Coredesat's SubTD Andrea forecasts - Last one

[Coredesat]

Since I have a blog for these, I'll post my discussions and track maps from the blog.

DISCLAIMER: The following posts are not an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org. For official information please refer to the NHC and NWS products.

Well, here it is - Subtropical Storm Andrea has arrived, though under weird circumstances. The system has slowed down further, leaving me unable to estimate how slowly it is moving. According to Forecaster Knabb of the National Hurricane Center, Air Force recon found a borderline warm/cold core, which confirmed what the cyclone phase models and AMSU imagery indiciated. The convective structure has not changed much, although convection in the SE quadrant has deepened a little and the convection is a little closer to the center. Latest SAB satellite fix was ST3.0 using the Hebert-Poteat technique for estimating subtropical cyclone intensity.

The models aren't being kind to me this morning given Andrea's slow initial motion. Most of them have Andrea drifting to the southwest, then to the south over the next few days. About half of the models (namely the ETA, NOGAPS, BAMS, GFDL, and the NCEP GFS ensemble) bring Andrea over land at some point in the forecast period, and there is no reason to believe that it won't make landfall after 72 hours. Thus, the forecast indicates a southwesterly to southerly drift. The system is currently over the warmest waters it will encounter on this track, so weakening is likely.

Initial...31.0°N 79.5°W...40 kt
12 hour...30.8°N 79.8°W...40 kt
24 hour...30.5°N 80.1°W...35 kt
36 hour...30.2°N 80.3°W...35 kt
48 hour...29.7°N 80.4°W...30 kt
72 hour...29.2°N 80.5°W...30 kt

[Tampa Bay Hurricane]

Intriguing...as i say i love reading forecasts of this
stuff! Good forecast!

[cycloneye]

That is a good forecast from you my friend.

[JonathanBelles]

I like the map and the forecast.

[Coredesat]

Thanks, guys. I've put a lot of work into this over the past few months in order to make things easier to read, yet look a little more professional while still remaining amateur.

I post forecasts every 12 hours, in general.

[Rainband]

Good Job

[Coredesat]

Forecast #2

Andrea is really not looking very healthy on satellite imagery this evening. SAB water vapor imagery shows the western half of the system full of dry air and devoid of convection. Almost all of the convection is in the southeastern quadrant of the circulation. The center is very difficult to pinpoint and is estimated based on QuikSCAT data. SAB satellite fixes have dropped to ST1.5 using the Hebert-Poteat technique, and I have lowered my forecast intensity to 35 kt.

Given the increasingly hostile environment around it, Andrea may not survive until the end of my 72-hour forecast period. The model guidance has not shifted much since the previous forecast, although the GFDL now takes the system (or its remannts) southeastward and out to sea. Most of it agrees with a general southward drift, which is reflected in the forecast. However, the models also forecast Andrea to maintain its intensity throughout the next 120 hours, which I really can't see happening given how badly the dry air is affecting the system. This forecast will call for continued weakening to a remnant low by the end of the forecast period.

Initial...30.9°N 79.6°W...35 kt
12 hour...30.8°N 79.7°W...30 kt
24 hour...30.7°N 79.8°W...30 kt
36 hour...30.5°N 79.9°W...25 kt
48 hour...30.3°N 80.0°W...25 kt...dissipating
72 hour...29.9°N 80.1°W...20 kt...remnant low

[Coredesat]

Repeating the disclaimer: The following posts are not an official forecast and should not be used as such. They are just the opinions of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution including storm2k.org. For official information please refer to the NHC and NWS products.

Forecast #3

After a rough night in which the center became completely exposed, Andrea has been reduced to a mostly non-convective cloud swirl with a few patches of scattered convection about 3° northeast of the center. Water vapor imagery shows that it is impossible to distinguish Andrea's circulation from the rest of the environment, except for these tiny patches of convection - that much dry air has entrained itself into the circulation. Air Force recon did not find any flight-level winds that support subtropical storm strength, so the intensity is reduced to 30 kt based on QuikSCAT imagery and a guess that there are some 30 kt winds occurring in those tiny pockets of convection. Latest SAB satellite fix was ST1.5.

The model guidance is again similar to the previous runs - little movement in the next 2-3 days. However, most of the models (excepting the NOGAPS) send Andrea or whatever is left of it off to the northeast as an extratropical cyclone. Seeing as even extratropical cyclones have convection, I'm not sure that is going to happen, and will call for continued weakening and a southward drift. Andrea should degenerate into a remnant low later today or tomorrow.

Initial...30.0°N 80.1°W...30 kt
12 hour...29.7°N 80.1°W...25 kt...remnant low
24 hour...29.4°N 80.0°W...20 kt...remnant low
36 hour...dissipated

[Coredesat]

The remaining convection associated with Andrea has died away throughout the day, leaving a mostly naked swirl of low clouds east of Daytona Beach, Florida. The circulation is impossible to discern on water vapor imagery, but is quite easy to see on infrared satellite imagery. The center is well-defined, but as mentioned before the system is nearly devoid of convection, save for a couple patches of very shallow convection in the southeast quadrant of the system. SAB fixes remain ST1.5, although without convection the system is essentially unclassifiable. I am now considering Andrea a remnant low, though it has probably been one for a few hours now.

Most of the models have the remnant low performing a small loop to the southeast, then moving off to the northeast as it interacts with an extratropical system off the East Coast of the United States. This is reasonable, but no matter what happens, there will probably be nothing left of the low after 24 hours or so.

Initial...29.2°N 79.9°W...30 kt...remnant low
12 hour...28.7°N 79.7°W...20 kt...remnant low
24 hour...dissipated