300 UTC 4/21/2003 Subtropical Storm Ana Forecast Discussion #1

This is an independent product and not from the National Hurricane Center.

Subtropical Storm Ana has been moving slowly this evening and mainly to the east. This has been in response to an approaching trough to its west. There is no reason to think that the system will not continue moving to the east and turn to the ENE over the next day or so as the system will feel the effects of the approaching trough. The models agree with this scenario and so does this forecast. This will take the system passed Bermuda within the next 24 hours, if everything goes according to forecast.

The intensity forecast is very tricky. The initial intensity of 35KT is based upon satellite estimates as well as QUIKSCAT data. SHIPS indicates weakening along with GFDL. SHIPS is heavily weighted by how many days removed from the peak of the hurricane season it is, so this solution can be somewhat discounted for now. GFDL also indicates weakening. I prefer to be a bit more cautious and indicate no change in intensity through the next 36 hours. This is out of respect of the guidance and the fact that some systems can intensify under this environment (underneath an upper low with a trough approaching, despite being over cool water). Based upon this, the greatest impact on Bermuda will be squally weather.

Note: The 2002 forecasting guidelines will remain in place until May 15. Therefore, there will be no 5-day forecast, or a graphical version of the forecast at this time.

Initial: 31.4N 66.3W 35KT
12 Hour: 31.5N 65.1W 35KT
24 Hour: 32.0N 64.0W 35KT
36 Hour: 33.2N 62.0W 35KT
48 Hour: Absorbed

Forecaster: Ortt

1500 UTC 4/21/2003 Subtropical Storm Ana Forecast Discussion #2

This is an independent product and not from the National Hurricane Center

Ana is moving with the westerlies and the long trough it is embedded in. The motion has been to the south of the previous forecast and faster. Guidance indicates that Ana will turn back to the east, then ENE. This forecast also reflects this and increases the speed from the last one.

The initial intensity is being kept at 35KT due to satellite estimates. The deep convection is minimal. Therefore, no further intensification is being indicated until the system merges with the approaching trough in about 36 hours.

Initial: 29.8N 64.2W 35KT
12 Hour: 29.6N 62.0W 35KT
24 Hour: 30.3N 58.5W 35KT
36 Hour: Absorbed

Forecaster: Ortt

300 UTC 4/22/2003 Subtropical Storm Ana Forecast Discussion #3

This is an independent product and not from the National Hurricane Center

Ana has continued its trend of moving faster than the forecast has indicated. The westerlies have captured Ana. The motion to the south of due east should soon end and turn to the ENE as has been forecast. This track is a bit faster than the previous ones and is along the same general track as the previous forecasts.

The initial intensity is being kept at 35KT. This is based upon satellite estimates. No change in intensity is anticipated until Ana either merges or becomes extra-tropical. Extra-tropical transition now seems like a possibility as the system is more removed from the surrounding baroclinic systems than anticipated. Ana may in fact be a tropical storm at this time. Satellite estimates are being made with the Dvorak Technique instead of the Herbert-Poteat Technique. However, for now, Ana will remain a subtropical storm. Any changes will be made in a post season report.

Initial: 29.4N 60.4W 35KT
12 Hour: 29.7N 55.5W 35KT
24 Hour: 31.5N 46.7W 35KT
36 Hour: Absorbed

Forecaster: Ortt

1500 UTC 4/22/2003 Subtropical Storm Ana Forecast Discussion #4

This is an independent product and not from the National Hurricane Center

Ana has been captured. The storm is being steered to the east by the upper low to its north and by the approaching longwave trough. Ana should soon make the anticipated turn to the NE with continued acceleration. If Ana survives more than 36 hours, a NNE track is likely.

Initial intensity is being raised to 40KT, based upon uncontaminated QUIKSCAT barbs indicating 45KT. I have chosen to keep the winds lower due to the poor satellite appearance. No change in intensity is being reflected until the extra-tropical transition.

Initial: 29.8N 57.8W 40KT
12 Hour: 30.4N 51.0W 40KT
24 Hour: 31.9N 45.0W 40KT
36 Hour: Extra-Tropical

Forecaster: Ortt

300 UTC 4/23/2002 Subtropical Storm Ana Forecast Discussion #5

This is an independent product and not from the National Hurricane Center

Ana is moving along the previous forecast track, though the problems with the forward speed continue. Ana has been moving near 17KT to the east. The storm is accelerating, so not many changes will be made to the next forecast. Ana should move around the upper low to its north, though not ever turning to the north as the upper low is being pushed to the east due to the longwave trough approaching from the west. The guidance agrees with this scenario.

The initial intensity remains at 40KT based upon satellite estimates. No change in the intensity will be indicated in this forecast until Ana makes the extra-tropical transition. Due to the fact that Ana has lasted longer than anticipated as a classifiable cyclone, forecast points will be included through 48 hours with this forecast, even though it is extremely unlikely that Ana will actually remain a subtropical cyclone through 48 hours.

Initial: 30.2N 53.7W 40KT
12 Hour: 31.2N 47.5W 40KT
24 Hour: 32.5N 41.0W 40KT
36 Hour: 34.0N 34.0W 40KT
48 Hour: 36.5N 26.5W 40KT
72 Hour: Extra-Tropical

Forecaster: Ortt

1500 UTC 4/23/2003 Remnants of Ana Forecast Discussion #6

This is an independent product and not form the National Hurricane Center

Morning satellite imagery indicates that the low-level center has become much larger and removed from the deep convection, which has been sheared well to the northeast of the center. In addition, the convection is rapidly losing its curved banding structure. Therefore, Ana is being declared to have made the transition into an extra-tropical cyclone at this time. Now that Ana is a shallow system, it should move slower than previously forecast.

There should not be much intensity change with Ana as it will maintain its intensity through baroclinic means.

No track or intensity forecast is provided with this discussion.

Forecaster: Ortt

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