recursal/Fanatic-Fandom huggingface dataset:
Atlantic/2015/02L/Archive/21

## Public advisory

TROPICAL DEPRESSION BILL ADVISORY NUMBER 21

WIKI-HURRICANES FORECAST CENTER

1000AM CDT SAT JUN 20 2015

... RESILIENT BILL CONTINUES TO PRODUCE ORGANIZED CONVECTION ...

SUMMARY OF 1000AM CDT...1500 UTC...INFORMATION

LOCATION... 38.2N, 85.0W

ABOUT 40MI... 65KM E OF LOUISVILLE, KENTUCKY

MAXIMUM SUSTAINED WINDS...15 KT...20 MPH...30 KM/H

MINIMUM BAROMETRIC PRESSURE... 1004 MB...29.65 INCHES

PRESENT MOVEMENT...ENE AT 17 KT...20MPH...30 KM/H

DISCUSSION AND 48-HOUR OUTLOOK

At 1000 am CDT, the center of Tropical Depression Bill was located at 38.2N, 85.0W, or about 40 miles (65 kilometers) east of Louisville, Kentucky. Maximum sustained winds were 15 knots (20 mph, 30 km/h), with higher gusts. The minimum barometric pressure was 1004 millibars (hPa; 29.65 inHg), and the system was moving east-northeast at 17 knots (20 mph, 30 km/h). Bill is still expected to become a remnant low and merge with another extratropical system within the next 48 hours.

NEXT ADVISORY

Next complete advisory at 400 pm CDT.

$$

Forecaster TheAustinMan

## Discussion

TROPICAL DEPRESSION BILL DISCUSSION NUMBER 21

WIKI-HURRICANES FORECAST CENTER

1000AM CDT SAT JUN 20 2015

Bill continues to produced organized convection over the Ohio River Valley. Radar imagery depicted continued spiral banding and central shower activity with the storm near Frankfort, Kentucky, near the Appalachian Mountains. This kind of inland tropical cyclone persistence has largely been unprecedented, but regardless, Bill is still expected to slowly weaken and become disrupted over Appalachia before merging with an extratropical cyclone in 24 hours.

INIT 20/1500Z 38.2N 85.0W 15KT 20MPH

12HR 21/0000Z 38.9N 82.0W 15KT 20MPH ... TROPICAL DEPRESSION

24HR 21/1200Z ... MERGED WITH EXTRATROPICAL CYCLONE

$$

Forecaster TheAustinMan
Atlantic/2018/02L/Archive/13

Subtropical Storm Beryl Discussion Number 13

Wiki-Hurricanes Forecast Center

11:00 AM AST Sun Jul 15 2018

Beryl is comprised of a small but well-defined low-level circulation, with intermittent and small bursts of shower activity to the south and east of its center. Satellite intensity estimates are ST2.5/35kt from TAFB and T2.6/37kt from UW-CIMSS ADT. In addition, a recent ASCAT pass showed two 35kt barbs within the convective activity. Therefore, the initial intensity is raised to 35kt.

The small bursts of convection are barely maintaining Beryl as a (sub)tropical cyclone. It is only a matter of time before the strong 25-30kt of wind shear, ocean temperatures below 26C, and mid-level relative humidity values below 50 percent put an end to this convection, rendering Beryl a remnant area of low pressure. This is expected to occur within 12 hours. The system is currently moving northeast around a mid-level ridge to its east, and this track should send the remnants into Newfoundland in about 48 hours. No significant impacts are expected.

FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 35 KT 40 MPH...SUBTROPICAL STORM

12H 16/0000Z 30 KT 35 MPH...POST-TROP/REMNT LOW

24H 16/1200Z 30 KT 35 MPH...POST-TROP/REMNT LOW

36H 17/0000Z 25 KT 30 MPH...POST-TROP/REMNT LOW

48H 17/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW

72H 18/1200Z...DISSIPATED
Atlantic/2019/05L/Archive/24

Dorian is in the midst of rapid intensification. Continuous lightning is ongoing within the eye of the intense hurricane as deep convection rotates around the center. The eye itself has become increasingly warm as a slight layer of upper-level wind shear that was plaguing the system yesterday subsides. In the absence of reconnaissance data, a blend of satellite intensity estimates supports upgrading the hurricane to 105kt. That being said, I fully believe this estimate to be low given the current presentation on satellite. A new reconnaissance plane will be in Dorian within the next few hours to assess its true, likely monstrous, strength.
The environment around Dorian could not be better suitable to significant development. The hurricane is exhibiting two well-defined outflow channels, one toward the west courtesy of a weakening upper-level trough near the Florida Straits, and one toward the southeast courtesy of an upper-level ridge north of Puerto Rico. Ocean temperatures remain in excess of 28C while 700-500mb relative humidity values continue to steadily rise. Thus, the main factor controlling the intensity of Dorian prior to land interaction will be inner core processes that cannot be predicting far in advance. A recent microwave pass was at least suggestive than an eyewall replacement is likely to occur over the next 24 hours. The updated intensity forecast has again been increased, and chances are increasing that Dorian comes close to Category 5 strength over the coming days. Weakening is expected as the hurricane interacts with Florida, though given an eastward shift in guidance, the weakening trend is expected to be slower.
Recon fixes and satellite imagery indicates Dorian may be beginning its turn toward the west-northwest. A further turn toward the west is expected by late tomorrow, with that motion expected to continue through 72 hours. Beyond that time, an upper-level trough over the northern United States should erode high pressure off the Southeast coastline, forcing the hurricane to curve toward the north. The exact timing of Dorian will determine whether this curve occurs before or after potential landfall, with an increasing number of models suggesting the curve may occur along the coastline of Florida or perhaps even offshore. The best course of action for now is to continue forecasting landfall along the eastern coastline of Florida. However, Dorian is not expected to progress substantially far inland even if that remains true.
FORECAST MAX WINDS
INIT 30/2100Z 105 KT 120 MPH
12H 30/0600Z 115 KT 130 MPH
24H 31/1800Z 120 KT 140 MPH
36H 31/0600Z 120 KT 140 MPH
48H 01/1800Z 125 KT 145 MPH
72H 02/1800Z 130 KT 150 MPH
96H 03/1800Z 120 KT 140 MPH...NEAR THE COAST
Atlantic/2018/03L/Archive/13

