Tropical Storm Kirk

Tropical Storm Kirk Track 1700 Hours September 28 2018
Tropical Storm Kirk Track 1700 Hours September 28 2018

NWS National Hurricane Center Miami FL 500 PM AST Fri Sep 28 2018

Tropical Storm Kirk (see 12 videos below) is barely meeting the criteria for a tropical cyclone. The small low-level center is still exposed well to the west of most of the deep convection. The last fix from the earlier Air Force Reserve Hurricane Hunter mission found that the cyclone was still closed, but the maximum winds had decreased to near 35 kt. Since it seems likely that winds of this magnitude are still occuring in the convection to the east of Kirk, the system is maintained as a tropical storm for this advisory. Another reconnaissance mission is scheduled for tonight, and it should give a better estimate of the intensity of Kirk, and if the cyclone still has a well-defined surface circulation.

No significant changes have been made to the track or intensity forecasts. Kirk is expected to move generally west-northwestward to northwestward over the next 12 hours or so while weakening due to the continued effects of strong westerly wind shear. By tomorrow morning, the cyclone will likely have degenerated into a trough of low pressure. Even though Kirk is weakening, heavy rains are expected over St Croix and eastern Puerto Rico during the next day or two while Kirk or its remnants pass to the south of those islands.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 14.7N  64.7W   35 KT  40 MPH - Tropical Storm (ESE Saint-Pierre, Martinique)
 12H  29/0600Z 15.3N  66.2W   30 KT  35 MPH - Tropical Storm (ESE Roseau, Dominica)
 24H  29/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Fri Sep 28 2018

Tropical Storm Kirk  has become less organized since the last advisory, with satellite imagery showing that the low-level center is now exposed well to the west-northwest of the remaining deep convection. Reports from an Air Force Reserve Hurricane Hurricane Hunter aircraft indicate that the winds have decreased to near 40 kt and that the central pressure has risen to near 1007 mb. The aircraft also reports that the circulation is losing definition in the southwestern quadrant. Kirk should continue to weaken due to the effects of 30 kt of westerly vertical shear, and the NHC forecast continues to call for dissipation just after 24 h. As noted in the previous discussion, there is a chance dissipation could occur earlier than currently forecast.

The center has jogged back to the west-northwest during the past few hours, which results in an uncertain initial motion of 285/11. Kirk should move generally west-northwestward on the south side of the subtropical ridge until dissipation.

Even though Kirk is weakening and moving away from the Lesser Antilles, the associated gusty winds and rains should continue affecting the islands today.

FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 13.8N  63.6W   40 KT  45 MPH - Tropical Storm (ESE Fond Doux, St. Lucia)
 12H  29/0000Z 14.2N  65.3W   35 KT  40 MPH - Tropical Storm (WNW Castries, St. Lucia )
 24H  29/1200Z 14.8N  67.6W   25 KT  30 MPH - Subtropical Storm (ESE Saint-Pierre, Martinique,)
 36H  30/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM AST Thu Sep 27 2018

DISCUSSION AND OUTLOOK

At 800 PM AST (0000 UTC), the center of Tropical Storm Kirk was located by an Air Force Reserve Hurricane Hunter aircraft just east of St. Lucia near latitude 13.9 North, longitude 60.7 West. Kirk is moving toward the west-northwest near 14 mph (22 km/h). A west- northwestward to westward motion is expected over the next couple of days. On the forecast track, the center of Kirk will move across the Lesser Antilles within the Tropical Storm Warning area during the next several hours.

Maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Little change in strength is expected while the center of Kirk moves through the Lesser Antilles. Gradual weakening is anticipated during the next couple of days while the system moves over the eastern Caribbean Sea. Kirk is forecast to become a tropical depression Friday night, and degenerate into a trough of low pressure by Sunday.

Tropical-storm-force winds extend outward up to 140 miles (220 km) primarily to the east of the center.

The minimum central pressure based on data from the aircraft is 1002 mb (29.59 inches).

HAZARDS AFFECTING LAND

WIND: Tropical storm conditions are expected to begin in portions of the warning area during the next few hours. Tropical storm conditions are possible within the watch area overnight. Locally higher winds are possible atop and on the windward sides of hills and mountains.

