Thursday, June 13, 2013

Late June/Early July Holds Tropical Threat

Latest indications are that the next tropical threat could arise in late June into early July, and that this threat could be more formidable than when Andrea formed.

The long range forecast over the seven day period from June 20 to June 27 depicted above shows upper level divergence anomalies. Areas of green depict below normal anomalies and thus increased chances for enhanced tropical convection, while above normal anomalies signal a less favorable environment for tropical convection. The GFS Ensembles project these divergence anomalies to drop into the below-normal range and increase the risk of tropical cyclone formation. This would supposedly be associated with a Madden-Julian Oscillation (MJO) wave making its way to phases that are favorable for tropical cyclone formation. However, a comparison to other models suggests that the GFS Ensembles may be a bit too fast with the movement of this MJO wave into favorable phases, and that is why early July remains on the table for timing.

The GFS Ensembles, between June 23 and June 28, then predict a large swath of the Gulf of Mexico to be under the influence of rather substantial low mean sea level pressure (MSLP) anomalies. This would seem to indicate the willingness of the GFS Ensembles to attempt and formulate an environment favorable for tropical cyclone formation. Towards the end of this particular GFS Ensemble run, the SLP anomalies are even lower than what is shown above, leading me to believe there is a growing consensus that late June into early July is a reasonable timeframe for the Atlantic basin's second shot at tropical cyclone formation. Support by the aforementioned MJO wave would make this second shot the more formidable of the two.



Anonymous said...

In reference to your facebook post about how the forecasts went wrong, i can assure you that when there were winds of at least 60 miles per hour, the tornado sirens were going off, and there was rotation spotted in my town, there was no false forecasting in that. They put me in the ''High Risk" for those threats and they certainly were not wrong. Just because your town was not hit hard by the storms doesn't mean there was not severe weather elsewhere. Just because there is a high risk doesn't mean everyone in it will get pounded into the ground with a sledgehammer and have their trees chopped down like Paul Bunyan and the Blue Ox came through town riding in a GMC Sierra Denali with leather Interior.

Andrew said...

It sounds like you were on the other end of the scale- the one that got the worst weather. Remember that the high risk was issued on account of an extreme damaging wind risk and not the tornado threat- the lack of multiple significant damaging wind reports tells the story- the high risk did not verify.

Anonymous said...

It is now confirmed the my county ( Porter county ) had a macroburt with winds from 100-110mph so we did have strong winds.

Andrew said...

Again, it sounds like you were at the other end of the scale- the one that got weather worthy of the High Risk. However, the majority of people in the High Risk did not receive weather deemed appropriate for the High risk outlook.