Hurricane Chris Discussion Number 13

Wiki-Hurricanes Forecast Center

5:00 AM EDT Wed Jul 11 2018

Chris has changed little in appearance the past few hours as it passes over a pocket of slightly cooler ocean temperatures. The central dense overcast has shrunk, but convection has become more symmetric, especially to the east. That being said, the eye has cooled slightly and become less circular. Satellite intensity estimates are generally around 90kt, and the initial intensity is held at the strength.

The system should move away from the aforementioned cold pocket later this morning, and environmental conditions remain seemingly favorable for strengthening, especially as Chris interacts with the upper-level trough to its north. Late tonight into tomorrow morning, the hurricane should cross the sharp SST gradient of the Gulf Stream and become more wholly involved with the trough, causing extratropical transition around 36 hours from now. The system is moving northeast, and that motion should continue for the next several days, bringing Chris close to Newfoundland. A turn more toward the east is expected before it dissipates in 4 days.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 90 KT 105 MPH

12H 11/1800Z 95 KT 110 MPH

24H 12/0600Z 100 KT 115 MPH

36H 12/1800Z 85 KT 100 MPH...POST-TROP/EXTRATROP

48H 13/0600Z 60 KT 70 MPH...POST-TROP/EXTRATROP

72H 14/0600Z 45 KT 50 MPH...POST-TROP/EXTRATROP

96H 15/0600Z...DISSIPATED

120H 16/0600Z...DISSIPATED
Atlantic/2019/06L/Archive/10

Erin was on the verge of becoming a remnant low this evening, but in recent hours deep convection has managed to save the system. Still, the circulation is in the process of becoming increasingly elongated, and Erin is likely to become a strengthening extratropical low tomorrow as it merges with a frontal system. The storm is now moving north-northeast at an increasingly rapid pace, and on that trajectory Erin should strike Nova Soctia tomorrow night.
FORECAST MAX WINDS
INIT 28/0300Z 30 KT 35 MPH
12H 29/1200Z 30 KT 35 MPH...POST-TROP/EXTRATROP
24H 29/0000Z 35 KT 40 MPH...POST-TROP/EXTRATROP
36H 30/1200Z 35 KT 40 MPH...POST-TROP/EXTRATROP
Atlantic/2019/05L/Archive/4

Tropical Storm Dorian has become better organized today, with persistent deep convection over the low-level circulation and expanding upper-level outflow. All recent ASCAT passes missed and, until recently, so too did microwave passes. That being said, a just-released 1922z SSMISS pass showed a tightly-curved band that may be the start of a formative eyewall. Satellite intensity estimates range as low as T2.5/35kt from SAB to as high as 64kt from AMSU. Given the increase in organization since the last advisory, the initial intensity has been increased to 45kt, in line with T3.0/45kt from TAFB.
Dorian continues its westward track today, steered by an expansive mid-level ridge north and east of the Caribbean islands. Over the coming days, this ridge will weaken and yield itself to a massive subtropical ridge east of Bermuda, as well as a mid-level trough to the west of the aforementioned island. This should cause Dorian to move northwest once in the Caribbean Sea, a change that brings the system across Hispaniola.
The intensity forecast continues to be, by far, the most challenging part of Dorian's forecast. Wind shear has decreased to around 5kt and should remain favorable for the next 60 hours or so. Ocean temperatures, now 28C, should rise to 29-30C over the coming days. Thus, the only limiting factor in the short term is expected to be dry 700-500mb relative humidity values around 40-50 percent. Dorian's small size should make the storm especially susceptible to dry air intrusions. On the flip side, if the cyclone is able to mix out this dry air effectively, its small size may also allow a rapid increase in strength. The SHIPS rapid intensification index posted a 44 percent chance of 65kt rapid development over the next 3 days, a number over eight times the climatological mean. Models offer no clarity this afternoon, with dynamical guidance SHIPS/LGEM indicating a Category 1 hurricane and global models showing dissipation in the eastern Caribbean. One change has been in the HWRF model, which has gone from depicting a major hurricane to depicting a solution more in line with the globals. As I mentioned in the first advisory, in previous cases similar to this one, global models tend to perform better. It remains probable, though, that globals are underselling Dorian's intensity prior to the storm encountering increased shear. For the purpose of this advisory, I have decreased Dorian's peak intensity (while still depicting a hurricane) and indicate some weakening before Hispaniola. This will be followed by rapid weakening over the island. The possibility that Dorian dissipates while inland is appreciable, while it would not be shocking to see a steady-state hurricane if Dorian passes east of Hispaniola either.
FORECAST MAX WINDS
INIT 25/2100Z 45 KT 50 MPH
12H 26/0600Z 50 KT 60 MPH
24H 26/1800Z 55 KT 65 MPH
36H 27/0600Z 60 KT 70 MPH...MOVING THROUGH LEEWARD ISLANDS
48H 27/1800Z 65 KT 75 MPH
72H 28/1800Z 70 KT 80 MPH
96H 29/1800Z 60 KT 70 MPH...LANDFALL IN HISPANIOLA
Atlantic/2018/03L/Archive/16

Hurricane Chris Discussion Number 16

Wiki-Hurricanes Forecast Center

11:00 PM EDT Wed Jul 11 2018

Chris is beginning to make its steps toward becoming an extratropical cyclone. The eye has collapsed, and dry air is wrapping into the southern semicircle of the hurricane. Satellite intensity estimates at 0z were T4.0/65kt from both TAFB and SAB, and the final T-number from UW CIMSS ADT has decreased to T4.8/84.8kt. A simple blend of these values yields 70kt; however, given that Chris is still over marginally warm waters and its degradation in appearance is fairly new, the initial intensity has been set at 75kt instead.