RAINFALL: Kirk is expected to produce total rainfall of 4 to 6 inches across the northern Windward and southern Leeward Islands with isolated maximum totals up to 10 inches across Martinique and Dominica. These rains may produce life-threatening flash floods and mudslides. Across Saint Croix and eastern Puerto Rico, Kirk is expected to bring 2 to 4 inches with isolated maximum totals of 6 inches by Friday and Saturday.

NWS National Hurricane Center Miami FL 500 PM AST Thu Sep 27 2018

Tropical Storm Kirk  remains a sheared tropical cyclone with the exposed low-level center located to the west of the main convective mass. There has been some redevelopment of deep convection just northeast of the center this afternoon, but much of the convection is located well east and southeast of the center. Despite the satellite presentation, the Air Force Hurricane Hunter aircraft investigating Kirk through early this afternoon continued to find winds to support an initial intensity of 45 kt. Another reconnaissance aircraft mission is scheduled to fly into the storm late this afternoon and evening.

The strong westerly shear that is currently affecting the tropical cyclone is forecast to increase over the next day or so, and Kirk is expected to weaken as the low- and mid-level centers decouple even further. Kirk is forecast to weaken to a tropical depression within 36 hours, and is likely to become an open trough in 2 to 3 days when the system reaches the central Caribbean Sea. The NHC intensity forecast is in good agreement with the various intensity aids, and the global models which show weakening and dissipation of the system within 72 hours.

Kirk is moving west-northwestward or 290 degrees at 12 kt. A low- to mid-level ridge located over the southwestern Atlantic is expected to steer Kirk west-northwestward to westward during the next couple of days. The updated NHC track forecast is near the middle of the tightly clustered guidance, and is essentially an update of the previous advisory.

Interests in the Lesser Antilles should bear in mind that, although Kirk has become less organized over the past 24 hours, heavy rainfall and winds are still occurring over the eastern portion of the circulation. These winds and rains are still likely to spread westward over the islands in the Tropical Storm Warning area later this evening through early Friday. Higher winds are especially likely over elevated terrain.

FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 14.2N  60.2W   45 KT  50 MPH - Tropical Storm (ESE Sainte-Anne, Martinique)
 12H  28/0600Z 14.6N  62.2W   40 KT  45 MPH - Tropical Storm (E Fort-de-France, Martinique)
 24H  28/1800Z 15.3N  64.5W   35 KT  40 MPH - Tropical Storm (WSW Portsmouth, Dominica)
 36H  29/0600Z 15.8N  66.8W   30 KT  35 MPH - Tropical Storm (WSW Ponce, Puerto Rico)
 48H  29/1800Z 16.1N  69.0W   25 KT  30 MPH - Tropical Storm (ESE Santo Domingo, Dominican Republic )
 72H  30/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 PM AST Thu Sep 27 2018

TROPICAL STORM KIRK  ABOUT TO MOVE THROUGH THE LESSER ANTILLES

INFORMATION:

LOCATION…14.0N 59.9W

ABOUT 60 MI…100 KM NNW OF BARBADOS

ABOUT 90 MI…140 KM ESE OF MARTINIQUE

MAXIMUM SUSTAINED WINDS…50 MPH…85 KM/H

PRESENT MOVEMENT…WNW OR 290 DEGREES AT 14 MPH…22 KM/H

MINIMUM CENTRAL PRESSURE…1000 MB…29.53 INCHES

NWS National Hurricane Center Miami FL 1100 AM AST Thu Sep 27 2018

Tropical Storm Kirk –  Increasing vertical shear is having a notable influence on the structure of Kirk, as visible satellite imagery shows that the low-level center of the cyclone is now exposed to the west of the main area of deep convection. Nonetheless, the Air Force Hurricane Hunters still found strong winds in that convection. In fact, based on SFMR and flight-level winds from the Hurricane Hunters, the advisory intensity of 45 kt may be a conservative estimate. With the increasing vertical decoupling of the vortex and even stronger shear associated with upper-level westerlies over the Caribbean Sea, weakening is likely over the next couple of days. Kirk should degenerate into a remnant low in 2 to 3 days, if not sooner. The official forecast is close to the multi-model intensity consensus, IVCN.

