Tropical Storm Ilena

Tropical Storm Ilena Joins Hurricane John 0900 Hours August 7 2018
Tropical Storm Ilena Joins Hurricane John 0900 Hours August 7 2018
Tropical Storm Ilena Joins Hurricane John August 7 2018
Tropical Storm Ilena Joins Hurricane John August 7 2018

NWS National Hurricane Center Miami FL 900 AM MDT Tue Aug 07 2018

Early morning GOES-16 one-minute satellite imagery confirms that the small circulation of Ileana has dissipated within the northern portion of Hurricane John’s larger circulation. As a result, this is the final NHC advisory on Ileana. The remnants of the tropical cyclone are likely producing an area of tropical-storm-force winds that should gradually decrease in intensity as it rotates around the northern and northwestern portion of John during the next few hours. Hurricane John

NWS National Hurricane Center Miami FL 400 PM CDT Mon Aug 06 2018

There have been significant changes to the forecast reasoning for Ileana. Recent satellite imagery suggest that the system is being adversely affected by the large circulation of John much sooner than anticipated. In fact, Ileana is looking more like an outer band of John at this time. Nonetheless, a recent ASCAT overpass indicated that Ileana is still a separate system to the east-northeast of John and continues to support a current intensity of 55 kt.

However given the evolution of Ileana today, the previous NHC short-term intensity forecast is reversed. Ileana is no longer predicted to become a hurricane, and the tropical cyclone is likely to dissipate or become absorbed by John’s circulation in 24-36 hours. It should be noted that some models, such as the HWRF, GFS, and ECMWF depict Ileana’s demise even sooner than that.

Since the cloud pattern of Ileana has become rather disorganized, it is difficult to track a center and the initial motion is an uncertain 305/15 kt. The cyclone should move between a mid-level ridge and the circulation of John until dissipation. The official track forecast is a little left of the previous one, but a little to the right of the track model consensus. The 34- and 50-kt wind radii have been adjusted based on the scatterometer data.

The hurricane watch for the southwest coast of Mexico is discontinued. The tropical storm watch for the extreme southern Baja California peninsula is also discontinued for Ileana, but a watch for this same general area may soon be required for John.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 17.0N 103.3W   55 KT  65 MPH - (SE of Lázaro Cárdenas, Mx)
 12H  07/0600Z 18.2N 105.8W   55 KT  65 MPH - (SE of Manzanillo, Mx)
 24H  07/1800Z 19.5N 109.0W   45 KT  50 MPH - (SE of Puerto Vallarta, Mx)
 36H  08/0600Z...DISSIPATED

National Hurricane Center Miami FL 1000 AM CDT Mon Aug 06 2018

Ileana continues to produce very deep convection near its center, with cloud tops colder than -80 deg C. Microwave imagery and the Acapulco radar have shown some eyewall structure, at least at mid-levels. Although conventional Dvorak classifications from TAFB and SAB provided intensity estimates of only 45 kt, the advisory intensity is kept at 55 kt in better agreement with SATCON estimates from UW-CIMSS.

Since Ileana will be in a moist, low-shear, and warm water environment, the system is likely to strengthen into a hurricane within 12 hours or so, with some additional intensification through Tuesday morning. Thereafter, the influence of the much larger circulation of John to the southwest is expected to begin having an adverse effect on Ileana. The system should begin weakening later on Tuesday, and dissipate or become absorbed by John on Wednesday. This is the scenario that is depicted by the ECMWF and GFS global model guidance.

Ileana continues to move briskly toward the northwest or about 310/15 kt. The tropical cyclone is expected to move between a mid-level ridge and the circulation of John for the next couple of days. The official track forecast is a little to the left of the previous one but a little north of the latest multi-model consensus. No changes to the watches and warnings are required at this time. Although the core of strongest winds is forecast to remain offshore of the coast of southwestern Mexico, only a slight deviation to the right of track could bring stronger winds onshore, particularly in the area where the hurricane watch has been posted.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 16.3N 101.9W   55 KT  65 MPH (SW of Zihuatanejo, Mx)
 12H  07/0000Z 17.8N 104.2W   65 KT  75 MPH (SW of Colola, Mx)
 24H  07/1200Z 19.3N 107.2W   70 KT  80 MPH (SW of Tomatlán, Mx)
 36H  08/0000Z 20.5N 109.5W   60 KT  70 MPH (W of Puerto Vallarta, Mx)
 48H  08/1200Z 21.5N 111.6W   50 KT  60 MPH (SW of Cabo San Lucas, Mx)
 72H  09/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 700 PM CDT Sun Aug 05 2018

