30-Day Weather Outlook for July 27 to August 27, 2024

Jul 31, 2024

BASIC PATTERN:

Large Scale Pattern

The focus of lingering upper troughs continues west of the Pacific Northwest, and troughing at 135-160W, and high pressure to the west but near to southern California (SOCAL). High pressure aloft develops at times across central California in this pattern.
A cooler pattern develops at times into Central and Northern California with deeper marine layer, and drizzle at the coast about Monterey northward.
Our IVTinitô analysis shows the calculated estimate of one day (Day 0) Total Integrated Vapor Transport (TIVT24), based on the sea surface temperature anomaly pattern from the coast out the Dateline-180W. This is calculated by Fox Weather LLC ís CyclogenIVT AI application each day. It shows for us the potential areas for development of troughs and rains upstream from California and the West Coast. Physical units of TIVT are the same as for 24 hour TIVT from the Center for Western Weather and Water Extremes (CW3E).
For forestry and the remainder of Fire Season 2024 in NORCAL and Sierras with the bottom line: recurring hot periods and below average precipitation.
Tropical cyclones are a regular feature across S Mexico and SW of Baja. Tropical cyclones in summer teleconnect with well above average temperatures for California, in general. Tropical cyclone remnants will head WNW from the tip of Southern Baja California, steered by high pressure aloft over the eastern North Pacific near or west of California and in deserts region of the Southwest US.

Forecast for N California

NORCAL Precipitation: A few thunderstorms (TSTMS) July 22-23 Sierras, Aug 8-9 N and Central Sierra, and a few more TSTMS on Aug 21-24 most mountain areas.
NORCAL Hot-Dry Periods: Jul 25, Aug 1-7, 12-16 and 25
NORCAL Mild and Breezy Periods: Jul 27, Aug 9-10, 18-19 and 21-24.
North Sierra Precipitation Jul 23-24, 31-Aug 1, 4-7, 15-16 and 22-25
Central Sierra Precipitation Jul 24-25, Aug 1-2, 5-7, 16 and 23-25.

Forecast for Central California

Central Calif Precipitation: Dry with rain unlikely W of Sierras.
Central Calif Hot Periods: Jul 22-26, Aug 1-7, 12-17 and 21-25
Central Calif Mild Periods: Jul 27-28, Aug 9-10, 19 and 26-28

Forecast for S California
SOCAL RAINS: Jul 27-28, Aug 4-5(east deserts), Aug 7-8 mountains/deserts.
SOCAL HOT PERIODS:Jul 23-26, 29-30, Aug 1-3, 10-15, 19-21 and 26-28
SOCAL Mild Periods: Jul 27-28, 31, Aug 7-9, 16-18 and 22-25.

---------

The listings of dates normally included for hot and cold spells, and precipitation are approximate. They are based on GFS and our CFSDaily and CFSDailyAI products; and present expected trends in precipitation and temperature (FoxCFSDailyAI) to 5km. Our AI system gives some consideration to terrain and coastal influence. Although we consider the CFSv2 one of the better ways to represent basic weather in the sub-monthly time scale, performance of the CFSDaily. CFSv2 daily products during storm seasons has been especially inconsistent and difficult to apply to the useful criterion needed by cropland agriculture, and viticulture beyond the 15ñday GFS.

---------

Looking Ahead — Longer Range Outlook

Southern California Deserts Outlook
SOCAL deserts: above normal temperatures, and below normal rainfall for the period.

N and Central California and Sierras
Above average temperature overall, with recurrent very hot spells during most of August. Rainfall will recover to near average in Aug. Sept 2024 appears dry and hot. Again, this suggests thunderstorms (TSTMS) in the N and Central Sierras.
For Southern California away from the coastal influence area, we look for above average temperature overall; including hot spells in August. Rainfall will remain below average with the usual mountain/desert TSTMS. In Sept we currently appear to have above average temperature but below average precipitation in both NORCAL/Sierras ,and in Central to Southern California.

Monsoonal Conditions

Tropical cyclones will continue to focus in the ocean area south of Mexico. Despite the dry anomaly, monsoonal moisture and thunderstorm conditions may occur a few times during tropical cyclone season due to easterly waves in SOCAL. For the Outlook portion August - October the monsoon appears to to have mostly lower than average rain amounts in Sierras and SOCAL mountains/Deserts for Sep and Oct.

Looking Farther Ahead

California temperatures appear to return to above normal during October, while precipitation is below average for that month. It turns cooler after mid Oct, with rains starting to develop North Coast from Mendocino Co northward by end of Oct.
Nov appears to be warmer than average, but with above average. Precipitation focusing on far NW California northward. This may suggest early season Atmospheric River activity into far NW California in Nov.

(Terms and Definitions Used In This Weather Outlook)