The storm continues moving west-northwestward, with a current motion estimate of 285/13 kt. A mid-level high pressure area just to the east of Florida is likely to steer Kirk on a west-northwestward to westward course for the next few days. Some further slowing of forward speed is expected as the high weakens slightly. The NHC track forecast is very close to the latest HFIP corrected consensus prediction.

Interests in the Lesser Antilles should bear in mind that, although Kirk is becoming disorganized, strong winds are still occurring over the eastern portion of the circulation. These winds are still likely to spread westward over the islands in the Tropical Storm Warning area later today. Higher winds are especially likely over elevated terrain.

FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 13.8N  59.3W   45 KT  50 MPH - Tropical Storm (ESE Mon Repos, Saint Lucia)
 12H  28/0000Z 14.3N  61.0W   40 KT  45 MPH - Tropical Storm (ESE Le Diamant, Martinique)
 24H  28/1200Z 14.9N  63.2W   35 KT  40 MPH - Tropical Storm (WSW Roseau, Dominica)
 36H  29/0000Z 15.5N  65.4W   30 KT  35 MPH - Tropical Storm (WSW Portsmouth, Dominica)
 48H  29/1200Z 15.9N  67.7W   25 KT  30 MPH - Tropical Storm (WSW Ponce, Puerto Rico)
 72H  30/1200Z 16.0N  72.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  01/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM AST Thu Sep 27 2018

Tropical Storm Kirk   has not changed much overnight. Although the storm is producing a large area of deep convection, the cloud pattern is not very well organized with the center located near the southwestern edge of the thunderstorms. This asymmetric cloud pattern is due to about 20 kt of southwesterly shear. The Air Force Hurricane Hunters passed through the northeastern quadrant of Kirk a few hours ago and found winds to support the same intensity of 45 kt. In addition, quality control of a ship report that came in around the same time also supports that intensity. Another Air Force plane is scheduled to investigate Kirk later this morning.

A large fetch of strong upper-level westerly or southwesterly winds are over the entire Caribbean Sea, and Kirk will be moving into these conditions during the next few days. These very hostile winds aloft should cause Kirk to steadily weaken, decouple, and ultimately dissipate in 3 or 4 days. The GFS and ECMWF models suggest that dissipation could occur even sooner. The intensity models are in good agreement, and the NHC forecast is the same as the previous one.

Center fixes from the Air Force reconnaissance aircraft indicate that Kirk is moving west-northwestward at 14 kt. A continued west-northwest motion but at a slower pace is expected during the next few days as Kirk moves on the south side of a low- to mid-level ridge. The latest models have not changed much, and the NHC track forecast lies near the middle of the guidance envelope. This forecast takes Kirk across the Lesser Antilles later today as a tropical storm.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 13.5N  58.3W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 12H  27/1800Z 14.2N  60.2W   45 KT  50 MPH - Tropical Storm (ESE Sainte-Anne, Martinique)
 24H  28/0600Z 14.9N  62.5W   40 KT  45 MPH - Tropical Storm (WSW Scotts Head, Dominica)
 36H  28/1800Z 15.6N  64.7W   35 KT  40 MPH - Tropical Storm (WSW Grande-Anse, Guadeloupe)
 48H  29/0600Z 16.0N  67.0W   30 KT  35 MPH - Tropical Storm (WSW Ponce, Puerto Rico)
 72H  30/0600Z 16.3N  71.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  01/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Wed Sep 26 2018

Tropical Storm Kirk  The storm’s cloud pattern now has a more comma-shaped appearance, with the estimated center near the western edge of the comma head. Some low-cloud lines are becoming exposed over the western portion of the circulation, which is suggestive of some increase in vertical shear. Based on flight-level and uncontaminated SFMR winds from the Air Force Hurricane Hunter mission a few hours ago, the intensity is kept at 50 kt for this advisory. The dynamical guidance is in good agreement that the shear will increase significantly in 18 to 24 hours, and a weakening trend is likely to commence around that time. The system is predicted to dissipate due to the strong shear over the Caribbean Sea in about 5 days, and several of the reliable global models show this occurring even sooner. The official intensity forecast is similar to the latest multi-model consensus, IVCN, which has been a good performer in the Atlantic basin so far this year.