The amount of time left for Chris to remain as a tropical entity is rapidly closing. The storm is beginning to cross the sharp gradient of the Gulf Stream and should enter ocean temperatures cooler than 12C within 18 hours. Increased interaction between the storm and the upper-level trough directing it northeast should increase southwesterly wind shear to over 25kt by that time as well. Finally, mid-level relative humidity values are forecast to fall below 50 percent; in the absence of an inner core and in the presence of strong wind shear, this should prove harmful to Chris. Extratropical transition is now expected around 18 hours from now, although this process could occur a few hours earlier given how cold the waters of the North Atlantic are.

On its current trajectory, Chris is expected to just southeast of Newfoundland in about 24 hours, delivering tropical storm-force winds and heavy rainfall, in addition to rough surf and high rip currents offshore. Chris should continue into the far North Atlantic thereafter, bending more eastward on the southern periphery of a broad mid-latitude low to the east of Greenland.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 75 KT 85 MPH

12H 12/1200Z 65 KT 75 MPH

24H 13/0000Z 55 KT 65 MPH...POST-TROP/EXTRATROP

36H 13/1200Z 45 KT 50 MPH...POST-TROP/EXTRATROP

48H 14/0000Z 35 KT 40 MPH...POST-TROP/EXTRATROP

72H 15/0000Z...DISSIPATED
Atlantic/2018/02L/Archive/9

Tropical Storm Beryl Discussion Number 9

Wiki-Hurricanes Forecast Center

5:00 AM AST Sun Jul 8 2018

Since our last advisory last night, Beryl has fallen off a cliff. Moderate easterly wind shear dissolved its inner core and allowed the infiltration of dry air that eroded all associated convective activity, leaving a bare center of circulation for most of the day. Over the past few hours, aided by the diurnal maximum and warmer ocean temperatures, the storm has been able to fire a large but disorganized mass of showers and thunderstorms. An 0110z ASCAT pass indicated maximum winds near 35kt to the north of the center, but given the low bias of the instrument, the small size of Beryl, and the temporary uptick in organization, the initial intensity has been set at 40kt.

Beryl is moving west-northwest under the influence of a large subtropical ridge to its north. This trajectory should take it into the eastern Caribbean Sea late tonight or early tomorrow morning. Whatever remains of Beryl thereafter should be directed into Hispaniola, and eventually into the southwestern Atlantic. On its current path, Beryl should deliver localized heavy rainfall and tropical storm-force winds to portions of the Leeward Islands

We knew the environment would be hostile to Beryl as it neared the Caribbean, and that has fully materialized. Wind shear has increased to around 15kt and is expected to rise to over 30kt within 36 hours. This shear will help to inject dry air into the circulation, characterized by mid-level relative humidity values around 50 percent. Water temperatures continue to increase along the path of the system, but its small size and the otherwise unfavorable upper-level environment should prevent any intensification. Beryl is likely to dengerate to an open tropical wave within 24 to 36 hours. If the disturbance is able to cross Hispaniola intact, environmental conditions may become more conducive for regeneration in the southwestern Atlantic in a few days, as indicated by the FV3, UKMET, and ECMWF. It is still too early to say with any certainty.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 40 KT 45 MPH

12H 08/1800Z 35 KT 40 MPH

24H 09/0600Z 30 KT 35 MPH

36H 09/1800Z...DISSIPATED
Atlantic/2019/08L/Archive/18

Gabrielle continues to organize this morning. Infrared satellite shows increased symmetry of convection around its formative eye feature, with spiral banding persisting in the southwest quadrant. Upper-level outflow appears restricted on the east as a result of easterly wind shear. Dvorak intensity estimates remain the same as six hours ago, but the increase in symmetry supports an upgrade to 50 kt.
Gabrielle continues to experience the effects of higher than forecast shear. It is possible that wind shear could decrease over the next day or so as the storm establishes itself, increasing the environmental favorability, allowing the storm to intensify a bit more than currently forecast. With warm ocean temperatures near 28-29C, wind shear will continue to be the main factor limiting Gabrielle's intensity. Sea surface temperatures will decrease rapidly in about 30h as the storm enters a baroclinic environment, resulting in transition to an extratropical cyclone. Dissipation is expected in about 4 days.
Gabrielle is beginning its northerly turn as the storm is currently tracking northwest around a mid-level ridge located west of the Azores. With Ex-Dorian approaching, heights north of Gabrielle will fall, resulting in the continuation of the northerly turn and further toward the northeast by the end of day 2. The storm should accelerate northeast as it becomes embedded in the mid-latitude westerlies.
FORECAST MAX WINDS
INIT 07/0300Z 50 KT 60 MPH
12H 07/1200Z 55 KT 65 MPH
24H 08/0000Z 60 KT 70 MPH
36H 08/1200Z 65 KT 75 MPH
48H 09/0000Z 60 KT 70 MPH
72H 10/0000Z 45 KT 50 MPH...POST-TROP/EXTRATROP
Atlantic/2019/09L/Archive/15