At 700 PM CDT (0000 UTC), the center of Tropical Storm Ileana was located near latitude 13.9 North, longitude 98.9 West. Ileana is moving toward the west-northwest near 12 mph (19 km/h). A turn to the northwest is forecast tonight with an additional increase in forward speed expected over the next few days. On the forecast track, the center of Ileana should move parallel to, and offshore of, the coast of southwestern Mexico through Tuesday. Maximum sustained winds have increased to near 50 mph (85 km/h) with higher gusts. Some additional strengthening is expected through Monday, but the storm is forecast to dissipate by Wednesday as it comes under the influence of a larger cyclone to its west and southwest.

Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1001 mb (29.56 inches).

WIND: Tropical storm conditions are possible within the watch area late Monday and Tuesday.

RAINFALL: Ileana is expected to produce total rain accumulations of 2 to 4 inches over coastal sections of the Mexican states of Guerrero, Michoacan, Colima, and Jalisco, with possible isolated maximum amounts of 6 inches through Tuesday night. These rains may cause flash flooding.

SURF: Swells generated by Ileana will be affecting portions of the coast of southwestern Mexico during the next couple of days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 400 PM CDT Sun Aug 05 2018

The cyclone has continued to become better organized today, with a fairly symmetrical shape on geostationary imagery. Data from a recent ASCAT overpass showed that the center was embedded about in the middle of a small CDO-like feature. The scatterometer data indicated maximum winds of 35-40 kt, and Dvorak classifications from TAFB and SAB gave intensity estimates of 35 kt and 45 kt, respectively. Blending these various estimates yields a current intensity of about 40 kt, and the tropical cyclone is thus being named. Since the system should be in a warm water and low shear environment for the next couple of days, some additional strengthening is forecast. However a strengthening cyclone is situated not far to the west of Ileana. This larger system is forecast by the ECMWF and GFS models to become the dominant cyclone in a few days, and cause the tropical storm to dissipate near the northern side of the larger circulation. That is the scenario shown by the official intensity forecast.

There is more confidence in the center position than there was earlier today, and the estimated initial motion is west-northwestward or 285/9 kt. Over the next couple of days, Ileana is likely to move between a mid-level ridge to its north and northeast and the larger cyclonic circulation to its west and southwest. The official track forecast is on the southern side of the track guidance envelope. It is also very close to the latest HCCA forecast track.

Interests along the coast of southern and southwestern Mexico should monitor the progress of this system, given the uncertainties in the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 13.6N  98.1W   40 KT  45 MPH - (SW of Puerto Escondido, Mx)
 12H  06/0600Z 14.5N 100.0W   45 KT  50 MPH - (SW of Acapulco, Mx)
 24H  06/1800Z 16.2N 102.3W   50 KT  60 MPH - (SW of Zihuatanejo, Mx)
 36H  07/0600Z 17.9N 104.6W   50 KT  60 MPH - (SW of Colola, Mx)
 48H  07/1800Z 19.2N 106.7W   45 KT  50 MPH - (NW of San Patricio, Mx)
 72H  08/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1000 AM CDT Sun Aug 05 2018

Latest visible satellite images indicate that the tropical cyclone is gradually becoming better organized. The center is estimated to be on the northern side of a small circular area of deep convection, with a developing band of convection over the southern semicircle of the circulation. The initial intensity is set at 30 kt in agreement with the latest Dvorak estimates from both TAFB and SAB.

Since the center is still not easy to locate, the initial motion is a rather uncertain 290/10 kt. The primary steering mechanisms for the system are a mid-level ridge to the north and a developing cyclone to the west. It is not clear just how much interaction will occur between the two cyclones, and it is likely that some of the model vortex tracks are not representative in the 2-3 day time frame. The forecast track is somewhat north of the previous one but near the southern side of the guidance envelope. This is close to the latest HFIP Corrected Consensus Approach, HCCA, track.