Kirk is moving west-northwestward, or 285/16 kt. A pronounced mid-level ridge over the southwestern North Atlantic and Florida should continue to steer Kirk on a west-northwestward to westward heading through the forecast period. Based on the latest track model guidance, the official forecast is somewhat faster than the previous one and now takes Kirk over the Lesser Antilles in about 24 hours. On this basis, the arrival of tropical-storm-force winds in the warning area is a few hours earlier than implied by the previous advisory. For specific timing information, please consult the latest arrival time of tropical-storm-force winds graphic on the National Hurricane Center website.

FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 12.7N  55.7W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 12H  27/0600Z 13.5N  57.9W   50 KT  60 MPH - Tropical Storm (ESE Ilet Chevalier, Martinique)
 24H  27/1800Z 14.4N  60.2W   45 KT  50 MPH - Tropical Storm (ESE Sainte-Anne, Martinique)
 36H  28/0600Z 15.1N  62.5W   40 KT  45 MPH - Tropical Storm (WSW Scotts Head, Dominica)
 48H  28/1800Z 15.7N  65.0W   35 KT  40 MPH - Tropical Storm (WSW Trois-Rivières, Guadeloupe)
 72H  29/1800Z 16.3N  70.0W   25 KT  30 MPH - Tropical Storm (WSW Santo Domingo, Dominican Republic)
 96H  30/1800Z 15.7N  74.0W   20 KT  25 MPH - Tropical Storm (WSW Les Cayes, Haiti)
120H  01/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 PM AST Wed Sep 26 2018

KIRK STRENGTHENS SOME MORE BUT LITTLE ADDITIONAL CHANGE IN STRENGTH EXPECTED THROUGH THURSDAY… SUMMARY OF 200 PM AST…1800 UTC…

Tropical Storm Kirk

INFORMATION

LOCATION…12.5N 55.0W

ABOUT 305 MI…495 KM E OF BARBADOS

ABOUT 430 MI…695 KM ESE OF MARTINIQUE

MAXIMUM SUSTAINED WINDS…60 MPH…95 KM/H

PRESENT MOVEMENT…W OR 280 DEGREES AT 18 MPH…30 KM/H

MINIMUM CENTRAL PRESSURE…998 MB…29.47 INCHES

NWS National Hurricane Center Miami FL 1100 AM AST Wed Sep 26 2018

Tropical Storm Kirk is maintaining a CDO of strong convection over its center, but banding features are limited. Observations from an Air Force Reserve Unit Hurricane Hunter aircraft along with scatterometer data indicate that the storm has strengthened a little and the maximum winds are now near 45 kt. The SHIPS model output shows a large increase in westerly shear over Kirk within 18-24 hours. Therefore not much additional strengthening is likely, and a weakening trend should commence in a day or so. The official intensity forecast is similar to the latest model consensus. Strong westerly shear is likely to continue to adversely affect Kirk while it moves over the Caribbean, and the system should weaken into a depression within 72 hours or sooner, and become a remnant low later in the forecast period.

The motion is a little north of due west, or 280/16 kt. The steering pattern for Kirk is rather straightforward. A subtropical high pressure area over the southwestern North Atlantic is expected to persist and retrograde slightly westward over the forecast period. The flow on the southern side of the high should steer Kirk on a westward to west-northwestward track for the next several days. The official track forecast is close to the corrected dynamical model consensus, HCCA, and is very similar to the previous NHC track.

FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 12.1N  54.3W   45 KT  50 MPH - Tropical Storm (ESE  Bridgetown, Barbados)
 12H  27/0000Z 12.7N  56.1W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 24H  27/1200Z 13.7N  58.7W   45 KT  50 MPH - Tropical Storm (ESE Vieux Fort, Saint Lucia)
 36H  28/0000Z 14.5N  61.0W   40 KT  45 MPH - Tropical Storm (WSW Roseau, Dominica)
 48H  28/1200Z 15.2N  63.2W   35 KT  40 MPH - Tropical Storm (WSW Roseau, Dominica)
 72H  29/1200Z 16.0N  68.0W   30 KT  35 MPH - Tropical Storm (S Isla De Mona, Puertp Rico)
 96H  30/1200Z 16.0N  72.0W   25 KT  30 MPH - Tropical Storm (ESE Cabo Rojo, Dominican Republic)
120H  01/1200Z 16.0N  76.0W   20 KT  25 MPH - Tropical Storm (ESE Morant Bay. Jamaica)