The large Hurricane Humberto has increased slightly in organization over the last few hours. Although the central dense overcast and eyewall regions remain somewhat ragged in infrared satellite imagery, the eye has become marginally more cloud-free and circular during this time. Microwave data shows a large and loose eyewall partially open to the south. At 18z SAB estimated an intensity of T5.5/102kt while automated estimates from UW-CIMSS were higher still at T6.0/112kt. Based on the trends from the previous advisory and the reconnaissance data at that time relative to satellite-derived pressures, the current intensity has been increased slightly to 90kt.
Now in a highly divergent jet-assisted flow regime, Humberto is expected to strengthen further atop warm waters of 27-28C in the Sargasso Sea. The storm's structure is not ideal for intensification, but the system will remain within an unstable environment and is moving slow enough for greater coalescence to take shape over the next day or two. Most of the dynamical guidance shows a blend between tropical and barolinic forcings intensifying the system to a peak at or near major hurricane intensity in 24-36 hours. Afterwards, more unfavorable shear vectors from a downward progressing upper-level low are expected to weaken the storm, with its intensity diminishing over time as extratropical transition occurs. Between days 2-3, Humberto is expected to take on hybrid characteristics. Extratropical transition is expected to complete in 4-5 days, but this transformative mechanism is one of the more complex cases we've seen in the last few years.
Although the track forecast is a little strange overall, we have higher confidence over the forecast motion today. After Humberto is guided by the trough to the east-northeast for the next 36 hours, it is expected to curve north in response to an upper-level low passing to its west and southwest. A slowdown and subsequent turn back to the east-northeast is expected after three days as Humberto is caught again by the high-latitude jet, with motion continuing to the end of the forecast period. Humberto is expected to pass roughly 100 miles northwest of Bermuda in approximately 24 hours. Tropical storm winds and hurricane-force gusts are highly likely for the islands.
FORECAST MAX WINDS
INIT 17/2100Z 90 KT 105 MPH
12H 18/0600Z 95 KT 110 MPH
24H 18/1800Z 100 KT 115 MPH
36H 19/0600Z 100 KT 115 MPH
48H 19/1800Z 85 KT 100 MPH
72H 20/1800Z 70 KT 80 MPH
96H 21/1800Z 65 KT 75 MPH
Atlantic/2019/09L/Archive/17

Humberto has maintained intensity overnight, with satellite appearance remaining stable since the last aircraft reconnaissance flight fixed 100 kt. Intensity will remain unchanged for this updated.
Conditions remain favourable for further strengthening, however with the lack of significant convective changes in the past 6 hours, it seems unclear if there will be any further strengthening of the storm. After 24 hours, shear will increase and water temperatures will decrease resulting in fast weakening.

FORECAST MAX WINDS
INIT 18/0900Z 100 KT 115 MPH
12H 18/1800Z 100 KT 115 MPH
24H 19/0600Z 100 KT 115 MPH
36H 19/1800Z 90 KT 105 MPH
48H 20/0600Z 80 KT 95 MPH
72H 21/0600Z 65 KT 75 MPH
96H 22/0600Z 55 KT 65 MPH...POST-TROP/EXTRATROP
Atlantic/2019/01Q/Archive/1

Tropical Depression One-Q Discussion Number 1

Wiki-Hurricanes Forecast Center

6:00 PM AST Sat Mar 23 2019

High-resolution visible imagery from this afternoon indicates that a well-defined low-level circulation has developed approximately 280 miles northeast of Serra, Brazil within a trough of low-pressure extending from Brasilia out into the South Atlantic of sufficient organization to be considered a tropical depression. The center could be readily identified as a vortex of low-level cumuli which has since moved under an area of quickly developing convection with cloud tops cooler than -80C. Tenative banding features are developing in the storm's eastern semicircle, though without recent microwave data it is difficutl to diagnose the storm's internal structure. We have no recent scatterometer data, with the latest being a 00:30 UTC observation of 15 kt winds. Given the robust convection developing and the well-defined ciruclation evident, the initial intensity has been set at an uncertain 25 kt.

One-Q is currently tracking slowly towards the southeast at 135/5 kt in an area of weak steering currents. Conditions are abnormally favorable for tropical intensification in the South Atlantic. Sea surface temperatures off the coast of Brazil range from 28-29C and the vertical thermodynamic profile is well-suited for convective initiation. The system is also well-positioned under an upper-level anticyclone with low shear conditions prevailing. One-Q is expected to gradually intensify in these favorable conditions over the next three days. The later-term intensity forecast for One-Q is highly contingent on its future path which is currently split into two camps in model guidance, with one scenario keeping the system close to the Brazilian coast and perhaps bringing it inland sometime mid-next week with the other scenario capturing One-Q with a trough and bringing it out to sea. In one case the system's intensity will be tempered by land mass, while an increase in wind shear induced by an amplifying trough would eventually cause the system to shear out by day 5. Given the steering layer weakness carved by a disturbance to the southeast, the out-to-sea solution is being favored at this time. The current intensity forecast shows gradual intensification in the next 3 days followed by weakening thereafter.

FORECAST MAX WINDS

INIT 23/2100Z 25 KT 30 MPH

12H 24/0600Z 25 KT 30 MPH

24H 24/1800Z 30 KT 35 MPH

36H 25/0600Z 35 KT 40 MPH

48H 25/1800Z 40 KT 45 MPH

72H 26/1800Z 40 KT 45 MPH

96H 27/1800Z 35 KT 40 MPH

120H 28/1800Z 30 KT 35 MPH...POST-TROP/REMNT LOW
Atlantic/2019/01L/Archive/2

Subtropical Storm Andrea Discussion Number 2

Wiki-Hurricanes Forecast Center

5:00 AM AST Tue May 21 2019

Andrea's convection, still primarily located to the north of its low level circulation, has decreased significantly in the last six hours as the storm continues to interact with an upper level low. The low level center is now partially obscured by cirrus associated with this upper level low encroaching from the south, indicative of modest wind shear. Otherwise, it appears that the cyclone has maintained intensity at 40 kts, given the previous advisory's intensity reasoning.

