NOAA will release its forecast for the 2010 Atlantic Hurricane Season during a press conference this morning at 10 AM. We will have it for you coming up on WINK News Now on 6 TV at 11 AM; I hope you can join us. Most likely, the forecast will be for a very active hurricane season, quite possibly more active than the latest Colorado State forecast of 15 named storms, 8 hurricanes, and 4 major (Category 3-5) hurricanes. Why are we expecting an active season?
There are multiple reasons but one of the biggest is the rapid retreat of the warm phase of ENSO (El Nino-Southern Oscillation) observed over the last several weeks. The top animation is the sea surface temperature anomaly across the equatorial Pacific Ocean. Notice the rapid transition from bright red colors in the center part of the animation (indicating sea surface temps 2-3C above average) to light blue colors (indicating slightly below average sea surface temperatures)! Most of the equatorial Pacific now features either average or below average SST's -- indicating a chance we could be headed for a La Nina by the heart of the Atlantic hurricane season. This is important because La Nina's are associated with much weaker wind shear in the Atlantic basin while El Nino's feature stronger shear (like we saw during the 2009 season).
Couple that with the second image I have posted, the Tropical Cyclone Heat Potential (essentially, the depth of warm water in the tropical Atlantic), and the Atlantic is ripe for a big season. TCHP is running very high across the Caribbean and much of the lower latitudes in the Atlantic for this time of year, definitely a major concern as we approach the heart of the season (remember, deep/warm water is the fuel source for hurricanes).
What about the Atlantic low?
In Image 3, I have posted the water vapor view from this morning of the Atlantic low, which is now starting to pull away from the east coast. The atmosphere around it has moistened substantially versus the past few days and there are now disorganized clusters of thunderstorms encircling the center of circulation. The wind shear is light and the water, for a while longer, is warm enough to support subtropical development. In fact, some satellite measurements yesterday indicated that the storm had indeed gone warm core (warmer temps at the center of the low rather than outside the low; a cold season low is "cold core," colder near the center of the low) -- this suggests that loosely we could have called it a subtropical storm yesterday based on the temperature pattern and the gale force wind surrounding it. The NHC didn't so, officially, it goes down as a regular area of low pressure.
Is there anything else worth watching in the tropics?
The other area worth watching is in the far eastern Pacific, a system (Image 4), the NHC is giving a 50% chance of developing into a tropical depression over the next day or two. It's located in an area of fairly weak wind shear and warm enough water -- however, that water off the west coast of Central America is not particularly deep (thus that Tropical Cyclone Heat Potential map shows cooler colors there compared to the Caribbean). We'll have to wait and see on development here but some of the models do carry some energy from this into the western Caribbean into an area that might be favorable for development early next week. Anything that were to get into the western Caribbean though would likely be carried well south of the Florida Straits with a strong subtropical jetstream.
I'll update this blog with the NOAA forecast numbers coming up later this morning!
Brian