NWS National Hurricane Center Miami FL 200 AM EDT Wed Sep 26 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: Tropical Storm Kirk

Thunderstorm activity has increased and become better organized in association with the remnants of Kirk located about 650 miles east of the Windward Islands. Recent satellite-derived wind data also indicate that the circulation has become better defined and that the winds have increased. If this development trend continues, then advisories will be re-initiated on this system later this morning. Interests in the Windward and Leeward Islands should monitor the progress of this disturbance. An Air Force Reserve reconnaissance aircraft is schedule to investigate this disturbance later today. For more information on this system, see High Seas Forecasts issued by the National Weather Service.

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

NWS National Hurricane Center Miami FL 800 PM EDT Tue Sep 25 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The remnants of Tropical Storm Kirk are located about 750 miles east of the Windward Islands and are moving quickly westward at 20 to 25 mph. The associated shower and thunderstorm activity has become a little better organized during the last several hours, however, the system still appears to lack a closed circulation. This disturbance is likely to redevelop into a tropical cyclone during the next day or two before it moves into an area of highly unfavorable upper-level winds as it approaches the Caribbean Sea.

Interests in the Windward and Leeward Islands should monitor the progress of this disturbance as gusty winds and locally heavy rains are likely over the next couple of days even if the system does not redevelop into a tropical cyclone. For more information on this system, see High Seas Forecasts issued by the National Weather Service. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Tue Sep 25 2018

The remnants of Kirk are located about 950 miles east of the Windward Islands and are moving quickly westward at around 25 mph. This system continues to produce a large area of showers and thunderstorms, along with winds to near gale force in gusts on its north side. However, satellite data indicate that the system still lacks a closed circulation. This disturbance could redevelop into a tropical cyclone during the next day or two before it moves into an area of highly unfavorable upper-level winds while it approaches the Caribbean Sea. Interests in the Windward and Leeward Islands should monitor the progress of this disturbance as gusty winds and locally heavy rains are likely over the next couple of days even if the system does not redevelop into a tropical cyclone. For more information on this system, see High Seas Forecasts issued by the National Weather Service.

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

NWS National Hurricane Center Miami FL 200 AM EDT Tue Sep 25 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on recently downgraded Subtropical Depression Leslie, located about 1200 miles west of the Azores.

The remnants of Kirk are located about 1100 miles east of the Windward Islands and are moving quickly westward at around 25 mph. This system continues to produce a large area of showers and thunderstorms, along with winds to gale force on its north side. However, satellite data indicate that the system still lacks a closed circulation. This disturbance could redevelop into a tropical cyclone during the next couple of days before it moves into an area of highly unfavorable upper-level winds while it approaches the Caribbean Sea. Interests in the Windward and Leeward Islands should monitor the progress of this disturbance as gusty winds and locally heavy rains are likely even if the system does not redevelop into a tropical cyclone. For more information on this system, see High Seas Forecasts issued by the National Weather Service. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Mon Sep 24 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on Subtropical Storm Leslie, located about 1200 miles west of the Azores.

A tropical wave, the remnants of Kirk, is located about 1300 miles east of the Windward Islands. This system could redevelop into a tropical cyclone during the next few days before it encounters highly unfavorable upper-level winds while it approaches the Caribbean Sea. For more information on this system, see High Seas Forecasts issued by the National Weather Service.

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

NWS National Hurricane Center Miami FL 200 PM EDT Mon Sep 24 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: The National Hurricane Center has stopped issuing advisories on Tropical Depression Kirk, located about 1100 miles west-southwest of the Cabo Verde Islands, and continues to issue advisories on Subtropical Storm Leslie, located about 1200 miles west of the Azores.

A tropical wave, the remnants of Kirk, is located about 1400 miles east of the Windward Islands. This system is producing showers and thunderstorms along with winds to gale force over the northern portion of the wave. Redevelopment of this system is possible over the next few days until it encounters highly unfavorable upper-level winds while it approaches the Caribbean Sea.

