Weather Briefing, 20070718

Contributions from Lenny Pfister, Erick Rivera, Chuck Bardeen, Karen Rosenlof, Berny Fallas, and Eric Ray

Where is the Tropical Wave!?

• The NHC shows on the last surface analysis that the wave passed over the country between yesterday and first hours of today

• The analysis done by IMN on Monday showed the wave passage as is shown by NHC today.

Where is the Tropical Wave!?

The 00Z and 06Z run have the same pattern as yesterday with the weakening of easterlies , this is the

00Z, the blue line again is the Precipitable Water

06Z Run

• Today, GFS and NHC do not show any wave moving over CR on thursday.

• With wave or not wave the forecast do not change, there will be a shift in the winds at the airport on Thursday.

• If the westerlies delay (come to the airport after 1 pm) entering the Valley, there are high probabilities of convection west of the airport.

• Thinking that convection in the Caribbean will not bring cirrus to the Valley, Thursday seems like a typical day with rains after 2 pm at the Airport.

The following three slides show winds and precip at 925 mb. As we go from early tomorrow (July 19) to July 20, the easterlies over San Jose weaken. This coincidesWith a movement of the convergent zone at 925 mb fromWell south of SJO’s latitude to a latitude more near ourLocation. The result is a higher probability of significantPM rains at our location.

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Model Results

• CIGEFI MM5

• CIGEFI

• GEOS-5

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Comments on model results

• CIGEFI and GFS roughly agree on locating some convection along Guatemalan coast and along the ITCZ at roughly 8N or so.

• GEOS model has major convection located closer to south Costa Rican coast.

• My (LP) and Berny’s assessment is that the convection near Guatemala is possible based on wave passage. ITCZ convection away from CR also seems reasonable