Wind shear from the upper level low to the southwest of Andrea continues to significantly affect the system, although a brief period of more favorable conditions will arise around 12-18 hour from now where the influence of this shear will wane. Cooler than normal upper tropospheric temperatures should provide the instability to allow for future convective bursts to sustain the system. Andrea is likely to weaken in its current state, but with the potentially less hostile conditions in store for a brief period tomorrow, the storm may be able to maintain or regain intensity. After this period, a cold front, currently fast approaching, will begin to overtake the storm and the system will degenerate rapidly as it is absorbed.

Andrea continues to move north at this time, but during the day tomorrow the storm is expected to turn toward the east as the mid-level ridge axis tilts, no longer pushing the storm north, leaving it in the hands of the jet stream and the approaching cold front. The center of a weakening Andrea is still expected to pass very near to Bermuda where it will have minimal impacts as it is absorbed by the cold front.

FORECAST MAX WINDS

INIT 21/0900Z 40 KT 45 MPH

12H 21/1800Z 40 KT 45 MPH

24H 22/0600Z 35 KT 40 MPH

36H 22/1800Z 30 KT 35 MPH

48H 23/0600Z...DISSIPATED/ABSORBED BY FRONT
Atlantic/2019/08L/Archive/24

Gabrielle looks slightly more robust this afternoon, and I note that this increase of convection was well forecast by HWRF OLR guidance. Despite the interim shenanigans, Gabrielle looks nearly identical to its appearance roughly 24 hours ago, with a curved band in the western semicircle now connected to the incoming trough. A mid-level eye has emerged from this band's curvature, but is displaced well west of the low-level circulation center. SAB estimated T2.5/35kt while UW-CIMSS ADT was higher at T3.3/51kt. I've kept the intensity at 45 kt this advisory based on the earlier ASCAT data and lack of coherence between the low- and mid-levels.
This current convective spell is likely to be the last hurrah from Gabrielle as it enters cooler waters which will are beginning to no longer be supportive of deep convection. Convection should begin to decouple fully from the low-level circulation tonight as the approaching trough undercuts the system, rapidly initiating extratropical transition which should complete around this time tomorrow. Gabrielle will continue tracking rapidly northeast and later east-northeast within the flow of this trough before losing definition over the British Isles in three days.
FORECAST MAX WINDS
INIT 09/2100Z 45 KT 50 MPH
12H 10/0600Z 40 KT 45 MPH
24H 10/1800Z 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 11/0600Z 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 11/1800Z 30 KT 35 MPH...POST-TROP/EXTRATROP
Atlantic/2019/01Q/Archive/9

Tropical Storm Iba Discussion Number 9

Wiki-Hurricanes Forecast Center

06:00 PM AST Mon Mar 25 2019

Not much change has occurred in association with Iba since the last advisory. The system remains encapsulated in a region of moderate to strong northwesterly wind shear, keeping the center of circulation exposed. A burst of convection that initiated in the early afternoon near Iba's center has brought the vortex closer to convection than this morning, briefly covering it. However, Iba's convective structure is quite deformed and the circulation has once again become exposed, and overall convecive intensity has been quickly decreasing this evening. SAB estimates remain at T3.0/45kt, but by previous rationale, recently received ScatSat data from 1030z indicating a swath of 35 kt winds without anything higher, and thus the intensity for Iba remains a possibly generous 40 kt.

No major changes to the track philosophy are introduced in this advisory. However, as the system weakens towards the end of the forecast window, the original vortex might enter a complex interaction with a developing trough axis which makes forecasting the initial disturbance's track rather ambiguous. Nonetheless, the same southward drift followed by southeastward trajectory is anticipated, with a possible slow down and equatorial drift caused by the shallowing cyclone moving with a low level ridging. Although slight intensification was previously forecast, the window of intensification is quickly closing and significant strengthening is becoming unlikely as conditions become increasingly hostile. At this juncture it appears that further intensifcation is unlikely. A slow weakening is projected through much of the forecast, with the possibility of some baroclinic enhancement in the late-term; this uptick in strength is likely more relevant from a system absorbing Iba rather than entirely resulting from Iba's original circulation.

FORECAST MAX WINDS

INIT 25/2100Z 40 KT 45 MPH

12H 26/0600Z 35 KT 40 MPH

24H 26/1800Z 35 KT 40 MPH

36H 27/0600Z 30 KT 45 MPH

48H 27/1800Z 30 KT 35 MPH

72H 28/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW

96H 29/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW

120H 30/1800Z 30 KT 35 MPH...POST-TROP/REMNT LOW
Atlantic/2019/09L/Archive/16

Data from an Air Force reconnaissance aircraft indicates that Humberto has made the climb to major hurricane intensity. The plane measured peak flight-level winds of 112kt, with maximum SFMR winds around 98kt. Both of these numbers support an initial strength of 100kt. In addition, a dropsonde in the southwestern eyewall measured a mean wind of 133kt in the lowest 150m. The most recent eye dropsonde supports a central pressure of 949mb, down another 9mb from the last advisory. Humberto remains well organized on satellite, with deep convection around a large and generally clear eye.
Upper-level winds are expected to remain conducive for another 12 to 24 hours, and ocean temperatures will remain sufficient during that time as well. Thus, the opportunity for further strengthening does exist, especially given the high winds aloft as measured by dropsondes. Beyond that time, a sharp increase in wind shear and dry air coupled with rapidly-cooling ocean waters should result in weakening, with extratropical transition expected about four days from now.
The cyclone is moving off toward the east-northeast. A turn toward the north-northeast or even north is expected between 36 and 72 hours as Humberto interacts with a cut-off mid-level low. By days 4 and 5, however, the cyclone is expected to race toward the east-northeast once again.
FORECAST MAX WINDS
INIT 18/0300Z 100 KT 115 MPH
12H 18/1200Z 105 KT 120 MPH
24H 19/0000Z 110 KT 125 MPH
36H 19/1200Z 100 KT 115 MPH
48H 20/0000Z 85 KT 100 MPH
72H 21/0000Z 65 KT 75 MPH
96H 22/0000Z 55 KT 65 MPH...POST-TROP/EXTRATROP
Atlantic/2019/05L/Archive/14