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

NWS National Hurricane Center Miami FL 1100 AM AST Mon Sep 24 2018

Tropical Storm Kirk – Analysis of the directional ambiguities from a recent ASCAT scatterometer overpass indicated that the system lacks the closed circulation that is a prerequisite for tropical cyclone status.

Therefore, advisories are being discontinued at this time. The ASCAT data showed that the system is now a sharp trough accompanied by an area of gale-force winds that will be handled in High Seas Forecasts issued by the National Weather Service.

The remnants of Kirk will be monitored during the next few days in case regeneration into a tropical cyclone should occur.

NWS National Hurricane Center Miami FL 500 PM AST Sun Sep 23 2018

Tropical Storm Kirk’s deep convection has diminished near the estimated center of Kirk, and the main thunderstorm activity is occurring over the northwestern and western peripheries of the circulation. This has the appearance of an arc cloud, suggesting that some drier mid-level air has been entrained into the tropical cyclone. Since the system should be moving over warmer waters and through low vertical shear for the next day or so, some strengthening is anticipated into early this weak. Later in the forecast period, Kirk should be encountering increasing shear associated with strong upper-level westerlies over the Caribbean, and this will likely cause weakening. The official forecast is close to the latest Florida State University Superensemble prediction and is the same as the previous NHC forecast.

Based on the latest center fixes, the motion continues swiftly toward the west, or about 280/20 kt. A mid-level subtropical ridge to the north of Kirk should steer the tropical cyclone westward at a fairly fast clip for the next couple of days. By days 3-4, the ridge weakens a bit and Kirk should slow its forward motion somewhat. The official track forecast has not changed much from the previous advisory and is close to the latest corrected consensus model, HCCA, prediction.

FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z  9.5N  32.3W   35 KT  40 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 12H  24/0600Z  9.9N  35.3W   40 KT  45 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 24H  24/1800Z 10.2N  39.5W   45 KT  50 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 36H  25/0600Z 10.4N  43.4W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 48H  25/1800Z 10.6N  47.1W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 72H  26/1800Z 11.6N  53.4W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 96H  27/1800Z 12.9N  58.1W   40 KT  45 MPH - Tropical Storm (ESE Bridgetown, Barbados)
120H  28/1800Z 14.0N  63.0W   35 KT  40 MPH - Tropical Storm (WNW Castries, St. Lucia)

NWS National Hurricane Center Miami FL 1100 AM AST Sun Sep 23 2018

Tropical Storm Kirk’s cloud pattern has a figure 6 configuration, with most of the deep convective bands over the western semicircle of the circulation. Microwave imagery indicates that the center is near the eastern side of the main area of deep convection, as before. Dvorak classifications from both TAFB and SAB support keeping the intensity at 35 kt. The storm will be moving over warmer waters with fairly low shear for the next day or two, so some strengthening is anticipated in the short term. Later in the forecast period, increasing westerly shear should cause weakening. The official intensity forecast is similar to the model consensus through 48 hours, and follows the trends shown by the ECMWF and GFS global guidance thereafter. The latter models suggest that Kirk could open up into a trough when it nears the Caribbean.

Center fixes indicate that Kirk has been accelerating westward and the initial motion estimate is now 280/18 kt. A well-defined mid-level ridge to the north of the cyclone should cause an even faster westward motion over the next few days. Near the end of the forecast period, a weakness in the ridge is likely to lead to a slowing of the forward speed. The official forecast is a blend of the latest simple and corrected model consensus forecast tracks and is also similar to the previous NHC track.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z  9.3N  30.2W   35 KT  40 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 12H  24/0000Z  9.8N  33.2W   40 KT  45 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 24H  24/1200Z 10.2N  37.3W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 36H  25/0000Z 10.5N  41.5W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 48H  25/1200Z 10.7N  45.6W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 72H  26/1200Z 11.2N  52.4W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 96H  27/1200Z 12.3N  57.5W   40 KT  45 MPH - Tropical Storm (ESE Bridgetown, Barbados)
120H  28/1200Z 13.5N  62.0W   35 KT  40 MPH - Tropical Storm (ESE Bridgetown, Barbados)

NWS National Hurricane Center Miami FL 500 PM AST Sat Sep 22 2018

The convection associated with Tropical Storm Kirk  is currently disorganized, with the majority of it in a cluster to the west of the center. Most of the subjective and objective satellite intensity estimates are in the 30-35 kt range, so the initial intensity remains 35 kt for this advisory.

