Although these forecasts have been shown reliable, first consult and consider official products released by the National Hurricane Center.

...Danielle maintains strength; about to enter heavy shear...

...Based on 1515 UTC images...

T-numbers sit at 5.0 through today, and satellite presentation remains excellent, with a definite eye appearing clearly on visible images. The northern portions of the hurricane are being affected by flow from an upper level low to the immediate northwest of the hurricane. Danielle will move northward around a weakened subtropical ridge, whose center will move about Danielle and the upper level low, then steer the hurricane to the northeast and east-northeast until it becomes extratropical. The track forecast is a little right of the previous forecast based on forward motion, and recent images indicate that Danielle is turning more toward the north instead of north-northwest; therefore, the storm is turning closely to that indicated in the previous track forecast. Intensity forecast will immediately weaken the storm, as it moves into an area of vertical shear of 35kts or greater, and as it moves into cooler waters toward the later parts of the forecast period. The intensity forecast will maintain a hurricane through 36 hours, and allow for steady weakening through 120 hours; however, shear will relax a little as Danielle moves northeastward and east-northeastward away from the upper level low, so weakening is modest after 48 hours.

INIT 24.1N 40.2W 90KTS
12HR 26.4N 40.8W 85KTS
24HR 28.7N 40.7W 75KTS
36HR 31.1N 40.0W 65KTS
48HR 32.9N 38.9W 55KTS
72HR 35.2N 35.5W 50KTS
96HR 37.1N 31.7W 45KTS
120HR 45.8N 21.6W 40KTS...EXTRATROPICAL

Powell

...Danielle maintains intensity as it moves northwest...

T-numbers remain at 5.0 this morning, corresponding to 90kts, and satellite presentation remains excellent. The initial intensity is set at 90kts. Danielle has move northwestward much quicker than anticipated in previous forecasts, so this forecast will adjust and take Danielle northwest immediately off of forward motion and somewhat parallel the last forecast, except that changes in motion will occur sooner. The track forecast carries the system around a mid-level ridge, and brings the subtropical ridge around the hurricane, taking the hurricane northeast after 72 hours, and making the turn around the north side of the ridge through the end of the forecast period. Increased shear values from a trough across the Atlantic to the hurricane's northwest and cooler SSTs will cause some weakening in higher northern latitudes. In addition, dry air may become entrained in Danielle's center, should southwesterly shear become a major factor in weakening, as much dry air sits to the west and northwest of the storm.

INIT 18.6N 37.2W 90KTS
12HR 19.3N 38.8W 90KTS
24HR 21.5N 40.0W 85KTS
36HR 23.9N 40.7W 80KTS
48HR 26.5N 40.8W 70KTS
72HR 31.1N 39.7W 60KTS
96HR 34.8N 36.6W 50KTS
120HR 37.1N 31.9W 50KTS

Powell

...Danielle continues to intensify quickly...

Initial position was missed a little; however, the forward speed of Danielle initial was tacked down. Satellite images indicate that Danielle continue to intensify, and T-numbers range from 4.0 to 4.5, so I will split the difference and set initial intensity at 75kts.

Track forecast reasoning remains the same; however, forward motion brings the track a little left and a bit faster initially, and slower at the end. A mid-level ridge controls the movement of Danielle, which is currently a minor touch left of the previous forecast track. I imagine that forward speed will increase a bit as Danielle intensifies and moves farther northward around the edge of the mid-level ridge. Model guidance continues to suggest that the strong subtropical ridge will weaken between 72 and 96 hours, thus eliminating the chance for Danielle to continue westward. The ridge will weaken in response to a trough that will move across the Atlantic over the next several days, and it will lift Danielle northward through the end of the forecast period. But after 96 hours, the track forecast is a little more complex. Currently, a low pressure system near 32N 35W is spinning with a deepening trough draped across the Atlantic between 38N and its apex at 26N 42W. This trough will move out of the region at the end of the forecast period; therefore, the slower movement indicated at the end of the forecast period in the previous forecasts is simply extended into this forecast, calling for a slow north-northwestward drift around the mid-level ridge. In addition, after 5 to 6 days, the Atlantic subtropical ridge will begin to strengthen, but model guidance suggests that the ridge will re-position to the southeast near the current position of the mid-level ridge, and the hurricane and the ridge would rotate around one another. A new ridge is also suggested over the far North Atlantic. Thus, the official forecast take Danielle northward at the end of the forecast period, but insinuates a turn to the northeast shortly thereafter, with an increase in forward speed.