Dorian is undergoing some further changes this morning as convection begins to fire once again nearer the low-level center. The most recent aircraft reconnaissance pass through the northeast quadrant at around 04z found 55 kt 10-second SFMR with a maximum of about 50 kt flight level winds and a deepening central pressure of 1003 mb. Given the general improvement of the storm, the initial intensity has been raised to 50 kt.
Dorian continues to enjoy a low wind shear environment which will be conducive for its short-term intensification, but model analyses tend to agree that wind shear will increase to around 10 kt, to persist for the next two and a half days or so. This increase in shear may make the system more vulnerable yet again to dry air intrusions, keeping intensification slow. This will be an issue in the short term before Dorian tracks near Puerto Rico later today. It will interact with the island, likely resulting in some weakening and disruption of its inner core. Beyond this, though, conditions look more favorable, while although shear will still remain near 10 kt, increasing mid-level relative humidity should make dry air less of an issue, allowing Dorian to consolidate an inner core more effectively and intensify.
Recently, Dorian has been tracking northwest, as found by aircraft reconnaissance. This track, along the southwest periphery of a mid-level ridge east of Bermuda should continue for about the next 3 days until the ridge builds westward, forcing the storm onto a more west-northwesterly or westerly track, very close to the coast of Florida by the end of the forecast period.
FORECAST MAX WINDS
INIT 28/0900Z 50 KT 60 MPH
12H 28/1800Z 55 KT 65 MPH...APPROACHING PUERTO RICO
24H 29/0600Z 45 KT 50 MPH
36H 29/1800Z 50 KT 60 MPH
48H 30/0600Z 55 KT 65 MPH
72H 31/0600Z 65 KT 75 MPH
96H 01/0600Z 75 KT 85 MPH
Atlantic/2019/08L/Archive/19

The intensity of convection has increased across the southern semicircle of Gabrielle this morning, but little thunderstorm activity exists to the north of the center. Upper-level outflow is impinging from the east, a sign of continued wind shear from a simply different direction compared to days prior. Satellite intensity estimates are unchanged from earlier, and we have no new ASCAT passes as of the time of this advisory, so the initial intensity remains 50kt.
The lack of convection the storm's north side is suggestive that strong upper-level winds are injecting dry air, with mid-level relative humidity values sitting around 40 percent, into the circulation. Water temperatures are beginning to slowly decline, but they remain sufficient for now, so the culmination of environmental factors may allow for some slight intensification over the next 24 to 36 hours. After that, ocean temperatures will rapidly fall into the teens and wind shear will far exceed 40kt. This should cause Gabrielle to become an extratropical cyclone about 48 to 72 hours from now, with dissipation on day 4.
Gabrielle is moving north-northwest this morning, but a turn toward the north and northeast is expected in the coming days as the approach of Dorian and a mid-latitude trough induce southwesterly flow in the mid-layers of the atmosphere. The system will move in that direction at an increasingly rapid pace.
FORECAST MAX WINDS
INIT 08/1500Z 50 KT 60 MPH
12H 09/0000Z 55 KT 65 MPH
24H 09/1200Z 60 KT 70 MPH
36H 10/0000Z 60 KT 70 MPH
48H 10/1200Z 50 KT 60 MPH
72H 11/1200Z 40 KT 45 MPH...POST-TROP/EXTRATROP
Atlantic/2019/12L/Archive/11

Karen has improved this morning. A blob of deep convection only mildly tilted from the centre has developed. The storm is not much better organized though, with the circulation still being very weak on the western side. An ASCAT pass this morning found a tiny area of 35 kt winds, which is the intensity for this advisory.
Conditions remain marginal at best for Karen. Though on paper the environment seems favourable for strengthening, the low level flow has been trying to tear the circulation to shreds. The storm has fought valiantly against this effect though and it seems the storm will maintain intensity better than expected over the next day. By day 3, a ridge to the north of Karen will begin to shear Karen to death. Degeneration into a remnant low is expected by day2 and complete dissipation is expected by the end of the forecast period.
Karen is currently moving northward between a ridge and an upper level low. Later today the storm is expected to turn east from the ridge's influence, before completing a cyclonic loop towards the west from steering influence of a ridge building in over the system.

FORECAST MAX WINDS
INIT 26/1500Z 35 KT 40 MPH
12H 27/0000Z 30 KT 35 MPH
24H 27/1200Z 30 KT 35 MPH
36H 28/0000Z 25 KT 30 MPH
48H 28/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 29/1200Z 20 KT 25 MPH...POST-TROP/REMNT LOW
Atlantic/2018/05L/Archive/4

Subtropical Storm Ernesto Discussion Number 4

Wiki-Hurricanes Forecast Center

5:00 AM AST Thu Aug 16 2018

Ernesto has changed little in organization. Modest convection continues to fire north and east of the low-level circulation, a sign that the immediate environment continues to moisten, but it is not yet centrally focused. Upper-level outflow is not yet expanding either, a sign that Ernesto is still wholly embedded within the upper-level trough that allowed for its formation. There is still opportunity for Ernesto to strength and acquire tropical characteristics today, but a northeast track ahead of an upper-level trough should send the storm into colder waters, a drier environment, and higher wind shear beginning tomorrow. Degeneration to a remnant low is expected in about 24 hours. More recent models are keeping the post-tropical cyclone a separate entity from the frontal system, and this is reflected in the updated forecast, which calls for dissipation in 4 days now.