The forecast track takes Kirk over SSTs around 27C for the next 36 h or so with generally low shear, which appears favorable for gradual strengthening. However, there is a possibility that entrainment of dry air from an area of African dust present to the north of Kirk may allow less intensification than currently forecast. From 36-72 h, there is some divergence in the intensity guidance between the SHIPS and LGEM models, which forecast strengthening into a hurricane, and the dynamical models, which forecast little additional strengthening. The intensity forecast leans toward the dynamical models during that period. After 72 h, Kirk should encounter increasing westerly shear and gradually weaken. The intensity forecast, which is unchanged from the previous forecast, lies a little above the intensity consensus IVCN.

The initial motion is now 290/13. The subtropical ridge to the north of the storm should steer Kirk quickly westward for the next 72 h or so, with forward speeds reaching 20-25 kt. Later in the forecast period, Kirk should turn west-northwestward with a decrease in forward speed as it nears a developing weakness in the ridge near and to the east of the Lesser Antilles. The new forecast track, which is closest to the HCCA consensus model, is shifted a little to the north of the previous track. However, it continues to lie on the south side of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z  8.6N  24.8W   35 KT  40 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 12H  23/0600Z  9.1N  27.1W   40 KT  45 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 24H  23/1800Z  9.5N  31.2W   45 KT  50 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 36H  24/0600Z  9.7N  35.7W   50 KT  60 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 48H  24/1800Z  9.8N  40.2W   50 KT  60 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 72H  25/1800Z 10.5N  48.0W   50 KT  60 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 96H  26/1800Z 11.5N  54.0W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)
120H  27/1800Z 13.0N  59.0W   40 KT  45 MPH - Tropical Storm (ESE Bridgetown, Barbados)

NWS National Hurricane Center Miami FL 1100 AM AST Sat Sep 22 2018

The area of low pressure located well south of the Cabo Verde Islands now has a well-defined center and enough organized deep convection to be considered a tropical cyclone. The initial intensity is set to 35 kt based on data from recent ASCAT passes that showed an area of 30-35 kt winds northwest of the center.

Tropical Storm Kirk will be moving over SSTs around 27C for the next 36 hours or so with generally low shear, which should allow for some gradual strengthening. After that time, the SSTs increase quickly along the forecast track, but the SHIPS model and global model fields show the vertical shear increasing, in part due to the very fast low-level easterly flow. In addition, the GFS and ECMWF global models don’t show much development of the cyclone during the forecast period. As a result of these factors, little change in strength is forecast after 48 hours. The NHC forecast is close to the HCCA consensus aid through 48 hours and is near IVCN afterward.

The initial motion estimate is 280/12, but has the usual uncertainty for a system in the early stages of development. The cyclone is expected to be steered very quickly westward at low latitudes with forward speeds reaching 20-25 kt over the next 72 hours to the south of a mid-level ridge. Late in the period, some gain in latitude and a slight decrease in forward speed are shown as a weakness in the ridge develops to the east of the Lesser Antilles. The initial NHC track forecast is close to HCCA and a little south of the TVCA consensus, giving a little more weight to the GFS and ECMWF, which lie on the south side of the track guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z  8.3N  23.6W   35 KT  40 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 12H  23/0000Z  8.8N  25.7W   40 KT  45 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 24H  23/1200Z  9.3N  29.6W   45 KT  50 MPH - Tropical Storm (WSW São Filipe, Cape Verde)
 36H  24/0000Z  9.4N  34.0W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 48H  24/1200Z  9.6N  38.6W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 72H  25/1200Z 10.3N  46.8W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
 96H  26/1200Z 11.0N  53.0W   50 KT  60 MPH - Tropical Storm (ESE Bridgetown, Barbados)
120H  27/1200Z 12.5N  58.5W   45 KT  50 MPH - Tropical Storm (ESE Bridgetown, Barbados)

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Recent Tropical Storms

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