Shear values will remain low through the initial 48 hours, and Danielle will remain over warm waters, with SSTs around 27C. Therefore, signiificant intensification is expected through 2 days. Danielle is intensifying at the rate suggested last night--perhaps a little faster, but this is only through 12 hours; I will intensify the storm to a major hurricane peaking at 100kts in 48 hours. Afterward, shear values will begin to increase in association with the trough that will pick up Danielle, and the track will move the hurricane over water. Steady but modest weakening is forecsat between 48 and 96 hours as shear values become unfavorable. However, as shear begins to relax after 96 hours, the weakening trend will slow; however, Danielle will remain over cooler waters--enough to sustain a storm, but not likely to intensify it.

INIT 14.5N 33.0W 75KTS
12HR 14.7N 35.7W 85KTS
24HR 15.4N 38.6W 90KTS
36HR 16.6N 41.2W 95KTS
48HR 17.8N 43.8W 100KTS
72HR 21.3N 46.9W 90KTS
96HR 29.9N 48.3W 80KTS
120HR 27.8N 48.4W 75KTS

Experimental Shear/Dry Air Model (See information here.)

INIT 980mb
12HR 974mb
24HR 968mb
36HR 962mb
48HR 957mb
72HR SSTs
96HR SSTs
120HR SSTs

Powell

...Danielle nearly a hurricane...

Pressures have dropped this evening, and Danielle appears excellent on satellite. T-numbers range up to 4.0, which would correspond to 65kts and a Category 1 hurricane, but I am inclined to wait a few more hours before I classify as a hurricane, because one way or the other, intensification is expected. Therefore, I will set initial intensity at 60kts for tonight's forecast.

Danielle is right on track of the forecast issued this morning, so this forecast is basically an extension of the previous forecast. Danielle will ride under a strong mid-level ridge in the eastern Atlantic, which will turn it northwestward at about 72 hours as the hurricane reaches the southwest portion of the ridge and as the main subtropical ridge weakens significantly. The mid-level ridge will maintain its dominance throughout the forecast period, superceding the subtropical ridge so to speak, and force the storm northwestward. This forecast is faster than the previous forecast after 72 hours, since the subtropical ridge is forecast to weaken faster than previously expected, thus ending a general westward movement.

Intensity forecast is based on track, since shear remains low over the area, but SSTs are cooler along the forecasted track. However, the intensity forecast is moderate through 36 hours, then levels off as the hurricane moves into waters between 26 and 27C after 72 hours particularly. Toward the end of the forecast period, the potential for shear will increase via a jet riding over the mid-level trough. Weakening is forecast between 96 and 120 hours, and the storm is expected to peak around 96 hours--this forecast places the intensity at 90kts at 48 hours.

INIT 14.0N 29.4W 60KTS
12HR 14.5N 31.6W 70KTS
24HR 15.0N 33.9W 80KTS
36HR 15.5N 36.3W 85KTS
48HR 16.0N 39.1W 90KTS
72HR 18.9N 42.8W 90KTS
96HR 23.0N 45.6W 85KTS
120HR 27.3N 48.3W 75KTS

Powell

...Danielle moving west-northwest...

T-numbers have increased to 2.5 and 3.0, and satellite appearance looks a little better. Based on this initial intensity is 40kts.

Danielle has moved a bit slower than expected in the previous forecast, and has taken a more northerly angle than expected--rather than an extension of its forward motion from yesterday. Because of this the track forecast is shifted to the right initially, but I believe that the current track is due to a weakness in the southeastern portion of the ridge--thus explaining both the slow motion, and the northward component. After about 24 hours, the track forecast parallels that from last night until 72 hours. Model guidance agrees that the subtropical ridge will significantly weaken in about 72 hours, and Charley should then be able to move around a mid-level ridge set into place across the eastern Atlantic. Although models do not initiate and maintain the storm very well, the track forecast follows this reasoning and allows for a turn to the northwest after 72 hours.

Due to the northward shift of the forecast, the storm will be over cooler waters than forecast, about 26C rather than 27C, so the intensity forecast is less aggressive. These waters can maintain a hurricane, but are not likely to quickly intensify one. The forecast still calls for a hurricane through 72 hours, but levels off afterward, as the system moves northward. Due to the potential of shear as Danielle moves around the ridge, I will call for weakening at 120 hours, taking Danielle back to a tropical storm. However, this forecast will take about 24 hours to pan out--but much intensification is not expected after the storm turns northwest.

INIT 13.4N 26.8W 40KTS
12HR 13.9N 28.7W 45KTS
24HR 14.5N 30.7W 50KTS
36HR 15.0N 33.0W 55KTS
48HR 15.5N 35.5W 60KTS
72HR 16.5N 40.6W 65KTS
96HR 18.7N 44.2W 65KTS
120HR 22.1N 46.9W 60KTS

Experimental Shear/Dry Air Model (See information here.)

no-run (SSTs)

Powell

...Tropical storm continues westward...