The GFS and ECMWF global model predictions indicate that the circulation to the west of Eleven-E will become dominant. In fact, the GFS indicates that this circulation will absorb the tropical cyclone within a day or so. The ECMWF indicates that this absorption will occur several days later, and the official forecast calls for dissipation in 3-4 days. If the western circulation does not become the dominant system, then Eleven-E could strengthen more than indicated here, as shown by some of the other guidance.

Interest along the coast of southern and southwestern Mexico should monitor the progress of this system, given the uncertainties in the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 13.5N  97.3W   30 KT  35 MPH - (S of Puerto Escondido, Mx)
 12H  06/0000Z 14.1N  98.8W   35 KT  40 MPH - (SW of Puerto Escondido, Mx)
 24H  06/1200Z 15.3N 100.8W   35 KT  40 MPH - (SW of Acapulco, Mx)
 36H  07/0000Z 16.9N 103.8W   40 KT  45 MPH - (SW of Zihuatanejo, Mx)
 48H  07/1200Z 18.3N 106.5W   45 KT  50 MPH - (SW of Manzanillo, Mx)
 72H  08/1200Z 20.5N 112.0W   35 KT  40 MPH - (SW of Cabo San Lucas, Mx)
 96H  09/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 400 PM CDT Sat Aug 04 2018 E

Tropical Depression Eleven- – Discussion Number Satellite images indicate that the disturbance located over the far eastern Pacific has become significantly better organized throughout the day, with the formation of a well-defined low pressure center and deep convection organized in a distinct curved band. Based on these criteria, the system is being designated as a tropical depression, and the initial intensity is set at 25 kt in accordance with Dvorak estimates from TAFB and SAB.

Because the system has congealed so quickly, the initial motion is uncertain but estimated to be 285/11 kt. The cyclone’s future motion will ultimately be dictated by a large mid-tropospheric ridge to its north and its proximity to another disturbance located about 450 n mi to the west. A west-northwestward motion at a nearly constant speed is expected during the next 2-3 days due to the ridge. After that time, the cyclone could begin to slingshot around the northern side of the larger weather system to its west. Many of the track models are not handling the depression very well; the GFS barely depicts a surface low from the get-go, and the HWRF does not appear to be accounting sufficiently for the possibility of binary interaction. As a result, the NHC official track forecast matches the consensus of the ECMWF and UKMET, the only two models which appear to have a decent grasp on the situation.

Although the depression will be moving over very warm waters of 29-30 degrees Celsius over the next 2-3 days, the upper-level wind environment may not be ideal due to possible outflow from the larger disturbance to the west. As a result, the official intensity forecast is not too aggressive and is essentially close to the ICON intensity consensus. Even though the ECMWF and UKMET were used for the track forecast, the two models disagree on the cyclone’s ultimate demise. The ECMWF has the system absorbed by the other disturbance by day 4, while the UKMET keeps it distinct and holds it just beyond the forecast period. As a compromise, the official forecast shows dissipation or absorption by day 5, but the confidence in this forecast is low.

Based on the forecast, tropical-storm-force winds are expected to remain offshore the coast of Mexico. However, only a slight deviation in the forecast track or an increase in size could bring those winds closer to the coast, and interests along the southern and southwestern coast of Mexico should monitor the progress of the depression.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 12.4N  95.0W   25 KT  30 MPH
 12H  05/0600Z 12.9N  96.4W   30 KT  35 MPH
 24H  05/1800Z 13.6N  98.3W   35 KT  40 MPH - Tropical Storm
 36H  06/0600Z 14.3N 100.2W   40 KT  45 MPH - Tropical Storm
 48H  06/1800Z 15.3N 102.4W   45 KT  50 MPH - Tropical Storm
 72H  07/1800Z 18.3N 107.8W   50 KT  60 MPH - Tropical Storm
 96H  08/1800Z 20.0N 114.0W   45 KT  50 MPH - Tropical Storm (SW of Cabo San Lucas, Mx)
120H  09/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Aug 4 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located over the far southwestern part of the basin.

