Tuesday, May 5, 2015

No Major Changes Ahead...

By Jay Grymes & Steve Caparotta

May 5th First Alert Quickcast:

- isolated showers for Wednesday through Saturday
- an update on weather near Cuba and the Bahamas

Happy Cinco de Mayo!

As expected, it was a mainly-dry day today with just a few short-lived blips on our regional Doppler radar.  Highs climbed into the low to mid 80°s across the region for the afternoon. While dew points were in the low to mid 60°s, fairly persistent breezes through the afternoon kept the air reasonably comfortable, making for a nice May day.

Clouds will slowly increase late tonight and into Wednesday morning, with morning lows in the low to mid 60°s for most WAFB neighborhoods.

Wednesday will again be mostly dry across the area -- we’re going with a 20% chance of afternoon t-showers.  A modest mid-level “lid” on the atmosphere that inhibited showers today will weaken just a tad by Wednesday afternoon, allowing a few showers -- and even a pop or two of lightning -- to get going.  Like today, plan for highs in the low to mid 80°s for Wednesday afternoon around the region.  And like today, whatever showers do develop should be gone by sunset.

Our current forecast stays with spotty-to-isolated mainly afternoon showers for Thursday, Friday and Saturday -- rain chances at 20% or less each day.  However, a steady fetch off the Gulf will mean a slow increase in low-level humidity through the work week.  As the dew points rise, so will morning minimums.  In addition, the afternoons will get a tad warmer and more humid too. 

For Sunday, Mother’s Day, we think that the weather gets just a bit wetter: we’re posting a 30% rain chance for Mom’s afternoon.  Sunday won’t be a wash-out: more along the lines of a summer-type of day with hit-or-miss afternoon t-showers.  Stick with the BBQ plans.

The extended outlook into early next week features a cold front approaching from the northwest.  Yesterday’s guidance suggested a Monday arrival for the front.  However, today’s latest from the NWS Weather Prediction Center (WPC) delays the front until Tuesday.  The American GFS model is none-too-impressed by the front based on its latest rain projections, while the European ECMWF is a little more bullish with its rain forecast.  For the time being, let’s go with scattered rains for Monday and Tuesday.  We can fine-tune over the coming days.

So what about that broad area of messy weather extending from near Cuba to near the Bahamas?  Yesterday, the National Hurricane Center (NHC) gave the region a 30% (low) chance of development during the latter half of this week.  Today, the NHC ‘upped’ the 5-day chance of development to 40%, adding in a 20% chance for the next two days.

So what does all this mean?  Well, we could have a pre-season ‘Ana’ on the tropical board by the weekend.  Virtually all of the computer models are showing some type of low developing, although they differ in terms of intensity and location. 

Most importantly for our local interests: no matter what happens, this is not going to be a threat for us.

If you’ve been watching the satellite presentation over the past 24 hours or so, two things are apparent:  (1) while there are some guesses, there does not appear to be a clear-cut surface low anywhere in that mess and (2) there is a fair amount of SW-to-NE flow aloft.

Now, if this were a tropical system, those upper-level winds would be counter-productive.  But the consensus thinking is that any surface low that forms will be non-tropical, at least in the initial phase.  If that is the case, the upper-level winds might actually be beneficial by enhancing the vertical lift and deepening the low. 

The question then becomes, should a non-tropical low form, could it then start to morph into a sub-tropical (hybrid) system?

When we go back to the computer models, the answer appears to be leaning somewhere between possible to likely.  In other words, we’re still far from a sure thing here, but if the non-tropical low could form, drift north and then meander over the warm Gulf Stream waters, then we could have a set-up for a slow transition to something sub-tropical. 

The NHC still has an aircraft scheduled to visit the region tomorrow, although an official “invest” (area of investigation) has yet to be declared as of this writing.  Stay tuned!

No comments:

Post a Comment