...Based on 0000 UTC images, and fixed for 0100 UTC...

A QuikSCAT pass from late afternoon indicated that the system has a more clearly defined center of circulation than it did this morning, and 35kt winds are still indicated at the surface--and now more widespread. I will set initial intensity at 35kts; although T-numbers remain at 2.0, indicating a 30kt depression.

The track forecast is rather straightforward. The system will continue west-northwestward under the influence of the Atlantic subtropical ridge. As the storm moves farther north, the gradient between the system and ridge will increase, and the forward speed of the storm will increase, particularly from 72 hours on. This is indicated in the official forecast, which takes the storm a little more westward toward the end of the forecast period, as the west side of the ridge builds back in from a trough and two disturbances that are currently cutting the ridge off. Intensity forecast is aggressive, since shear values will remain low--vertical shear about 10kts, and surface shear starting between 10 and 15kts, and decreasing to 10kts by the end of the forecast period. SSTs will range from 26C to 28C in the margin of error, and I will allow for a hurricane at 72 hours. On the flip side, the north side of the storm looks a little more unhealthy tonight, and infrared indicates that deeper convection has lightened up a bit. So I will allow for the system to maintain a pulse before intensifying too aggressively. An SSMI pass from this evening did suggest that the center was not exposed; however, the pass did not cover the entire center.

The track forecast is basically an extension of the previous forecast; however, it is pushed to the right a little after 72 hours to correspond with model guidance.

INIT 12.7N 25.0W 35KTS
12HR 13.2N 27.5W 40KTS
24HR 13.7N 30.0W 45KTS
36HR 14.2N 32.9W 50KTS
48HR 14.9N 34.9W 60KTS
72HR 16.1N 41.6W 70KTS
96HR 17.2N 47.5W 80KTS
120HR 18.3N 53.9W 90KTS

Experimental Shear/Dry Air Model (See information here.)

INIT 1009mb
12HR 1005mb
24HR 1001mb
36HR 996mb
48HR 991mb
72HR 979mb
96HR 971mb
120HR 963mb

Powell

...Tropical storm form southeast of Cape Verde Islands...

Although these forecasts have been shown reliable, first consult and consider official products released by the National Hurricane Center.

QuikSCAT passes from earlier this morning indicated a 40kt barb admist 30kt barbs, and T-numbers are 2.0, coinciding with 30kts. I will split the difference for this forecast and set initial intensity at 35kts, making the system a tropical storm.

Track forecast is fairly straightforward; the Atlantic subtropical ridge will act as the primary steering current for the system throughout the forecast period. Model guidance suggests that the ridge will remain intact, and thus the forecast will maintain a steady west-northwestward movement throughout the forecast period. Current movement is 12 knots to the west-northwest, and this motion will increase in this direction as the storm comes under the stronger influence of the subtropical ridge. The track forecast reflects this, and brings the storm to between 50 and 55 degrees longitude roughly in 120 hours. Surface shear ahead of the storm is light, varying from 5 to 15 knots through much of the central and eastward Atlantic, with vertical shear excluding movement is about equal. This should allow for conditions that are favorable for development, and SSTs are favorable for development through the track of the forecast, and the SAL should only act as a marginal issue for this storm. Steady intensification is expected throughout the forecast period, and the forecast calls for a hurricane in 72 hours, maintaining a Category 1 hurricane throughout the forecast period.

I'd prefer to wait for model guidance to pick up the system a litle better, perhaps, when a more clear circulation forms; then the track forecast will be a little more straightforward. For now, I will set with the models initially.

INIT 12.2N 22.7W 35KTS
12HR 12.8N 25.1W 40KTS
24HR 13.2N 27.6W 45KTS
36HR 13.8N 30.1W 50KTS
48HR 14.2N 33.1W 55KTS
72HR 15.2N 39.0W 65KTS
96HR 15.9N 44.9W 75KTS
120HR 16.5N 50.9W 80KTS

Powell

...Tropical Depression forms in East Atlantic...

...Based on 1200 UTC images and fixed to locate center...

QuikSCAT images indicates that winds have reached 40kts, and T-numbers sit around 2.0--the system will compromise the two, and allow for 35kts initial intensity. Satellite presentation is excellent this morning. The ill-defined center of the storm was located near 13.0N 23.3W, and the storm is moving westward and will continue to do so generally through several days.

First forecast will be issued around 1PM.

Powell