Satellite data indicate that a broad low pressure area has formed several hundred miles south-southwest of Acapulco, Mexico. Environmental conditions are conducive for significant development, and a tropical depression or tropical storm is expected to form tonight or tomorrow while the system moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…near 100 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Aug 4 2018

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

Showers and thunderstorms associated with an area of low pressure centered about 825 miles south-southwest of the southern tip of the Baja California peninsula continue to show signs of organization. Environmental conditions are likely to support additional development, and a tropical depression is expected to form by early next week as the system moves slowly westward. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high...90 percent

NWS National Hurricane Center Miami FL 1100 PM PDT Fri Aug 3 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

1. Showers and thunderstorms associated with an area of low pressure centered about 800 miles south-southwest of the southern tip of the Baja California peninsula have changed little in organization over the past several hours. Environmental conditions are expected to support additional development and a tropical depression is likely to form by early next week as the system moves slowly westward.
* Formation chance through 48 hours…medium…60 percent.
* Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Aug 3 2018

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

The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

1. Satellite imagery indicates that shower activity associated with a low pressure area centered about 750 miles south-southwest of the southern tip of Baja California is becoming better organized. Environmental conditions appear conducive for further development, and a tropical depression is likely to form over the weekend or
early next week. The low is forecast to move slowly westward over the next few days.
* Formation chance through 48 hours…medium…60 percent.
* Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Aug 3 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

A large area of disturbed weather centered several hundred miles southwest of the Gulf of Tehuantepec remains poorly organized. However, environmental conditions are expected to be conducive for development during the next several days, and a tropical depression or tropical storm is expected to form by early next week while it moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Aug 3 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located well southwest of Baja California Sur.

A tropical wave is producing disorganized showers and thunderstorms several hundred miles south-southwest of Manzanillo, Mexico. Environmental conditions appear marginally conducive for gradual development of this system during the next few days as it moves slowly west-northwestward or northwestward. By early next week, proximity to another low pressure system could limit further development of this disturbance. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…50 percent. 2. An area of disturbed weather centered several hundred miles south- southwest of the Gulf of Tehuantepec remains poorly organized. However, environmental conditions are expected to be conducive for development during the next several days, and a tropical depression is likely to form by early next week while it moves west- northwestward off the coast of Mexico. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 1700 AM PDT Thu Aug 2 2018

An area of disturbed weather centered several hundred miles south- southwest of the Gulf of Tehuantepec remains poorly organized. However, environmental conditions are expected to be conducive for development during the next several days, and a tropical depression is likely to form on Sunday or Monday while it moves west- northwestward off the coast of Mexico. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Aug 2 2018

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

The National Hurricane Center is issuing advisories on recently upgraded Hurricane Hector, located well southwest of Baja California Sur.

An area of disturbed weather centered several hundred miles south of the Gulf of Tehuantepec shows no signs of organization. However, environmental conditions are expected to be conducive for significant development for the next several days, and a tropical depression is likely to form on Sunday or Monday while it moves west-northwestward off the coast of Mexico.

* Formation chance through 48 hours…low…10 percent.
* Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Aug 2 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on strengthening Tropical Storm Hector, located well southwest of the southern tip of the Baja California Peninsula.

An area of disturbed weather has formed several hundred miles south of the Gulf of Tehuantepec. Environmental conditions are expected to be conducive for development, and a tropical depression is likely to form early next week while it moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Wed Aug 1 2018

An area of low pressure is forecast to form several hundred miles south or southwest of the southern coast of Mexico late this week. Environmental conditions are expected to be conducive for gradual development of this system over the weekend, and a tropical depression could form early next week while it moves west-northwestward off the coast of Mexico. * 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 Aug 1 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Hector, located well southwest of the southern tip of the Baja California Peninsula.

1. An area of low pressure is forecast to form several hundred miles south or southwest of the Gulf of Tehuantepec late this week. Environmental conditions are expected to be conducive for gradual development of this system over the weekend, and a tropical depression could form early next week while it moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

If this storm is named, it will be Tropical Storm Ilena.

NWS National Hurricane Center Miami FL 500 AM PDT Wed Aug 1 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Hector, located well southwest of the southern tip of the Baja California Peninsula.

1. An area of low pressure is forecast to form several hundred miles south or southwest of the Gulf of Tehuantepec late this week. Environmental conditions are expected to be conducive for gradual development of this system over the weekend, and a tropical depression could form early next week while it moves west-northwestward off the coast of Mexico.

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

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