
Tropical Storm Dalila Track 0200 Hours July 24 2019

Tropical Storm Dalila Satellite 0800 Hours July 24 2019Tropical Storm Dalila – NWS National Hurricane Center Miami FL 200 AM PDT Wed Jul 24,  2019

Dalila has maintained a robust low-level circulation based on recent scatterometer wind data, but those data also indicate that Dalila’s peak winds had decreased to 27-30 kt despite a sharp increase in deep convection near and southeast of the center. UW-CIMSS ADT and SATCON estimates suggest a higher intensity of 35-44 kt. However, it appears that the cooler water that the cyclone is moving over has stabilized the boundary layer, which is not allowing the normal downward mixing of stronger winds aloft to reach the surface. Given the lower ASCAT wind data, Dalila has been downgraded to a 30-kt tropical depression.

The initial motion estimate is 315/05 kt. There is no significant change to the previous track and intensity forecast philosophies. Dalila is expected to move northwestward today, followed by a turn toward the west-northwest on Thursday when the weakening cyclone becomes more shallow and comes under the influence of easterly trade wind flow. The cyclone is now moving over 25 deg C sea-surface temperatures, with cooler water and more stable air still ahead of Dalila. As a result, convection is expected to gradually wane during the next 24 hours, accompanied by a steady spin-down of the vortex, which should result in the system degenerating into a post-tropical remnant low by Thursday morning, if not sooner. The NHC track and intensity forecasts closely follow the consensus models HCCA and IVCN, respectively.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 19.8N 118.8W   30 KT  35 MPH - (WNW Isla Clarión, MX)
 12H  24/1800Z 20.4N 119.5W   25 KT  30 MPH - (WNW Isla Clarión, MX)
 24H  25/0600Z 21.1N 120.6W   25 KT  30 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)
 36H  25/1800Z 21.8N 121.8W   20 KT  25 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)
 48H  26/0600Z 22.2N 122.9W   20 KT  25 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)
 72H  27/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Tue Jul 23, 2019

Dalila continues to battle 15-20 kt of northerly shear with deep convection displaced across the southern semicircle of the storm. Satellite imagery indicates that there are multiple low level swirls encircling a mean center that is located just north of the edge of the convection. The latest Dvorak intensity estimates from both TAFB and UW-CIMMS support maintaining a 35 kt initial intensity for this advisory.

The initial motion is 330/07. A mid-level ridge over the southwestern United States will steer the cyclone to the northwest through much of tonight. As the system weakens, it will become steered by an increasing component of the low-level flow, resulting in a turn more to the west-northwest Wednesday and Thursday. Similar to the past few model cycles, the latest guidance has shifted slightly to the west, and therefore the official forecast track has also been adjusted a little in that direction.

Dalila is approaching the 26 C isotherm and the center is forecast to cross it in about 12 hours, which should cause a weakening trend to begin by tonight. In addition, the current shear is not expected to decrease significantly in the next day or so, and during that time the cyclone will be moving into a drier, more stable environment. These factors should cause Dalila to lose its deep convection and become a remnant low by Wednesday night. The latest forecast is essentially an update of the previous official intensity forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 18.7N 117.7W   35 KT  40 MPH - Tropical Storm (WNW Isla Clarión, MX)
 12H  24/0000Z 19.4N 118.3W   35 KT  40 MPH - Tropical Storm (WNW Isla Clarión, MX)
 24H  24/1200Z 20.3N 119.2W   30 KT  35 MPH - Tropical Storm (WNW Isla Clarión, MX)
 36H  25/0000Z 20.9N 120.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  25/1200Z 21.5N 121.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 AM PDT Tue Jul 23, 2019

Deep convection has become stronger and closer to the center of the cyclone during the past several hours. While the circulation is still elongated, it has become better defined, with the latest ASCAT pass at 0440 UTC showing 30-35 kt winds in the southern quadrant. Since TAFB, ADT and SATCON have the current intensity as a tropical storm, plus the recent increase in organization, the current wind speed has been set to 35 kt.

