h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

1530Z Forecast August 2, 2006 for Tropical Storm Chris

== Current Conditions ==
Tropical Storm Chris is currently just to the north of the British Virgin Islands (65 miles|105 km north of St. Martin or about 19N, 63W as of 1200Z) and the intensity is set at 50 kt (57.5 mph|92.6 km/h) and is moving to the west northwest at 9 kt (10.4 mph|16.7 km/h)

An upper level feature that seems to resemble a developing eye has appeared on the long range radar out of San Jaun, Puerto Rico
http://radar.weather.gov/radar_lite.php?rid=jua&product=N0Z&loop=no
although this feature is located some 12 nm (13.8 mi|22.2 km) south west of the surface low pressure center. The local sea surface temperatures are around 28 C (82.4 F) (the generally accepted threshold temperature for intensification is 26 C (78.8 F) and values above 30 C (86 F) are considered to extremely favorable for intensification.

The current sea surface temperatures and related conditions can be found at
http://www.aoml.noaa.gov/phod/cyclone/data/at.html

== My Forecast ==
Track-wise, I'm forecasting Chris to pass north of the Carribean islands continuing on a west northwest track, pass over the southern end of the Bahamas, before taking a more westward track and passing just south of, or possibly passing over, the Florida Keys. I based this off of looking at the various model outputs for forecast tracks, the upperlevel streamlines, and the climatological track that storms in this situation tend to take (which is represented by the CLIPPER(CLP5) forecast track. The model outputs for the forecast tracks that apply to this prediction can be found at
http://euler.atmos.colostate.edu/~vigh/guidance/atlantic/store/early_AAL03_06080212.png


Intensity-wise, I'm expecting that Chris will intensify to a weak category one hurricane by sometime midday to late tommarrow at the latest. And looking further ahead, if it takes the track I'm forecasting, I'd expect that it will become a moderate to strong category one hurricane as it passes the Florida Keys. This scenario will be even more likely if the eye-like upperlevel feature and the low level circulation move so that they are aligned vertically (as opposed to the current situation where the low level circulation and the upper level eye feature are tilted to the southwest). On the other hand if Chris' track is not as far north as is expected, the storm will likely weaken due to the mountainous terrain of the greater antillies (such as Cuba). This prediction is based off of the local sea surface temperatures(SST), the 26 C SST Isotherm (in this case, this effectively represents the lowest depth where 26 C temperatures can be found, technically it's the depth at which the estimated sst is 26 C), the size of the storm (Chris, being a reletively small storm size-wise (which has nothing to do with current intensity), will change intensities (both increasing and decreasing) far easier than a larger storm), local geography, climatology, as well as model output intensity forecasts and the official forecast.

The model outputs for intesity that apply to this forecast can be found at
http://euler.atmos.colostate.edu/~vigh/guidance/atlantic/store/intensity_AAL03_06080212.png

== Official Forecast ==
The official forecast that was mainly referenced for this prediction was the 900 UTC (500 am EDT) advisory, the discussion in particular. In the time that it took me to make my forecasts (plus several interuptions of various sorts) the 1500 UTC (1100 am EDT) Advisory has been released and was also refered to for information, although there was not much change in the forecasts.

A list of official advisories for Chris can be found at
http://www.nhc.noaa.gov/archive/2006/CHRIS.shtml
and the latest advisories for the tropics (both atlantic and east pacific) can be found at
http://www.nhc.noaa.gov