INIT 16/0900Z 35 KT 40 MPH...SUBTROPICAL STORM

12H 16/1800Z 40 KT 45 MPH...TROPICAL STORM

24H 17/0600Z 40 KT 45 MPH...POST-TROP/EXTRATROP

36H 17/1800Z 40 KT 45 MPH...POST-TROP/EXTRATROP

48H 18/0600Z 45 KT 50 MPH...POST-TROP/EXTRATROP

72H 19/0600Z 35 KT 40 MPH...POST-TROP/EXTRATROP...INLAND OVER UNITED KINGDOM

96H 20/0600Z...DISSIPATED
Atlantic/2019/10L/Archive/4

Jerry continued to strengthen overnight. Deep convection has persisted well overnight and the mid level center has begun to develop a primitive central dense overcast. There is a prominent band to the north of the centre, giving the storm a distinct shrimp like look, a sign of an intensifying moderate tropical storm. The low level centre was confirmed by a microwave pass at 13Z to be dislocated to the northeast of the mid level centre, near the edge of the convective mass. It remains to be seen whether the low level centre will relocate underneath the convection. Preliminary analysis of visible imagery indicates that this could be happening at the moment, but a microwave pass in a few hours will be needed to confirm it. Dvorak estimates are at T3.0/45 kt across the board, so the initial intensity is set at 45 kt.
Jerry's environment remains conducive for strengthening over the next day or so. Shear is forecasted to lessen a bit more, helping to allow the system to stack vertically. However, as the storm intensifies it is likely to pull in dry air from a pocket to its west. This, along with internal issues, should put a damper on the speed of intensification in the short term. By day 2, mid-level shear is expected to pick up and begin impinging on the system. However, overnight the models have begun forecasting less shear and the intensity models now show a steady state hurricane by day 2. Models are inconsistent on how much shear will be impacting the system from day 3 to day 5 but consensus is currently that it will be moderate during most of this period. By day 5, shear could potentially significantly pick up and cause weakening. The intensity forecast now shows quick strengthening to a hurricane by day 2 with little intensity fluctuations for the rest of the period. This forecast is particularly low confidence, with intensity models continuing to show rapidly changing shear conditions in the day 3-5 range.
The system is moving steadily to the west-northwest currently and this motion is not expected to change for the next 72 hours. After this time, Jerry will approach the western edge of the ridge and move northward into a weakness created by Hurricane Humberto. There is some short term track inconsistencies, with the ECMWF model suite showing an increasing split between northwadly and southwardly tracking systems by day 3. This is due to a mid-level ridge which the ensembles show keeping a stronger system further south. While the system is still expected to clear the Lesser Antilles, it is too soon to rule out direct impacts to these islands.

FORECAST MAX WINDS
INIT 18/1500Z 45 KT 50 MPH
12H 19/0000Z 55 KT 65 MPH
24H 19/1200Z 60 KT 70 MPH
36H 20/0000Z 65 KT 75 MPH
48H 21/1200Z 70 KT 80 MPH
72H 22/1200Z 65 KT 75 MPH
96H 23/1200Z 65 KT 75 MPH
Atlantic/2019/05L/Archive/3

Dorian appears similar to the previous advisory. Infrared satellite imagery shows deep convection firing near and west of the center, with some primitive banding on the western side of the storm as well. Outflow is still limited to the east as a result of some easterly shear, despite model diagnostics indicating that shear is in the process of decreasing. Dvorak intensity estimates remain entirely unchanged since the last advisory as well. In the absence of any indications of any changes in intensity, the initial intensity remains 35 kt.
Shear is moderate in the range of 10 kt currently, although it is expected to continue to decrease to around 5 kt or even lower later today. For a system with a small size like Dorian, lower shear will be necessary if the storm is to intensify significantly. Beyond day 2 there is some disagreement in the modelling as to the shear forecast. The global models, which keep the storm weak and weaken it further as it enters the eastern Caribbean forecast higher values of shear compared to the hurricane models. GFS, for example indicates 20 kt shear by day 4 whereas HWRF and HMON are only beginning to rise above 10 kt. Of course, a hurricane is much more likely in the latter scenario where shear is significantly more favorable. The other issue Dorian has to contend with remains low mid-level humidity, currently near 40% but forecast to slowly rise. Sea surface temperatures are warm, near 28C, and are forecast to rise as the storm tracks into the Caribbean. The forecast has been kept much the same this advisory given no significant indications one way or the other. Weakening is expected to occur around day 5 regardless as the storm interacts with the mountainous terrain of the Greater Antilles.
Dorian is tracking just north of west and will slowly curve toward the west-northwest throughout the forecast period as mid-level ridging gradually retracts eastward opening a weakness into which Dorian can head. The storm is expected to pass over the Lesser Antilles near Dominica or Martinique before moving into the Caribbean and tracking toward Hispaniola.
FORECAST MAX WINDS
INIT 25/0900Z 35 KT 40 MPH
12H 25/1800Z 40 KT 45 MPH
24H 26/0600Z 50 KT 60 MPH
36H 26/1800Z 55 KT 65 MPH
48H 27/0600Z 65 KT 75 MPH...APPROACHING LEEWARD ISLANDS
72H 28/0600Z 70 KT 80 MPH...MOVING THROUGH LEEWARD ISLANDS
96H 29/0600Z 75 KT 85 MPH
Atlantic/2019/13L/Archive/13