Dalila is probably near peak intensity. Since SSTs drop off later today, along with a continuation of moderate northerly shear, weakening should begin on Wednesday. In a couple of days, SSTs near 24C, dry air aloft, and a more stable atmosphere should contribute to Dalila losing deep convection, thus becoming a remnant low. This is the solution provided by much of the guidance, and the latest NHC intensity prediction is close to the previous one.

The cyclone has been moving erratically at 330/6 due to the center trying to reform near the strong convection to the south. A mid-level ridge over the southwestern United States should provide similar steering during the next day or so, causing a motion generally toward the northwest by Wednesday. As Dalila weakens, it will likely turn more to the west-northwest on Thursday within the low-level flow. Similar to the past few cycles, model guidance is continuing to shift westward, and the official forecast follows that trend, not terribly far from the eastern Pacific track consensus model TVCE.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0900Z 18.0N 117.3W   35 KT  40 MPH - Tropical Storm (WNW Isla Clarión, MX)
 12H  23/1800Z 18.8N 117.8W   35 KT  40 MPH - Tropical Storm (WNW Isla Clarión, MX)
 24H  24/0600Z 19.8N 118.6W   30 KT  35 MPH - Tropical Storm (WNW Isla Clarión, MX)
 36H  24/1800Z 20.6N 119.5W   30 KT  35 MPH - Tropical Storm (WNW Isla Clarión, MX)
 48H  25/0600Z 21.3N 120.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/0600Z 22.3N 123.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  27/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Mon Jul 22,  2019

A recent satellite microwave pass indicates that the depression has not gotten any better organized this morning. It appears that northeasterly shear is keeping much of the convection displaced to the west of the center of circulation. Both the latest TAFB Dvorak satellite intensity estimate and UW-CIMMS objective intensity estimate indicate that the system remains a 30-kt depression.

The initial motion of the depression is 355/08 kt. Model guidance is in good agreement on a continuation of this general motion for the next 36-48 hours as the depression is steered between a weak mid-level trough to its west, and a building mid-level ridge to its northeast. After 48 hours, the system should begin to weaken and turn toward the northwest as it becomes steered by the lower-level flow. The latest NHC forecast track is very near the previous official forecast and is near the track guidance consensus.Tropical Storm Dalila Forming_Wind_Speeds_0500 Hours July 22 2019

Although convection has increased this morning, the shear is preventing the inner core of the depression from becoming better established. This shear is forecast to remain in the 15-20 kt range for the next 48 hours which should continue to prevent any significant intensification during that time frame. Since the other environmental parameters are somewhat favorable for intensification during the next day or so, the depression will likely become a minimal tropical storm later today or tonight. After 48 hours, the system will move over waters below 26 C and into a stable atmospheric environment which should induce steady weakening. By 72 hours, the system is expected to become a remnant low, with dissipation likely by 120 hours. The official intensity forecast is close to the previous NHC forecast, and is near the more reliable intensity guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 15.9N 116.3W   30 KT  35 MPH - Tropical Depression (WSW Acapulco, MX)
 12H  23/0000Z 17.0N 116.5W   35 KT  40 MPH - Tropical Storm  (WSW Acapulco, MX)
 24H  23/1200Z 18.5N 116.8W   35 KT  40 MPH - Tropical Storm  (WNW Isla Clarión, MX)
 36H  24/0000Z 19.8N 117.3W   35 KT  40 MPH - Tropical Storm  (WNW Isla Clarión, MX)
 48H  24/1200Z 20.8N 118.0W   35 KT  40 MPH - Tropical Storm  (WSW Cabo San Lucas, MX)
 72H  25/1200Z 22.3N 120.0W   25 KT  30 MPH - POST-TROP/REMNT LOW  (WSW Cabo San Lucas, MX)
 96H  26/1200Z 23.5N 122.5W   20 KT  25 MPH - POST-TROP/REMNT LOW  (WSW Cabo San Lucas, MX)
120H  27/1200Z 24.0N 125.0W   20 KT  25 MPH - DISSIPATED  (WSW Puerto Cortés, MX)

NWS National Hurricane Center Miami FL 200 AM PDT Mon Jul 22, 2019

The area of disturbed weather and low-pressure system located about 600 nmi southwest of Baja California Sur that the NHC has been monitoring for the past several days has finally developed a sufficient inner-core wind field and enough organized deep convection to be classified as a tropical cyclone. The initial intensity is set at 30 kt based on two ASCAT passes between 0430-0530Z that showed 30-31 kt wind vectors in the western quadrant, which corresponds well with the latest TAFB Dvorak satellite intensity estimate of T2.0/30 kt from TAFB.