Large and powerful Hurricane Lorenzo has continued to intensify since the previous advisory. The eye has warmed further to around 18C while the ring of -70C convection has expanded in all directions. Satellite intensity estimates at 0z were T6.5/125kt from SAB and TAFB. More recently, UW-CIMSS ADT has risen to T6.6/129.6kt. An earlier SATCON estimate was in the same ballpark at 128kt. It is worth pointing out that some of these estimates are restricted by Dvorak constraints. The current presentation of Lorenzo is spectacular, indicative of a storm near or Category 5 intensity. Therefore, I have taken the rare step of going above all estimates to assign an initial strength of 135kt.
Upper-level outflow to the west has stopped expanding, an indication that Lorenzo is in the beginning stages of interaction with the upper-level trough to its northwest. In addition, ocean temperatures are hovering around 27C, which is considered marginal for a tropical cyclone of this intensity. Thus, the expectation is that Lorenzo has attained its peak intensity, and a steady-state cyclone or weaker storm should exist over the next few days. One possible exception is around day 4, when wind shear will fall back to near 5kt while ocean temperatures remain marginal; this presents an uncertain potential for re-intensification. Environmental parameters are expected to become hostile by the end of day five, though.
Lorenzo is moving northwest as it remains positioned on the western side of a mid-level ridge. This northwest motion should continue through 36 hours before the hurricane curves north and northeast around the aforementioned area of high pressure. This trajectory should bring Lorenzo near the Azores by the end of day 5.
FORECAST MAX WINDS
INIT 27/0300Z 135 KT 155 MPH
12H 27/1200Z 130 KT 150 MPH
24H 28/0000Z 120 KT 140 MPH
36H 28/1200Z 115 KT 130 MPH
48H 29/0000Z 110 KT 125 MPH
72H 30/0000Z 110 KT 125 MPH
96H 01/0000Z 100 KT 115 MPH
Atlantic/2019/01Q/Archive/3

Tropical Storm Iba Discussion Number 3

Wiki-Hurricanes Forecast Center

6:00 AM AST Sun Mar 24 2019

The cyclone in the South Atlantic has become markedly better organized over the past few hours. Deep convection has exploded near the low-level circulation, and this thunderstorm activity has been accompanied by quite a bit of lightning. In addition, a large and prominent spiral band has taken shape north and east of the low-level circulation. The satellite intensity estimate from SAB was unchanged from the previous advisory; however, this analysis occurred prior to the dramatic changes in appearance we have seen over the past few frames. That change, combined with the fact that the earlier ScatSat pass revealed numerous 30kt wind barbs already, supports upgrading the system to a tropical storm and assigning it the name Iba.

The intensity forecast is fairly tricky, mainly because model spread is large--and in fact has grown since the last advisory. The 0z GFS is now advertising a minimal hurricane, which would make it only the second recorded hurricane on record in the South Atlantic. The 0z ECMWF, meanwhile, has backed off its earlier predictions of intensification and only registers Iba as a weak tropical storm at best. It is unclear what prompted the change in the ECMWF provided that the environment continues to appear conducive over the short term. That being said, the shift in intensity has given me pause in increasing Iba's forecast peak as was originally planned following the completion of the GFS. The storm is still expected to weaken after 72 hours, becoming a post-tropical cyclone the next day. There has been no change in the thinking regarding the track, with a southward drift followed by a curve toward the southeast at an accelerating clip after day three.

FORECAST MAX WINDS

INIT 24/0900Z 35 KT 40 MPH

12H 24/1800Z 40 KT 45 MPH

24H 25/0600Z 45 KT 50 MPH

36H 25/1800Z 45 KT 50 MPH

48H 26/0600Z 40 KT 45 MPH

72H 27/0600Z 35 KT 40 MPH

96H 28/0600Z 30 KT 35 MPH...POST-TROP/REMNT LOW

120H 29/0600Z 25 KT 30 MPH...POST-TROP/REMNT LOW
Atlantic/2019/03L/Archive/4

With the aid of the oceanic diurnal maximum this morning atop the Gulf Stream, Tropical Depression Three gained a relatively impressive bout of convection, primarily on its eastern flanks, with a sizeable area of -60C and colder cloud tops. Based on reflectivity from the KMLB radar site, these are mostly associated with a strong band of embedded cells tracking away from the center. A US Air Force Reserve reconnaissance airplane has been investigating the system this morning and confirmed that the center of circulation is closed but ill-defined and displaced well west of the deepest convection. In fact, the center is virtually invisible to the KMLB radar just 40 miles away. Rrecon found SFMR-detected tropical storm-force winds right around the threshold intensity of 34 kt with flight-level winds topping out at 38 kt approximately 70 miles ENE of the center, but these are quite borderline and regressing away from the center of circulation. Winds are raised to 30 kt for this advisory, keeping 03L a tropical depression.
Despite the intensity and renewed convective activity, well-forecast by high-resolution guidance from mesoscale and hurricane models, 03L is doomed. 03L's circulation is quite small and, as is typical in the subtropics in July, entrenched in a high-pressure regime. The result is that the storm is extremely fickle and environment-sensitive as we saw with the virtually complete abatement of convection with last evening's diurnal minimum. While the waters are certainly warm and the environment more moist compared to yesterday, the anomalous frontal boundary sweeping across the United States is expected to blow the circulation apart and rive any organized convection later today into tomorrow. In fact, reconnaissance data suggests that this may be in process. By the time tomorrow's diurnal maximum hits, 03L will likely be no more and completely awash in the frontal complex, perhaps retaining a slight vorticity max. Until then, 03L is expected to continue tracking towards the north and later northeast as it flows along the low-level streamlines out ahead of the advancing front. This may be slightly optimistic, and dissipation may occur beforehand. A remnant low is anticipated by the next advisory.

FORECAST MAX WINDS
INIT 23/1500Z 30 KT 35 MPH
12H 24/0000Z 25 KT 30 MPH...POST-TROP/REMNT LOW