The initial motion estimate is an uncertain 360/08 kt due to the lack of a well-defined center until recently. However, the NHC model guidance is in surprisingly good agreement on the cyclone moving northward for the next 36-48 hours around the eastern periphery of a broad mid-level low/trough located to the west of the depression. By 72 h and continuing through 120 h, the cyclone is forecast to move northwestward as a weakening remnant low-pressure system. The NHC forecast track lies close to a blend of the various consensus models, and is about midway between the GFS and ECMWF model solutions that bound on the eastern and western fringes, respectively, of the track guidance envelope.

Modest north to northeasterly vertical wind shear and occasional intrusions of dry air are expected to hinder development and strengthening for the next 48 hours or so. By late on day 2 and especially by day 3, the cyclone will be moving over sub-26 deg C sea-surface temperatures, which will induce at least steady weakening despite decreasing vertical wind shear conditions during that time. The official intensity forecast is similar to but slightly higher higher than the IVCN and HCCA intensity consensus models, with the latter guidance calling for no strengthening.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 15.0N 116.2W   30 KT  35 MPH - (WSW Acapulco, MX)
 12H  22/1800Z 16.3N 116.3W   30 KT  35 MPH - (WSW Acapulco, MX)
 24H  23/0600Z 17.9N 116.6W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  23/1800Z 19.2N 117.0W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 48H  24/0600Z 20.4N 117.7W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 72H  25/0600Z 22.0N 119.6W   25 KT  30 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)
 96H  26/0600Z 23.2N 122.0W   20 KT  25 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)
120H  27/0600Z 24.6N 124.5W   20 KT  25 MPH...POST-TROP/REMNT LOW - (WSW Cabo San Lucas, MX)

 

NWS National Hurricane Center Miami FL 500 PM PDT Sun Jul 21, 2019

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

Satellite data indicate that the circulation of a low-pressure area located about 800 miles south-southwest of the southern tip of the Baja California peninsula remains elongated. However, the associated showers and thunderstorms are showing signs of organization, and a tropical depression or a tropical storm is expected to form during the next day or so. This system is forecast to move generally northwestward and remain well offshore of the coast of Mexico.

* Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Jul 21, 2019

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

Showers and thunderstorms have increased a little today in association with a broad area of low pressure located several hundred miles south-southwest of the southern tip of the Baja California peninsula. This system appears to lack a well-defined center. However, conditions are favorable for a tropical depression or a tropical storm to form during the next day or so as it moves generally northwestward at around 10 mph, remaining well offshore the coast of Mexico.

* Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Jul 21, 2019

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

Showers and thunderstorms located several hundred miles south-southwest of the southern tip of the Baja California peninsula are associated with an elongated area of low pressure. The disturbance is gradually becoming better defined, and a tropical depression or a tropical storm is expected to form during the next day or so. The disturbance is forecast to move generally northwestward at around 10 mph, remaining well offshore the coast of Mexico.

* Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Sat Jul 20, 2019,

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

Satellite imagery indicates that a low-pressure system located several hundred miles south-southwest of the southern tip of the Baja California peninsula is gradually becoming better defined. Thunderstorm activity has been steadily increasing and becoming better organized, and a tropical depression or a tropical storm is expected to form during the next day or so. The disturbance is forecast to move generally northwestward at around 10 mph, remaining well offshore the coast of Mexico.

* Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sat Jul 20, 2019

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

Satellite imagery indicates that a broad and elongated low-pressure area has formed in association with the disturbed weather located several hundred miles south-southwest of the southern tip of the Baja California peninsula. Environmental conditions are expected to be conducive for additional development of this system, and a tropical depression is likely to form within the next day or two. This disturbance is forecast to move generally northwestward at around 10 mph away from 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 500 AM PDT Sat Jul 20 2019

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

1. A large area of disturbed weather is located several hundred miles south-southwest of the southern tip of the Baja California
peninsula. Environmental conditions are expected to be conducive for development, and a tropical depression is likely to form within the next few days as it moves west-northwestward away from 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 Fri Jul 19 2019

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

1. A large area of disturbed weather located several hundred miles southwest of the southwestern coast of Mexico is associated with
a tropical wave. Environmental conditions are expected to be conducive for development during the next few days, and a tropical depression is likely to form early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph,
away from the coast of Mexico.

* 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 Fri Jul 19, 2019

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

A large area of disturbed weather located several hundred miles southwest of the southwestern coast of Mexico is associated with
a tropical wave. Environmental conditions appear to be conducive for gradual development during the next few days, and a tropical depression is likely to form early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…high...70 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Jul 19, 2019

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

An area of disturbed weather located several hundred miles southwest of the southwestern coast of Mexico is associated with a tropical wave. Environmental conditions appear to be conducive for gradual development, and a tropical depression could form early next week before the system reaches cooler waters. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Jul 19, 2019

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

An area of disturbed weather located several hundred miles south of Manzanillo, Mexico is associated with a tropical wave. Environmental conditions could become a little more conducive for gradual development, and a tropical depression could form early next week before the system reaches cooler waters. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Thu Jul 18, 2019

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

Shower activity associated with a tropical wave located several hundred miles south of Manzanillo, Mexico continues to be limited at this time. Environmental conditions could become a little more more conducive for gradual development, and a tropical depression could form early next week before the system reaches cooler waters. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* 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 Thu Jul 18 2019

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

Shower activity associated with a tropical wave located several hundred miles south of Manzanillo, Mexico is very limited at this time. Environmental conditions could become a little more more conducive for gradual development, and a tropical depression could form early next week before the system reaches cooler waters. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Jul 18, 2019

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

A tropical wave located several hundred miles south of Manzanillo, Mexico continues to produce disorganized showers and thunderstorms. Environmental conditions are forecast to become more conducive for gradual development during the weekend, and a tropical depression could form early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, away from the coast of Mexico.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium...50 percent

NWS National Hurricane Center Miami FL 500 AM PDT Thu Jul 18, 2019

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

A tropical wave located a few hundred miles south-southwest of Acapulco is producing disorganized showers and thunderstorms. Environmental conditions are forecast to become more conducive for gradual development, and a tropical depression could form early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, well south of the coast of Mexico.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Wed Jul 17, 2019

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

1. A tropical wave located a few hundred miles south of Acapulco is producing disorganized showers and thunderstorms. Environmental conditions are forecast to become more conducive for gradual development, and a tropical depression could form over the weekend or early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, well south of the coast of 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 PM PDT Wed Jul 17, 2019

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

A tropical wave located a few hundred miles south of Acapulco is producing disorganized showers and thunderstorms. Environmental conditions are forecast to become more conducive for gradual development late this week, and a tropical depression could form over the weekend or early next week. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, well south of the coast of Mexico.

* 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 Jul 16, 2019

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

1. A tropical wave located a couple of hundred miles south of Guatemala continues to produce disorganized cloudiness and showers. Environmental conditions are forecast to become conducive for gradual development later this week, and a tropical depression could form this weekend. This disturbance is forecast to move westward to
west-northwestward at 10 to 15 mph, well south of the coast of Mexico.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Tue Jul 16,  2019

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

A tropical wave located a couple of hundred miles south of Guatemala is producing disorganized cloudiness and showers. Environmental conditions are forecast to become conducive for gradual development later this week, and a tropical depression could form by the weekend. This disturbance is forecast to move westward to west-northwestward at 10 to 15 mph, well south of the coast of 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 Mon Jul 15, 2019

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

1. A westward-moving tropical wave has emerged off the coasts of Costa Rica and Nicaragua this morning. An area of low pressure is likely to form in association with this disturbance during the next few days several hundred miles south of the southern coast of Mexico. Conditions appear favorable for the gradual development of this system by late week and over the weekend while it moves westward to west-northwestward at 10 to 15 mph.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

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